Co-reporter:Chi Hu, Yang Lan, Feng Tian, Kevin R. West, and Oren A. Scherman
Langmuir September 16, 2014 Volume 30(Issue 36) pp:10926-10932
Publication Date(Web):August 29, 2014
DOI:10.1021/la5026125
Surface-immobilized rotaxanes are of practical interest for myriad applications including molecular rotors and analytical sensing. Herein, we present a facile method for the preparation of cucurbit[8]uril (CB[8])-based rotaxanes on gold (Au) surfaces threaded onto a viologen (MV2+) axle. The surface-bound CB[8] rotaxanes were characterized by contact angle measurements and optical microscopy. Direct imaging of the rotaxanes was accomplished by attaching either azobenzene-functionalized silica (Si-azo) colloids or fluorescein-labeled dopamine that were bound to the Au surface through a supramolecular heteroternary (1:1:1) complex with CB[8]. The surface density of CB[8] rotaxanes was examined based on their detection of dopamine. The calculated surface density is 4.8 × 1013 molecules·cm–2, which is only slightly lower than the theoretical value of 5.0 × 1013 molecules·cm–2. Surface-functionalized rotaxanes can be reversibly switched using external stimuli to bind electron-rich second guests for CB[8], including both small molecules such as dopamine and appropriately-functionalized colloidal particles. Such controlled reversibility gives rise to potential applications including selective sensing or reusable templates for preparing well-defined colloidal arrays. The formation of the surface-bound rotaxane structure is critical for successfully anchoring CB[8] host molecules onto Au substrates, yielding an interlocked architecture and preventing the dissociation of binary host–guest complex MV2+⊂CB[8]. The MV2+⊂CB[8] rotaxane structure thus effectively maintains the material density on the Au surface and dramatically enhances the stability of the functional surface.
Co-reporter:Guanglu Wu, Magdalena Olesińska, Yuchao Wu, Dijana Matak-Vinkovic, and Oren A. Scherman
Journal of the American Chemical Society March 1, 2017 Volume 139(Issue 8) pp:3202-3202
Publication Date(Web):February 15, 2017
DOI:10.1021/jacs.6b13074
A 1:1 binding stoichiometry of a host–guest complex need not consist of a single host and guest. Diarylviologens containing electron-donating substituents complexed with cucurbit[8]uril (CB[8]) in a 1:1 stoichiometry exhibit abnormally large binding enthalpies compared to typical enthalpy changes observed for 1:1 binary complexes. Here, several CB[8]-mediated host–guest complexes, which were previously reported as 1:1 binary complexes, are verified to be 2:2 quaternary complexes by a combination of isothermal titration calorimetry, 1H, NOESY, and ROESY NMR, and ion mobility mass spectrometry, clearly indicating a binding motif of two partially overlapping diarylviologens held in place with two CB[8] molecules. Formation of 2:2 quaternary complexes is favored by electron-donating substituents, while electron-withdrawing substituents typically result in 1:1 binary complexes. The stacking of two highly conjugated diarylviologens in one quaternary motif affords the complexes enhanced conductance when considered as a single-molecular conductor. Moreover, an additional conducting signal previously observed for this “supramolecular” conductor can be readily understood with our 2:2 complexation model, corresponding to a parallel conductance pathway. Therefore, a 2:2 quaternary complex model grants a greater understanding of such supramolecular complexes, enabling the design of engineered, hierarchical structures and functional materials.
Co-reporter:Anna M. Cieślak;Emma-Rose Janeček;Kamil Sokołowski;Tomasz Ratajczyk;Michał K. Leszczyński;Janusz Lewiński
Nanoscale (2009-Present) 2017 vol. 9(Issue 42) pp:16128-16132
Publication Date(Web):2017/11/02
DOI:10.1039/C7NR03095A
Herein, we show how the inherent light-induced redox properties of semiconducting nanocrystals (NCs) can be utilized for the photo-driven reversible modulation of dynamic supramolecular systems formed at their interfaces that, on their own, do not respond to light. This was achieved by the unprecedented combination of photoactive zinc oxide NCs (ZnO NCs) with a host–guest chemistry of cucurbit[8]uril (CB[8]) providing a route to the semiconductor-assisted light modulation of supramolecular assemblies (SALSA), here mediated by the photo-generation of viologen radical cations (MV˙+) at the NC corona and their further dimerization enhanced by CB[8] macrocycles. The reported SALSA strategy was successfully applied for light-controlled reversible assembly processes at NC interfaces enabling light-triggered release of guest molecules from surface confined discrete CB[8] host–guest complexes.
Co-reporter:Bart de Nijs;Marlous Kamp;Istvan Szabó;Steven J. Barrow;Felix Benz;Guanglu Wu;Cloudy Carnegie;Rohit Chikkaraddy;Wenting Wang;William M. Deacon;Edina Rosta;Jeremy J. Baumberg
Faraday Discussions 2017 (Volume 205) pp:505-515
Publication Date(Web):2017/11/30
DOI:10.1039/C7FD00147A
Rigid gap nano-aggregates of Au nanoparticles formed using cucurbit[n]uril (CB[n]) molecules are used to investigate the competitive binding of ethanol and methanol in an aqueous environment. We show it is possible to detect as little as 0.1% methanol in water and a ten times higher affinity to methanol over ethanol, making this a useful technology for quality control in alcohol production. We demonstrate strong interaction effects in the SERS peaks, which we demonstrate are likely from the hydrogen bonding of water complexes in the vicinity of the CB[n]s.
Co-reporter:Cindy Soo Yun Tan;Gillie Agmon;Ji Liu;Dominique Hoogland;Emma-Rose Janeček;Eric A. Appel
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 35) pp:5336-5343
Publication Date(Web):2017/09/12
DOI:10.1039/C7PY00574A
Polymeric materials based on reversible non-covalent associations possess diverse mechanical behaviour, responsiveness to external stimuli and self-healing properties. Unlike covalently-bonded polymeric materials, whose properties are conventionally engineered through the polymer structure alone, the mechanical performance of a supramolecular material can be designed via two motifs: the polymer architecture (e.g., polymer molecular weight or structure) and the physical crosslinks (e.g., thermodynamics or kinetics of binding) between polymers. Here, we demonstrate the preparation of aqueous-based supramolecular polymeric materials utilising cucurbit[8]uril (CB[8]) crosslinking of multivalent polymers of varying molecular weights. By exploiting three kinetically distinct supramolecular motifs, we show that it is possible to relate the contributions of polymer architecture and dynamic crosslinking to the ultimate mechanical properties of the materials. These studies improve our understanding of the challenging relationships between design of supramolecular polymeric materials and their complex viscoelastic behaviour as well as relaxation dynamics.
Co-reporter:Ji Liu;Cindy Soo Yun Tan;Ziyi Yu;Nan Li;Chris Abell
Advanced Materials 2017 Volume 29(Issue 22) pp:
Publication Date(Web):2017/06/01
DOI:10.1002/adma.201605325
Recent progress on highly tough and stretchable polymer networks has highlighted the potential of wearable electronic devices and structural biomaterials such as cartilage. For some given applications, a combination of desirable mechanical properties including stiffness, strength, toughness, damping, fatigue resistance, and self-healing ability is required. However, integrating such a rigorous set of requirements imposes substantial complexity and difficulty in the design and fabrication of these polymer networks, and has rarely been realized. Here, we describe the construction of supramolecular polymer networks through an in situ copolymerization of acrylamide and functional monomers, which are dynamically complexed with the host molecule cucurbit[8]uril (CB[8]). High molecular weight, thus sufficient chain entanglement, combined with a small-amount dynamic CB[8]-mediated non-covalent crosslinking (2.5 mol%), yields extremely stretchable and tough supramolecular polymer networks, exhibiting remarkable self-healing capability at room temperature. These supramolecular polymer networks can be stretched more than 100× their original length and are able to lift objects 2000× their weight. The reversible association/dissociation of the host–guest complexes bestows the networks with remarkable energy dissipation capability, but also facile complete self-healing at room temperature. In addition to their outstanding mechanical properties, the networks are ionically conductive and transparent. The CB[8]-based supramolecular networks are synthetically accessible in large scale and exhibit outstanding mechanical properties. They could readily lead to the promising use as wearable and self-healable electronic devices, sensors and structural biomaterials.
Co-reporter:Dr. Aniello Palma;Markus Artelsmair;Dr. Guanglu Wu;Dr. Xiaoyong Lu;Dr. Steven J. Barrow;Najib Uddin;Dr. Edina Rosta; Eric Masson; Oren A. Scherman
Angewandte Chemie 2017 Volume 129(Issue 49) pp:15894-15898
Publication Date(Web):2017/12/04
DOI:10.1002/ange.201706487
AbstractThe ability to mimic the activity of natural enzymes using supramolecular constructs (artificial enzymes) is a vibrant scientific research field. Herein, we demonstrate that cucurbit[7]uril (CB[7]) can catalyse Diels–Alder reactions for a number of substituted and unreactive N-allyl-2-furfurylamines under biomimetic conditions, without the need for protecting groups, yielding powerful synthons in previously unreported mild conditions. CB[7] rearranges the substrate in a highly reactive conformation and shields it from the aqueous environment, thereby mimicking the mode of action of a natural Diels–Alderase. These findings can be directly applied to the phenomenon of product inhibition observed in natural Diels–Alderase enzymes, and pave the way toward the development of novel, supramolecular-based green catalysts.
Co-reporter:Dr. Aniello Palma;Markus Artelsmair;Dr. Guanglu Wu;Dr. Xiaoyong Lu;Dr. Steven J. Barrow;Najib Uddin;Dr. Edina Rosta; Eric Masson; Oren A. Scherman
Angewandte Chemie International Edition 2017 Volume 56(Issue 49) pp:15688-15692
Publication Date(Web):2017/12/04
DOI:10.1002/anie.201706487
AbstractThe ability to mimic the activity of natural enzymes using supramolecular constructs (artificial enzymes) is a vibrant scientific research field. Herein, we demonstrate that cucurbit[7]uril (CB[7]) can catalyse Diels–Alder reactions for a number of substituted and unreactive N-allyl-2-furfurylamines under biomimetic conditions, without the need for protecting groups, yielding powerful synthons in previously unreported mild conditions. CB[7] rearranges the substrate in a highly reactive conformation and shields it from the aqueous environment, thereby mimicking the mode of action of a natural Diels–Alderase. These findings can be directly applied to the phenomenon of product inhibition observed in natural Diels–Alderase enzymes, and pave the way toward the development of novel, supramolecular-based green catalysts.
Co-reporter:Guanglu Wu;Darshil U. Shah;Emma-Rose Janeček
Wood Science and Technology 2017 Volume 51( Issue 6) pp:1277-1290
Publication Date(Web):07 July 2017
DOI:10.1007/s00226-017-0933-6
Lumen impregnation, unlike most other wood modification methods, is typically assessed by the pore-filling ratio (PFR) (i.e. the fraction of luminal porosity filled) rather than by weight percentage gain (WPG). During lumen impregnation, the impregnants act on the voids in the wood rather than on the solid mass (e.g. cell walls), but the PFR cannot be measured as conveniently as the WPG during processing. Here, it is demonstrated how the PFR can be calculated directly from the WPG if the bulk density of the untreated wood is known. The relationship between the WPG and bulk density was examined experimentally by applying a pressured impregnation on knot-free specimens from Sitka spruce with a liquid mixture of methacrylate monomers. Based on the validated model, it was possible to further study the effect of different process-related parameters, such as hydraulic pressure, on lumen impregnation. Skeletal density is another key parameter in this model, which directly reflects the amount of inaccessible pores and closed lumens, and can be independently determined by helium pycnometry. The permeability can be qualitatively evaluated by PFR as well as skeletal density. For instance, poor permeability of knotty wood, due to the large extractives content around knots, was reflected by a lower skeletal density and inefficient lumen impregnation (low PFR). Although this model was examined on a laboratory scale, it provides guidance on the precise effect of different parameters on lumen impregnation, thereby improving the fundamental understanding of and enabling better control over the modification of wood by impregnation.
Co-reporter:Michael H. Ramage, Henry Burridge, Marta Busse-Wicher, George Fereday, Thomas Reynolds, Darshil U. Shah, Guanglu Wu, Li Yu, Patrick Fleming, Danielle Densley-Tingley, Julian Allwood, Paul Dupree, P.F. Linden, Oren Scherman
Renewable and Sustainable Energy Reviews 2017 Volume 68, Part 1(Volume 68, Part 1) pp:
Publication Date(Web):1 February 2017
DOI:10.1016/j.rser.2016.09.107
Trees, and their derivative products, have been used by societies around the world for thousands of years. Contemporary construction of tall buildings from timber, in whole or in part, suggests a growing interest in the potential for building with wood at a scale not previously attainable. As wood is the only significant building material that is grown, we have a natural inclination that building in wood is good for the environment. But under what conditions is this really the case? The environmental benefits of using timber are not straightforward; although it is a natural product, a large amount of energy is used to dry and process it. Much of this can come from the biomass of the tree itself, but that requires investment in plant, which is not always possible in an industry that is widely distributed among many small producers. And what should we build with wood? Are skyscrapers in timber a good use of this natural resource, or are there other aspects of civil and structural engineering, or large-scale infrastructure, that would be a better use of wood? Here, we consider a holistic picture ranging in scale from the science of the cell wall to the engineering and global policies that could maximise forestry and timber construction as a boon to both people and the planet.
Co-reporter:Chenyan Liu;Guolei Xiang;Yuchao Wu;Steven J. Barrow;Matthew J. Rowland;David E. Clarke;Guanglu Wu
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 4) pp:795-795
Publication Date(Web):2017/01/24
DOI:10.1039/C6PY90193J
Correction for ‘Hybrid organic–inorganic supramolecular hydrogel reinforced with CePO4 nanowires’ by Chenyan Liu et al., Polym. Chem., 2016, 7, 6485–6489.
Co-reporter:Alexander S. Groombridge;Aniello Palma;Richard M. Parker;Chris Abell
Chemical Science (2010-Present) 2017 vol. 8(Issue 2) pp:1350-1355
Publication Date(Web):2017/01/30
DOI:10.1039/C6SC04103E
The self-assembly of a stimuli-responsive aqueous supramolecular hyperbranched polymer from small molecules is reported. This system is composed of ditopic and tritopic guest-functionalised molecules that are able to form heteroternary supramolecular complexes with the macrocyclic host cucurbit[8]uril (CB[8]). We demonstrate that the supramolecular hyperbranched polymer formed is responsive to both photo- and chemical stimuli, exhibiting reversibility. Furthermore, this system is shown to assemble at liquid–liquid interfaces, which upon gelation, is observable on the micrometre scale. This self-healing supramolecular network can act as a soft matter barrier for aqueous microdroplets, inhibiting their coalescence.
Co-reporter:Emma-Rose Janeček;Zarah Walsh-Korb;Ilaria Bargigia
Wood Science and Technology 2017 Volume 51( Issue 2) pp:227-242
Publication Date(Web):2017 March
DOI:10.1007/s00226-016-0882-5
Time-resolved diffuse optical spectroscopy (TRS) was investigated as a nondestructive method to characterize the post-impregnation distribution of methacrylate monomers within spruce (Picea abies). TRS was also used to monitor the flow of methacrylate monomers in situ, within spruce, during impregnation with both spatial and temporal resolution. The data were compared to fluid flow models developed by Darcy and Bramhall demonstrating that neither of these models were able to accurately describe the experimental results, highlighting the need for development of new models. Nondestructive characterization by TRS did not require staining of the monomer treatment solution, multivariate analysis or complex sample pre-treatment, thus highlighting the facile applicability of this technique.
Co-reporter:Ji Liu, Yang Lan, Ziyi Yu, Cindy S.Y. Tan, Richard M. ParkerChris Abell, Oren A. Scherman
Accounts of Chemical Research 2017 Volume 50(Issue 2) pp:
Publication Date(Web):January 11, 2017
DOI:10.1021/acs.accounts.6b00429
ConspectusMicroencapsulation is a fundamental concept behind a wide range of daily applications ranging from paints, adhesives, and pesticides to targeted drug delivery, transport of vaccines, and self-healing concretes. The beauty of microfluidics to generate microcapsules arises from the capability of fabricating monodisperse and micrometer-scale droplets, which can lead to microcapsules/particles with fine-tuned control over size, shape, and hierarchical structure, as well as high reproducibility, efficient material usage, and high-throughput manipulation. The introduction of supramolecular chemistry, such as host–guest interactions, endows the resultant microcapsules with stimuli-responsiveness and self-adjusting capabilities, and facilitates hierarchical microstructures with tunable stability and porosity, leading to the maturity of current microencapsulation industry.Supramolecular architectures and materials have attracted immense attention over the past decade, as they open the possibility to obtain a large variety of aesthetically pleasing structures, with myriad applications in biomedicine, energy, sensing, catalysis, and biomimicry, on account of the inherent reversible and adaptive nature of supramolecular interactions. As a subset of supramolecular interactions, host–guest molecular recognition involves the formation of inclusion complexes between two or more moieties, with specific three-dimensional structures and spatial arrangements, in a highly controllable and cooperative manner. Such highly selective, strong yet dynamic interactions could be exploited as an alternative methodology for programmable and controllable engineering of supramolecular architectures and materials, exploiting reversible interactions between complementary components. Through the engineering of molecular structures, assemblies can be readily functionalized based on host–guest interactions, with desirable physicochemical characteristics.In this Account, we summarize the current state of development in the field of monodisperse supramolecular microcapsules, fabricated through the integration of traditional microfluidic techniques and interfacial host–guest chemistry, specifically cucurbit[n]uril (CB[n])-mediated host–guest interactions. Three different strategies, colloidal particle-driven assembly, interfacial condensation-driven assembly and electrostatic interaction-driven assembly, are classified and discussed in detail, presenting the methodology involved in each microcapsule formation process. We highlight the state-of-the-art in design and control over structural complexity with desirable functionality, as well as promising applications, such as cargo delivery stemming from the assembled microcapsules. On account of its dynamic nature, the CB[n]-mediated host–guest complexation has demonstrated efficient response toward various external stimuli such as UV light, pH change, redox chemistry, and competitive guests. Herein, we also demonstrate different microcapsule modalities, which are engineered with CB[n] host–guest chemistry and also can be disrupted with the aid of external stimuli, for triggered release of payloads. In addition to the overview of recent achievements and current limitations of these microcapsules, we finally summarize several perspectives on tunable cargo loading and triggered release, directions, and challenges for this technology, as well as possible strategies for further improvement, which will lead to substainitial progress of host–guest chemistry in supramolecular architectures and materials.
Co-reporter:Silvia Sonzini;Helen F. Stanyon
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 2) pp:1458-1465
Publication Date(Web):2017/01/04
DOI:10.1039/C6CP06765D
Amyloid β is one of the peptides involved in the onset of Alzheimer's disease, yet the structure of the toxic species and its underlying mechanism remain elusive on account of the dynamic nature of the Aβ oligomerisation process. While it has been reported that incubation of Amyloid β (1–42) sequences (Aβ42) lead to formation of aggregates that vary in morphology and toxicity, we demonstrate that addition of a discrete macrocyclic host molecule, cucurbit[8]uril (CB[8]), substantially reduces toxicity in the neuronal cell line SH-SY5Y. The macrocycle preferentially targets Phe residues in Aβ42 complexing them in a 2 : 1 fashion in neighboring peptide strands. A small but significant structural ‘switch’ occurs, which induces an increased aggregation rate, suggesting a different cell-uptake mechanism for Aβ42 in the presence of CB[8]. Dramatically increasing the rate of Aβ42 aggregation with CB[8] bypasses the toxic, oligomeric state offering an alternative approach to counter Alzheimer's disease.
Co-reporter:Jade A. McCune;Edina Rosta
Organic & Biomolecular Chemistry 2017 vol. 15(Issue 4) pp:998-1005
Publication Date(Web):2017/01/25
DOI:10.1039/C6OB02594C
The functionalisation of cucurbit[n]uril macrocycles carried out through an oxidative approach in water using ammonium persulfate was studied. Through complexation with a doubly-charged bisimidazolium guest we were able to detect, distinguish and quantify the presence of each CB[n]-(OH)x (where 1 ≤ x ≤ 2n) derivative for the first time. The impact of oxidation on each CB[n] (n = 6–8) was studied individually, as well as in the presence of other competing CB[n] species. We were able to understand the reactivity of the parent CB[n] alongside its hydroxylated derivatives, CB[n]-(OH)x, and show that the oxidation of CB[n] through a free-radical approach cannot result in stoichiometric hydroxylation despite previous literature reports by Bardelang, Ouari and co-workers, J. Am. Chem. Soc., 2015, 137, 10238. Furthermore, an in-depth study on hydroxylation of CB[7] was conducted. Through DFT calculations we were able to show that the second hydroxy substituent is preferentially located on the same glycoluril unit. Moreover, through optimisation of the reaction conditions we were able to access a protocol for controlled oxidation to yield a chemically monofunctional CB[7] derivative.
Co-reporter:Jesús del Barrio; Seán T. J. Ryan; Pablo G. Jambrina; Edina Rosta
Journal of the American Chemical Society 2016 Volume 138(Issue 18) pp:5745-5748
Publication Date(Web):February 14, 2016
DOI:10.1021/jacs.5b11642
Cucurbit[8]uril (CB[8])-mediated complexation of a dicationic azobenzene in water allows for the light-controlled encapsulation of a variety of second guest compounds, including amino acids, dyes, and fragrance molecules. Such controlled guest sequestration inside the cavity of CB[8] enables the regulation of the thermally induced phase transition of poly(N-isopropylacrylamide)—which is not photosensitive—thus demonstrating the robustness and relevancy of the light-regulated CB[8] complexation.
Co-reporter:Chi Hu, Kevin R. West and Oren A. Scherman
Nanoscale 2016 vol. 8(Issue 15) pp:7840-7844
Publication Date(Web):11 Mar 2016
DOI:10.1039/C6NR01016D
The fabrication, characterisation and controlled cargo release of hollow mesoporous raspberry-like colloids (HMRCs), which are assembled by utilising host–guest complexation of cucurbit[8]uril (CB[8]) are described. CB[8] is employed as a supramolecular linker to ‘stick’ the viologen functionalised paramagnetic iron oxide nanoparticles onto an azobenzene functionalised hollow mesoporous silica core. The formed HMRCs are photoresponsive and can be reversibly disassembled upon light irradiation, endowing them with an ability to release loaded cargo under photocontrol. While the assembled HMRCs retain cargo inside their cavity, disassembled particles with their iron oxide nanoparticle ‘caps’ removed will release the loaded cargo through the mesoporous shell of the hollow silica colloids. A model system using a boronic acid derivative as the cargo in the HMRCs and Alizarin Red salt as a sensor for the released boronic acid is demonstrated.
Co-reporter:Ziyi Yu, Yu Zheng, Richard M. Parker, Yang Lan, Yuchao Wu, Roger J. Coulston, Jing Zhang, Oren A. Scherman, and Chris Abell
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 13) pp:8811
Publication Date(Web):March 16, 2016
DOI:10.1021/acsami.6b00661
Bottom-up hierarchical assembly has emerged as an elaborate and energy-efficient strategy for the fabrication of smart materials. Herein, we present a hierarchical assembly process, whereby linear amphiphilic block copolymers are self-assembled into micelles, which in turn are accommodated at the interface of microfluidic droplets via cucurbit[8]uril-mediated host–guest chemistry to form supramolecular microcapsules. The monodisperse microcapsules can be used for simultaneous carriage of both organic (Nile Red) and aqueous-soluble (fluorescein isothiocyanate-dextran) cargo. Furthermore, the well-defined compartmentalized structure benefits from the dynamic nature of the supramolecular interaction and offers synergistic delivery of cargos with triggered release or through photocontrolled porosity. This demonstration of premeditated hierarchical assembly, where interactions from the molecular to microscale are designed, illustrates the power of this route toward accessing the next generation of functional materials and encapsulation strategies.Keywords: cucurbit[8]uril; dual cargo delivery; hierarchical assembly; microcapsules; microfluidic droplets
Co-reporter:R. J. Gubeli, S. Sonzini, A. Podmore, P. Ravn, O. A. Scherman and C. F. van der Walle
Chemical Communications 2016 vol. 52(Issue 22) pp:4235-4238
Publication Date(Web):22 Feb 2016
DOI:10.1039/C6CC00405A
The combination of potent chemical moieties with biologically active proteins is key to some of today's most innovative therapeutic drugs. In order to obviate any chemical modification of the proteins, we present a novel and powerful strategy for the selective conjugation of recombinant protein domains with synthetically derived peptides via a cucurbit[8]uril host–guest chemistry approach.
Co-reporter:Ji Liu;Cindy Soo Yun Tan;Yang Lan
Macromolecular Chemistry and Physics 2016 Volume 217( Issue 3) pp:319-332
Publication Date(Web):
DOI:10.1002/macp.201500295
Co-reporter:Daniel O. Sigle; Setu Kasera; Lars O. Herrmann; Aniello Palma; Bart de Nijs; Felix Benz; Sumeet Mahajan; Jeremy J. Baumberg
The Journal of Physical Chemistry Letters 2016 Volume 7(Issue 4) pp:704-710
Publication Date(Web):January 14, 2016
DOI:10.1021/acs.jpclett.5b02535
In recent years, single-molecule sensitivity achievable by surface-enhanced Raman spectroscopy (SERS) has been widely reported. We use this to investigate supramolecular host–guest chemistry with the macrocyclic host cucurbit[7]uril, on a few-to-single-molecule level. A nanogap geometry, comprising individual gold nanoparticles on a planar gold surface spaced by a single layer of molecules, gives intense SERS signals. Plasmonic coupling between the particle and the surface leads to strongly enhanced optical fields in the gap between them, with single-molecule sensitivity established using a modification of the well-known bianalyte method. Changes in the Raman modes of the host molecule are observed when single guests included inside its cavity internally stretch it. Anisotropic intermolecular interactions with the guest are found which show additional distinct features in the Raman modes of the host molecule.
Co-reporter:Samuel T. Jones, Zarah Walsh-Korb, Steven J. Barrow, Sarah L. Henderson, Jesús del Barrio, and Oren A. Scherman
ACS Nano 2016 Volume 10(Issue 3) pp:3158
Publication Date(Web):January 20, 2016
DOI:10.1021/acsnano.5b04083
Thermoresponsive materials are generating significant interest on account of the sharp and tunable temperature deswelling transition of the polymer chain. Such materials have shown promise in drug delivery devices, sensing systems, and self-assembly. Incorporation of nanoparticles (NPs), typically through covalent attachment of the polymer chains to the NP surface, can add additional functionality and tunability to such hybrid materials. The versatility of these thermoresponsive polymer/nanoparticle materials has been shown previously; however, significant and important differences exist in the published literature between virtually identical materials. Here we use poly(N-isopropylacrylamide) (PNIPAm)-AuNPs as a model system to understand the aggregation behavior of thermoresponsive polymer-coated nanoparticles in pure water, made by either grafting-to or grafting-from methods. We show that, contrary to popular belief, the aggregation of PNIPAm-coated AuNPs, and likely other such materials, relies on the size and concentration of unbound “free” PNIPAm in solution. It is this unbound polymer that also leads to an increase in solution turbidity, a characteristic that is typically used to prove nanoparticle aggregation. The size of PNIPAm used to coat the AuNPs, as well as the concentration of the resultant polymer–AuNP composites, is shown to have little effect on aggregation. Without free PNIPAm, contraction of the polymer corona in response to increasing temperature is observed, instead of nanoparticle aggregation, and is accompanied by no change in solution turbidity or color. We develop an alternative method for removing all traces of excess free polymer and develop an approach for analyzing the aggregation behavior of such materials, which truly allows for heat-triggered aggregation to be studied.Keywords: aggregate; aggregation; gold; LCST; N-isopropylacrylamide; nanoparticle; NIPAm
Co-reporter:Steven J. Barrow, Setu Kasera, Matthew J. Rowland, Jesús del Barrio, and Oren A. Scherman
Chemical Reviews 2015 Volume 115(Issue 22) pp:12320
Publication Date(Web):November 13, 2015
DOI:10.1021/acs.chemrev.5b00341
Co-reporter:Chi Hu;Yang Lan;Kevin R. West
Advanced Materials 2015 Volume 27( Issue 48) pp:7957-7962
Publication Date(Web):
DOI:10.1002/adma.201503844
Co-reporter:Chuang Li;Matthew J. Rowl;Yu Shao;Tianyang Cao;Chun Chen;Haoyang Jia;Xu Zhou;Zhongqiang Yang;Dongsheng Liu
Advanced Materials 2015 Volume 27( Issue 21) pp:3298-3304
Publication Date(Web):
DOI:10.1002/adma.201501102
Co-reporter:Seán T. J. Ryan; Ryan M. Young; James J. Henkelis; Nema Hafezi; Nicolaas A. Vermeulen; Andreas Hennig; Edward J. Dale; Yilei Wu; Matthew D. Krzyaniak; Athan Fox; Werner M. Nau; Michael R. Wasielewski; J. Fraser Stoddart
Journal of the American Chemical Society 2015 Volume 137(Issue 48) pp:15299-15307
Publication Date(Web):November 9, 2015
DOI:10.1021/jacs.5b10329
Artificial photosynthetic systems for solar energy conversion exploit both covalent and supramolecular chemistry to produce favorable arrangements of light-harvesting and redox-active chromophores in space. An understanding of the interplay between key processes for photosynthesis, namely light-harvesting, energy transfer, and photoinduced charge separation and the design of novel, self-assembling components capable of these processes are imperative for the realization of multifunctional integrated systems. We report our investigations on the potential of extended tetracationic cyclophane/perylene diimide systems as components for artificial photosynthetic applications. We show how the selection of appropriate heterocycles, as extending units, allows for tuning of the electron accumulation and photophysical properties of the extended tetracationic cyclophanes. Spectroscopic techniques confirm energy transfer between the extended tetracationic cyclophanes and perylene diimide is ultrafast and quantitative, while the heterocycle specifically influences the energy transfer related parameters and the acceptor excited state.
Co-reporter:Ziyi Yu, Jing Zhang, Roger J. Coulston, Richard M. Parker, Frank Biedermann, Xin Liu, Oren A. Scherman and Chris Abell
Chemical Science 2015 vol. 6(Issue 8) pp:4929-4933
Publication Date(Web):11 Jun 2015
DOI:10.1039/C5SC01440A
Host–guest assembly in droplet-based microfluidics opens a new avenue for fabricating supramolecular hydrogel microcapsules with high monodispersity and controlled functionality. In this paper, we demonstrate a single emulsion microdroplet platform to prepare microcapsules with supramolecular hydrogel skins from host molecule cucurbit[8]uril and guest polymer anthracene-functionalized hydroxyethyl cellulose. In contrast to construction of microcapsules from a droplet-in-droplet double emulsion, here the electrostatic attraction between charged polymer and surfactant facilitates formation of defined supramolecular hydrogel skins in a single emulsion. Furthermore, by taking advantage of dynamic interactions and the tunable cross-linked supramolecular hydrogel network, it is possible to prepare microcapsules with triggered and UV-controlled molecular permeability. These could be potentially used in a delivery system for e.g. agrochemicals, nutraceuticals or cosmetics.
Co-reporter:Chi Hu, Feng Tian, Yu Zheng, Cindy Soo Yun Tan, Kevin R. West and Oren A. Scherman
Chemical Science 2015 vol. 6(Issue 9) pp:5303-5310
Publication Date(Web):06 Jul 2015
DOI:10.1039/C5SC01496D
In situ modification of surfaces with thin layers of polymers is of growing interest as adjustment of surface properties can be made on demand. We present herein a supramolecular ‘grafting to’ polymer brush via the recognition of surface-bound cucurbit[8]uril (CB[8]) rotaxanes towards end-functionalised polyethylene glycol (PEG). This dynamic supramolecular method represents advantages over traditional approaches, which employ covalent bond formation in the ‘grafting to’ process. Brush properties can be easily modified post-preparation by exchanging the polymers with small molecules in a controlled, reversible manner. Including both redox- and light-responsive guests in a single rotaxane entity, the CB[8]-mediated preparation of the polymer brush offers unique opportunities to switch the brush composition efficiently. While the PEG brushes are well hydrated in a good solvent (water) and stretch away from the surface, they collapse in a poor solvent (toluene), leading to the formation of a dense layer on the surface. This collapsed conformation protects the heteroternary complexes of CB[8]-rotaxane from dissociation and maintains the attachment of polymers on the surface.
Co-reporter:Anna Andreou, Michal Leskes, Pablo G. Jambrina, Gary J. Tustin, Clare P. Grey, Edina Rosta and Oren A. Scherman
Chemical Science 2015 vol. 6(Issue 11) pp:6262-6269
Publication Date(Web):06 Aug 2015
DOI:10.1039/C4SC02729A
The hydroboration 1,3- and 1,4-cyclic dienes has been systematically investigated. The behavior of such dienes towards mono and dihydroboration was monitored directly by 11B NMR to identify the actual boron species formed, as opposed to the most common analysis of the resultant oxidation products. Quantitative dihydroboration was achieved for the full range of cyclic dienes investigated including dienes, which were previously reported to be resistant to dihydroboration, leading to the formation of new boron-containing polymeric materials. The conditions favoring dihydroboration are reported as well as full characterisation of the materials. Furthermore, a hydroboration cascade mechanism is proposed for the formation of such boron-containing polymers, supported by both experimental and theoretical data.
Co-reporter:Yuchao Wu, Yang Lan, Ji Liu and Oren A. Scherman
Nanoscale 2015 vol. 7(Issue 32) pp:13416-13419
Publication Date(Web):24 Jun 2015
DOI:10.1039/C5NR03647J
Polymeric nanocomposites were prepared by using cucurbit[7]uril as a ‘supramolecular anchor’, as well as stabilising ligand to immobilise catalytic transition-metal nanoparticles on the surface of methyl viologen-bearing polymeric colloids. This facile and spontaneous supramolecular approach allows for control over size, morphology and composition of the nanocomposites. The small metallic nanoparticles impart the nanocomposites with great potential in catalysis.
Co-reporter:Chi Hu, Yu Zheng, Ziyi Yu, Chris Abell and Oren A. Scherman
Chemical Communications 2015 vol. 51(Issue 23) pp:4858-4860
Publication Date(Web):11 Feb 2015
DOI:10.1039/C5CC00121H
The fabrication, characterisation and controlled burst release of naphthol-functionalised micellar (NFM) nanostructures, which were grafted onto gold surfaces through cucurbit[8]uril (CB[8]) mediated host–guest interactions are described. NFMs undergo a facile change in morphology from micelles to diblock copolymers in direct response to exposure to organic solvents, including tetrahydrofuran (THF), toluene and chloroform. This induced transition in conformation lends itself to potential applications including nanocarriers for triggered burst-release of guest molecules. Nile Red was investigated as a NFM encapsulated model hydrophobic cargo inside the surface-attached micelles, which could be fully released upon exposure to THF as measured by both atomic force microscopy and UV/vis spectroscopy.
Co-reporter:Cindy S. Y. Tan, Jesús del Barrio, Ji Liu and Oren A. Scherman
Polymer Chemistry 2015 vol. 6(Issue 44) pp:7652-7657
Publication Date(Web):11 Aug 2015
DOI:10.1039/C5PY01115A
We describe a low-mass fraction (≤0.75 wt%) supramolecular polymer network as an aqueous photo-rheological fluid (PRF) whose rheological properties can be easily modulated via light irradiation. This supramolecular polymer network is formed via CB[8]-assisted host–guest interactions between naphthyl-functionalised hydroxyethyl cellulose (HEC-Np), methyl viologen containing styrene copolymer (PSTMV), cucurbit[8]uril (CB[8]) and a photoisomerisable azobenzene imidazolium (AzoIm) derivative. This cellulose-based PRF can undergo a UV-triggered rapid transition from a highly viscous and rigid gel into a Newtonian-like fluid, with a decrease in zero-shear viscosity of over two orders of magnitude. Moreover, the rate of viscosity reduction of these PRFs can be tuned based on the mixture composition and duration of photoirradiation.
Co-reporter:Paul E. Williams, Samuel T. Jones, Zarah Walsh, Eric A. Appel, Enass K. Abo-Hamed, and Oren A. Scherman
ACS Macro Letters 2015 Volume 4(Issue 2) pp:255
Publication Date(Web):February 3, 2015
DOI:10.1021/mz500645c
The direct covalent attachment of conducting polymers (CP) to nanoparticles (NP) to form CP-NP nanohybrids is of great interest for optoelectronic device applications. Hybrids formed by covalently anchoring CP to NP, rather than traditional blending or bilayer approaches, is highly desirable. CP-NP nanohybrids have increased interfacial surface area between the two components, facilitating rapid exciton diffusion at the p–n heterojunction. These materials take advantage of the facile solution processability, lightweight characteristics, flexibility, and mechanical strength associated with CPs, and the broad spectral absorption, photostability, and high charge carrier mobility of NPs. We demonstrate the ability to polymerize a hole transporting (HT) polymer utilizing reversible-addition–fragmentation chain transfer (RAFT) polymerization and its subsequent rapid aminolysis to yield a thiol-terminated HT polymer. Subsequent facile attachment to gold (Au) and silver (Ag) NPs and cadmium selenide (CdSe) quantum dots (QDs), to form a number of CP–NP systems is demonstrated and characterized. CP–NP nanohybrids show broad spectral absorptions ranging from UV through visible to the near IR, and their facile synthesis and purification could allow for large scale industrial applications.
Co-reporter:Silvia Sonzini, Samuel T. Jones, Zarah Walsh and Oren A. Scherman
Analyst 2015 vol. 140(Issue 8) pp:2735-2740
Publication Date(Web):29 Jan 2015
DOI:10.1039/C4AN02278E
Peptide aggregation and fibre formation are one of the major underlying causes of several neurodegenerative disorders such as Alzheimer's disease. During the past decades the characterisation of these fibres has been widely studied in an attempt to further understand the nature of the related diseases and in an effort to develop treatments. Transmission electron microscopy (TEM) is one of the most commonly used techniques to identify these fibres, but requires the use of a radioactive staining agent. The procedure we report overcomes this drawback through simple addition of a fluorinated moiety to a short Amyloid β sequence via solid phase peptide synthesis (SPPS). This method is synthetically straightforward, widely applicable to different aggregation-prone sequences and, above all, allows for stain-free TEM imaging with improved quality compared to standard imaging procedures. The presence of the fluorinated moiety does not cause major changes in the fibre structure or aggregation, but rather serves to dissipate the microscope's electron beam, thus allowing for high contrast and straightforward imaging by TEM.
Co-reporter:Dr. Lifei Zheng;Silvia Sonzini;Masyitha Ambarwati;Dr. Edina Rosta;Dr. Oren A. Scherman;Dr. Andreas Herrmann
Angewandte Chemie 2015 Volume 127( Issue 44) pp:13199-13203
Publication Date(Web):
DOI:10.1002/ange.201505628
Abstract
Chiral macromolecules have been widely used as synthetic pockets to mimic natural enzymes and promote asymmetric reactions. An achiral host, cucurbit[8]uril (CB[8]), was used for an asymmetric Lewis acid catalyzed Diels–Alder reaction. We achieved a remarkable increase in enantioselectivity and a large rate acceleration in the presence of the nanoreactor by using an amino acid as the chiral source. Mechanistic and computational studies revealed that both the amino acid–Cu2+ complex and the dienophile substrate are included inside the macrocyclic host cavity, suggesting that contiguity and conformational constraints are fundamental to the catalytic process and rate enhancement. These results pave the way towards new studies on asymmetric reactions catalyzed in confined achiral cavities.
Co-reporter:Dr. Lifei Zheng;Silvia Sonzini;Masyitha Ambarwati;Dr. Edina Rosta;Dr. Oren A. Scherman;Dr. Andreas Herrmann
Angewandte Chemie International Edition 2015 Volume 54( Issue 44) pp:13007-13011
Publication Date(Web):
DOI:10.1002/anie.201505628
Abstract
Chiral macromolecules have been widely used as synthetic pockets to mimic natural enzymes and promote asymmetric reactions. An achiral host, cucurbit[8]uril (CB[8]), was used for an asymmetric Lewis acid catalyzed Diels–Alder reaction. We achieved a remarkable increase in enantioselectivity and a large rate acceleration in the presence of the nanoreactor by using an amino acid as the chiral source. Mechanistic and computational studies revealed that both the amino acid–Cu2+ complex and the dienophile substrate are included inside the macrocyclic host cavity, suggesting that contiguity and conformational constraints are fundamental to the catalytic process and rate enhancement. These results pave the way towards new studies on asymmetric reactions catalyzed in confined achiral cavities.
Co-reporter:Dr. Xuejiao Xu;Dr. Feng Tian;Dr. Xin Liu;Dr. Richard M. Parker;Dr. Yang Lan;Yuchao Wu;Dr. Ziyi Yu;Dr. Oren A. Scherman; Chris Abell
Chemistry - A European Journal 2015 Volume 21( Issue 44) pp:15516-15519
Publication Date(Web):
DOI:10.1002/chem.201503194
Abstract
We demonstrate a novel method for the formation of a library of structured colloidal assemblies by exploiting the supramolecular heteroternary host–guest interaction between cucurbit[8]uril (CB[8]) and methyl viologen- and naphthalene-functionalised particles. The approach is dependent upon compartmentalisation in microdroplets generated by a microfluidic platform. Though the distribution of colloidal particles encapsulated within each microdroplet followed a Poisson distribution, tuning the concentration of the initial colloidal particle suspensions provided some level of control over the structure of the formed colloidal assemblies. This ability to direct the assembly of complementarily-functionalised colloids through a supramolecular interaction, without the need for complex modification of the colloidal surface or external stimuli, presents an exciting new approach towards the design of structured colloidal materials with the potential to produce many challenging structures.
Co-reporter:Matthew J. Rowland, Marina Atgie, Dominique Hoogland, and Oren A. Scherman
Biomacromolecules 2015 Volume 16(Issue 8) pp:
Publication Date(Web):July 2, 2015
DOI:10.1021/acs.biomac.5b00680
Supramolecular hydrogels were fabricated by physically cross-linking phenylalanine functionalized polysaccharides with cucurbit[8]uril in water. We report a facile 2-step method of functionalization of the polysaccharides hyaluronic acid (HA), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), and guar with the dipeptide Phe-Cys. Addition of cucurbit[8]uril to the functional polysaccharides initiated physical cross-linking on account of strong 1:2 “homoternary” complexes with the pendant Phe residues. In particular, HA and CMC based soft hydrogels displayed impressive viscoelastic behavior which was characterized using rheology, demonstrating accessibility to an array of material properties which would find broad applicability in many fields.
Co-reporter:Xuejiao Xu, Eric A. Appel, Xin Liu, Richard M. Parker, Oren A. Scherman, and Chris Abell
Biomacromolecules 2015 Volume 16(Issue 9) pp:
Publication Date(Web):August 10, 2015
DOI:10.1021/acs.biomac.5b01048
Herein we describe the use of microdroplets as templates for the fabrication of uniform-sized supramolecular hydrogel beads, assembled by supramolecular cross-linking of functional biopolymers with the macrocyclic host molecule, cucurbit[8]uril (CB[8]). The microdroplets were formed containing diluted hydrogel precursors in solution, including the functional polymers and CB[8], in a microfluidic device. Subsequent evaporation of water from collected microdroplets concentrated the contents, driving the formation of the CB[8]-mediated host–guest ternary complex interactions and leading to the assembly of condensed three-dimensional polymeric scaffolds. Rehydration of the dried particles gave monodisperse hydrogel beads. Their equilibrium size was shown to be dependent on both the quantity of material loaded and the dimensions of the microfluidic flow focus. Fluorescein-labeled dextran was used to evaluate the efficacy of the hydrogel beads as a vector for controlled cargo release. Both passive, sustained release (hours) and triggered, fast release (minutes) of the FITC-dextran was observed, with the rate of sustained release dependent on the formulation. The kinetics of release was fitted to the Ritger-Peppas controlled release equation and shown to follow an anomalous (non-Fickian) transport mechanism.
Co-reporter:Paul E. Williams;Eric A. Appel;Samuel T. Jones;Jesús Del Barrio;Yang Lan
Journal of Polymer Science Part A: Polymer Chemistry 2015 Volume 53( Issue 7) pp:842-845
Publication Date(Web):
DOI:10.1002/pola.27517
Co-reporter:Hui Yang, Bin Yuan, and Xi Zhang , Oren A. Scherman
Accounts of Chemical Research 2014 Volume 47(Issue 7) pp:2106-2115
Publication Date(Web):April 25, 2014
DOI:10.1021/ar500105t
In this Account, we will summarize some recent progress on multifunctional stimuli-responsive biointerfaces and biosurfaces fabricated by cyclodextrin- or cucurbituril-based host–guest chemistry and highlight their potential applications including drug delivery, bioelectrocatalysis, and reversible adsorption and resistance of peptides, proteins, and cells. In addition, these biointerfaces and biosurfaces demonstrate efficient response toward various external stimuli, such as UV light, pH, redox chemistry, and competitive guests. All of these external stimuli can aid in mimicking the biological stimuli evident in complex biological environments. We begin by reviewing the current state of stimuli-responsive supramolecular assemblies formed by host–guest interactions, discussing how to transfer host–guest chemistry from solution onto surfaces required for fabricating multifunctional biosurfaces and biointerfaces. Then, we present different stimuli-responsive biosurfaces and biointerfaces, which have been prepared through a combination of cyclodextrin- or cucurbituril-based host–guest chemistry and various surface technologies such as self-assembled monolayers or layer-by-layer assembly. Moreover, we discuss the applications of these biointerfaces and biosurfaces in the fields of drug release, reversible adsorption and release of some organic molecules, peptides, proteins, and cells, and photoswitchable bioelectrocatalysis. In addition, we summarize the merits and current limitations of these methods for fabricating multifunctional stimuli-responsive biointerfaces in a dynamic noncovalent manner. Finally, we present possible strategies for future designs of stimuli-responsive multifunctional biointerfaces and biosurfaces by combining host–guest chemistry with surface science, which will lead to further critical development of supramolecular chemistry at interfaces.
Co-reporter:Seán T. J. Ryan ; Jesús Del Barrio ; Indrajit Ghosh ; Frank Biedermann ; Alexandra I. Lazar ; Yang Lan ; Roger J. Coulston ; Werner M. Nau
Journal of the American Chemical Society 2014 Volume 136(Issue 25) pp:9053-9060
Publication Date(Web):June 3, 2014
DOI:10.1021/ja5032437
We report the self-assembly of a series of highly charged supramolecular complexes in aqueous media composed of cyclobis(4,4′-(1,4-phenylene)bispyridine-p-phenylene)tetrakis(chloride) (ExBox) and three dicationic perylene diimides (PDIs). Efficient energy transfer (ET) is observed between the host and guests. Additionally, we show that our hexacationic complexes are capable of further complexation with neutral cucurbit[7]uril (CB[7]), producing a 3-polypseudorotaxane via the self-assembly of orthogonal recognition moieties. ExBox serves as the central ring, complexing to the PDI core, while two CB[7]s behave as supramolecular stoppers, binding to the two outer quaternary ammonium motifs. The formation of the 3-polypseudorotaxane results in far superior photophysical properties of the central PDI unit relative to the binary complexes at stoichiometric ratios. Lastly, we also demonstrate the ability of our binary complexes to act as a highly selective chemosensing ensemble for the neurotransmitter melatonin.
Co-reporter:Jason R. McKee;Eric A. Appel;Jani Seitsonen;Eero Kontturi;Olli Ikkala
Advanced Functional Materials 2014 Volume 24( Issue 18) pp:2706-2713
Publication Date(Web):
DOI:10.1002/adfm.201303699
Nanocomposite hydrogels are prepared combining polymer brush-modified ‘hard’ cellulose nanocrystals (CNC) and ‘soft’ polymeric domains, and bound together by cucurbit[8]uril (CB[8]) supramolecular crosslinks, which allow dynamic host–guest interactions as well as selective and simultaneous binding of two guests, i.e., methyl viologen (the first guest) and naphthyl units (the second guest). CNCs are mechanically strong colloidal rods with nanometer-scale lateral dimensions, which are functionalized by surface-initiated atom transfer radical polymerization to yield a dense set of methacrylate polymer brushes bearing naphthyl units. They can then be non-covalently cross-linked through simple addition of poly(vinyl alcohol) polymers containing pendant viologen units as well as CB[8]s in aqueous media. The resulting supramolecular nanocomposite hydrogels combine three important criteria: high storage modulus (G′ > 10 kPa), rapid sol–gel transition (<6 s), and rapid self-healing even upon aging for several months, as driven by balanced colloidal reinforcement as well as the selectivity and dynamics of the CB[8] three-component supramolecular interactions. Such a new combination of properties for stiff and self-healing hydrogel materials suggests new approaches for advanced dynamic materials from renewable sources.
Co-reporter:Xian Jun Loh, Jesús del Barrio, Tung-Chun Lee and Oren A. Scherman
Chemical Communications 2014 vol. 50(Issue 23) pp:3033-3035
Publication Date(Web):07 Jan 2014
DOI:10.1039/C3CC49074B
The synthesis of a supramolecular double hydrophilic peptide-conjugated polymer held together by cucurbit[8]uril (CB[8]) ternary complexation and its subsequent temperature triggered self-assembly into vesicles are described. Basic fibroblast growth factor can be easily loaded into the vesicles under benign conditions and their bioactivities can be preserved without the need for excipients such as heparin.
Co-reporter:Frank Biedermann, Ian Ross and Oren A. Scherman
Polymer Chemistry 2014 vol. 5(Issue 18) pp:5375-5382
Publication Date(Web):02 Jun 2014
DOI:10.1039/C4PY00627E
The rate enhancement of the [4 + 4]-photodimerisation of anthracene through a host–guest templation strategy in water is presented and applied to polymer ligation and cross-linking. The macrocycle cucurbit[8]uril (CB[8]) tethers together two anthracene moieties in a face-to-face π–π-stack arrangement, which results in significantly faster photochemical dimerisation (on the order of a few minutes) than in the absence of the host, minimises photochemical side reactions and works even under dilute conditions. Therefore, the host-accelerated photodimerisation was applied to macromolecules, shown here for anthracene end-group functionalised poly(ethylene glycol) (PEG) and side-chain functionalised hydroxyethyl cellulose (HEC) to induce polymer-ligation and network-formation (hydrogelation), respectively. In particular, only in the presence of CB[8] did polymer-ligation or chemical cross-linking through photodimerisation occur, whereas photochemical degradation reactions were exclusively observed in the absence of the CB[8] host.
Co-reporter:Yang Lan;Yuchao Wu;Dr. Athan Karas ; Oren A. Scherman
Angewandte Chemie 2014 Volume 126( Issue 8) pp:2198-2201
Publication Date(Web):
DOI:10.1002/ange.201309204
Abstract
Hybrid raspberry-like colloids (HRCs) were prepared by employing cucurbit[8]uril (CB[8]) as a supramolecular linker to assemble functional polymeric nanoparticles onto a silica core. The formed HRCs are photoresponsive and can be reversibly disassembled upon light irradiation. This facile supramolecular approach provides a platform for the synthesis of colloids with sophisticated structures and properties.
Co-reporter:Yang Lan;Yuchao Wu;Dr. Athan Karas ; Oren A. Scherman
Angewandte Chemie International Edition 2014 Volume 53( Issue 8) pp:2166-2169
Publication Date(Web):
DOI:10.1002/anie.201309204
Abstract
Hybrid raspberry-like colloids (HRCs) were prepared by employing cucurbit[8]uril (CB[8]) as a supramolecular linker to assemble functional polymeric nanoparticles onto a silica core. The formed HRCs are photoresponsive and can be reversibly disassembled upon light irradiation. This facile supramolecular approach provides a platform for the synthesis of colloids with sophisticated structures and properties.
Co-reporter:Eric A. Appel, Rebecca A. Forster, Matthew J. Rowland, Oren A. Scherman
Biomaterials 2014 35(37) pp: 9897-9903
Publication Date(Web):
DOI:10.1016/j.biomaterials.2014.08.001
Co-reporter:Chi Hu, Yang Lan, Feng Tian, Kevin R. West, and Oren A. Scherman
Langmuir 2014 Volume 30(Issue 36) pp:10926-10932
Publication Date(Web):August 29, 2014
DOI:10.1021/la5026125
Surface-immobilized rotaxanes are of practical interest for myriad applications including molecular rotors and analytical sensing. Herein, we present a facile method for the preparation of cucurbit[8]uril (CB[8])-based rotaxanes on gold (Au) surfaces threaded onto a viologen (MV2+) axle. The surface-bound CB[8] rotaxanes were characterized by contact angle measurements and optical microscopy. Direct imaging of the rotaxanes was accomplished by attaching either azobenzene-functionalized silica (Si-azo) colloids or fluorescein-labeled dopamine that were bound to the Au surface through a supramolecular heteroternary (1:1:1) complex with CB[8]. The surface density of CB[8] rotaxanes was examined based on their detection of dopamine. The calculated surface density is 4.8 × 1013 molecules·cm–2, which is only slightly lower than the theoretical value of 5.0 × 1013 molecules·cm–2. Surface-functionalized rotaxanes can be reversibly switched using external stimuli to bind electron-rich second guests for CB[8], including both small molecules such as dopamine and appropriately-functionalized colloidal particles. Such controlled reversibility gives rise to potential applications including selective sensing or reusable templates for preparing well-defined colloidal arrays. The formation of the surface-bound rotaxane structure is critical for successfully anchoring CB[8] host molecules onto Au substrates, yielding an interlocked architecture and preventing the dissociation of binary host–guest complex MV2+⊂CB[8]. The MV2+⊂CB[8] rotaxane structure thus effectively maintains the material density on the Au surface and dramatically enhances the stability of the functional surface.
Co-reporter:Emma-Rose Janeček;Julia Sedlmair;David R. Spring;Alexandros Koutsioubas;Carol J. Hirschmugl;Zarah Walsh;Jonathan R. Nitschke;James T. Hodgkinson;Chris Toprakcioglu;Mark Jones;Martin Welch
PNAS 2014 Volume 111 (Issue 50 ) pp:17743-17748
Publication Date(Web):2014-12-16
DOI:10.1073/pnas.1406037111
The preservation of our cultural heritage is of great importance to future generations. Despite this, significant problems
have arisen with the conservation of waterlogged wooden artifacts. Three major issues facing conservators are structural instability
on drying, biological degradation, and chemical degradation on account of Fe3+-catalyzed production of sulfuric and oxalic acid in the waterlogged timbers. Currently, no conservation treatment exists
that effectively addresses all three issues simultaneously. A new conservation treatment is reported here based on a supramolecular
polymer network constructed from natural polymers with dynamic cross-linking formed by a combination of both host-guest complexation
and a strong siderophore pendant from a polymer backbone. Consequently, the proposed consolidant has the ability to chelate
and trap iron while enhancing structural stability. The incorporation of antibacterial moieties through a dynamic covalent
linkage into the network provides the material with improved biological resistance. Exploiting an environmentally compatible
natural material with completely reversible chemistries is a safer, greener alternative to current strategies and may extend
the lifetime of many culturally relevant waterlogged artifacts around the world.
Co-reporter:Richard W. Taylor, Roger J. Coulston, Frank Biedermann, Sumeet Mahajan, Jeremy J. Baumberg, and Oren A. Scherman
Nano Letters 2013 Volume 13(Issue 12) pp:5985-5990
Publication Date(Web):November 4, 2013
DOI:10.1021/nl403164c
We demonstrate a powerful SERS-nanoreactor concept composed of self-assembled gold nanoparticles (AuNP) linked by the sub-nm macrocycle cucurbit[n]uril (CB[n]). The CB[n] functions simultaneously as a nanoscale reaction vessel, sequestering and templating a photoreaction within, and also as a powerful SERS-transducer through the large field enhancements generated within the nanojunctions that CB[n]s define. Through the enhanced Raman fingerprint, the real-time SERS-monitoring of a prototypical stilbene photoreaction is demonstrated. By choosing the appropriate CB[n] nanoreactor, selective photoisomerism or photodimerization is monitored in situ from within the AuNP-CB[n] nanogap.
Co-reporter:Jesús del Barrio ; Peter N. Horton ; Didier Lairez ; Gareth O. Lloyd ; Chris Toprakcioglu
Journal of the American Chemical Society 2013 Volume 135(Issue 32) pp:11760-11763
Publication Date(Web):July 23, 2013
DOI:10.1021/ja406556h
Herein we report the photocontrol of cucurbit[8]uril (CB[8])-mediated supramolecular polymerization of azobenzene-containing monomers. The CB[8] polymers were characterized both in solution and in the solid state. These host–guest complexes can be reversibly switched between highly thermostable photostationary states. Moreover, a remarkable stabilization of Z-azobenzene was achieved by CB[8] complexation, allowing for structural characterization in the solid state.
Co-reporter:Matthew J. Rowland, Eric A. Appel, Roger J. Coulston and Oren A. Scherman
Journal of Materials Chemistry A 2013 vol. 1(Issue 23) pp:2904-2910
Publication Date(Web):30 Apr 2013
DOI:10.1039/C3TB20180E
Hydrogels, an increasingly important class of material, have physical properties amenable to many potential uses, particularly in the biomedical area. Utilisation of hydrogels, however, relies not only on their mechanical properties but also on a favourable toxicity profile. Self assembly of polymers through naturally occurring and non-toxic units is therefore a very attractive option. The aromatic amino acids phenylalanine and tryptophan are two such molecular units that form 2:1 complexes with cucurbit[8]uril (CB[8]) with high binding equilibrium constants (Keq up to 1012 M−2). Herein, water soluble styrenic monomers were copolymerised with synthetically derived aromatic amino acid monomers of phenylalanine and tryptophan. The resulting polymers were shown to form dynamic and self-healing physically crosslinked hydrogels via recognition and binding of the amino acids to cucurbit[8]uril.
Co-reporter:Samuel T. Jones, Jameel M. Zayed and Oren A. Scherman
Nanoscale 2013 vol. 5(Issue 12) pp:5299-5302
Publication Date(Web):23 Apr 2013
DOI:10.1039/C3NR01454A
We have shown, for the first time, that a three component system is capable of aligning gold nanorods (AuNRs) through supramolecular host–guest interactions leading to control over AuNR end-to-end assembly. Viologen end-functionalised AuNRs were prepared that were capable of selectively binding to a cucurbit[8]uril (CB[8]) macrocyclic host molecule. These end-functionalised AuNRs could participate in 1:1:1 ternary complexation with synthesised telechelic linker molecules bearing second guest moieties, in the presence of CB[8]. When the linker length was long and flexible aggregation and precipitation of AuNRs were readily observed, but with no control over the AuNR conformation. On the other hand, when the linker length was shortened thereby imparting a more rigid connection between neighboring gold nanorods, the end-to-end assembly of AuNRs was achieved. We also note that in the presence of a molecule capable of occupying the entirety of the CB[8] cavity, end-to-end assembly is not observed as the system's ability to form a 1:1:1 ternary complex is halted. Thus, the end-to-end assembly relies upon both having a relatively short and rigid linker as well as the specific, yet tuneable supramolecular 1:1:1 ternary complexation between the three components.
Co-reporter:Silvia Sonzini, Seán T. J. Ryan and Oren A. Scherman
Chemical Communications 2013 vol. 49(Issue 78) pp:8779-8781
Publication Date(Web):05 Aug 2013
DOI:10.1039/C3CC45420G
Pentapeptides containing a Phe residue in the middle of the sequence exhibit ternary complex formation in the presence of cucurbit[8]uril, thus opening new perspectives on supramolecular peptide dimerisation studies.
Co-reporter:Emma-Rose Jane&x10d;ek;Urs Rauwald;Jesús del Barrio;Monika Cziferszky
Macromolecular Rapid Communications 2013 Volume 34( Issue 19) pp:1547-1553
Publication Date(Web):
DOI:10.1002/marc.201300453
Co-reporter:Eric A. Appel, Jesús del Barrio, Xian Jun Loh and Oren A. Scherman
Chemical Society Reviews 2012 vol. 41(Issue 18) pp:6195-6214
Publication Date(Web):13 Aug 2012
DOI:10.1039/C2CS35264H
The supramolecular crosslinking of polymer chains in water by specific, directional and dynamic non-covalent interactions has led to the development of novel supramolecular polymeric hydrogels. These aqueous polymeric networks constitute an interesting class of soft materials exhibiting attractive properties such as stimuli-responsiveness and self-healing arising from their dynamic behaviour and that are crucial for a wide variety of emerging applications. We present here a critical review summarising the formation of dynamic polymeric networks through specific non-covalent interactions, with a particular emphasis on those systems based on host–guest complex formation, as well as the characterisation of their physical characteristics. Aqueous supramolecular chemistry has unlocked a versatile toolbox for the design and fine-tuning of the material properties of these hydrogels (264 references).
Co-reporter:Setu Kasera, Frank Biedermann, Jeremy J. Baumberg, Oren A. Scherman, and Sumeet Mahajan
Nano Letters 2012 Volume 12(Issue 11) pp:5924-5928
Publication Date(Web):October 22, 2012
DOI:10.1021/nl303345z
We show how the macrocyclic host, cucurbit[8]uril (CB[8]), creates precise subnanometer junctions between gold nanoparticles while its cavity simultaneously traps small molecules; this enables their reproducible surface-enhanced Raman spectroscopy (SERS) detection. Explicit shifts in the SERS frequencies of CB[8] on complexation with guest molecules provides a direct strategy for absolute quantification of a range of molecules down to 10–11 M levels. This provides a new analytical paradigm for quantitative SERS of small molecules.
Co-reporter:Eric A. Appel ; Xian Jun Loh ; Samuel T. Jones ; Frank Biedermann ; Cecile A. Dreiss
Journal of the American Chemical Society 2012 Volume 134(Issue 28) pp:11767-11773
Publication Date(Web):June 14, 2012
DOI:10.1021/ja3044568
Hydrogels are three-dimensional networked materials that are similar to soft biological tissues and have highly variable mechanical properties, making them increasingly important in a variety of biomedical and industrial applications. Herein we report the preparation of extremely high water content hydrogels (up to 99.7% water by weight) driven by strong host–guest complexation with cucurbit[8]uril (CB[8]). Cellulosic derivatives and commodity polymers such as poly(vinyl alcohol) were modified with strongly binding guests for CB[8] ternary complex formation (Keq = 1012 M–2). When these polymers were mixed in the presence of CB[8], whereby the overall solid content was 90% cellulosic, a lightly colored, transparent hydrogel was formed instantaneously. The supramolecular nature of these hydrogels affords them with highly tunable mechanical properties, and the dynamics of the CB[8] ternary complex cross-links allows for rapid self-healing of the materials after damage caused by deformation. Moreover, these hydrogels display responsivity to a multitude of external stimuli, including temperature, chemical potential, and competing guests. These materials are easily processed, and the simplicity of their preparation, their availability from inexpensive renewable resources, and the tunability of their properties are distinguishing features for many important water-based applications.
Co-reporter:Eric A. Appel, Jesús del Barrio, Joseph Dyson, Lyle Isaacs and Oren A. Scherman
Chemical Science 2012 vol. 3(Issue 7) pp:2278-2281
Publication Date(Web):18 Apr 2012
DOI:10.1039/C2SC20285A
We present the preparation of metastable single-chain polymeric nanoparticles through stimuli-responsive and reversible intramolecular cross-linking of a single polymer chain in water. Functionalisation of poly(N-hydroxyethylacrylamide) polymers with viologen, followed by addition of nor-seco-cucurbit[10]uril allows for facile preparation of nanoparticles through specific and tightly binding 2:1 homo-ternary complexes. Particle sizes can be readily tuned through either polymer molecular weight or degree of cross-linking. By virtue of the supramolecular nature of the intramolecular cross-linking in water, the formation of these metastable nanoparticles represents a step towards the development of synthetic polymers with aqueous phase behaviour analogous to the self folding of biomacromolecules.
Co-reporter:Dezhi Jiao and Oren A. Scherman
Green Chemistry 2012 vol. 14(Issue 9) pp:2445-2449
Publication Date(Web):19 Jun 2012
DOI:10.1039/C2GC35283D
A method for isolating cucurbit[n]uril (CB[n]) homologues (CB[5–8]) has been developed by utilising several selective imidazolium salts. Complexation with CB[7] and CB[8] causes a dramatic increase in their solubility in water, allowing for facile separation of CB[5] and CB[6] from their corresponding mixtures. The larger homologues (CB[7] and CB[8]) can then be isolated as pure, uncomplexed macrocycles via a solid state metathesis (SSM) ion exchange reaction. Moreover, the imidazolium salts can be readily recycled after CB[n] purification, leading to a near-quantitative recovery loop and providing a “green” isolation process. This methodology remarkably increases the isolated yields of each of the major CB[n] components, reduces the time required for purification, and is amenable to scale-up, which would represent a significant improvement in the field of macrocycles.
Co-reporter:Nan Zhao, Gareth O. Lloyd and Oren A. Scherman
Chemical Communications 2012 vol. 48(Issue 25) pp:3070-3072
Publication Date(Web):20 Jan 2012
DOI:10.1039/C2CC17433B
Monohydroxylated cucurbit[6]uril was prepared for the first time through the controlled oxidation of CB[6] in the presence of a tailor-made bisimidazolium guest, as verified by 1H NMR, ESI-MS and X-ray crystallography. Further chemical modification of monohydroxylated CB[6] was also readily achieved.
Co-reporter:Eric A. Appel, Matthew J. Rowland, Xian Jun Loh, Richard M. Heywood, Colin Watts and Oren A. Scherman
Chemical Communications 2012 vol. 48(Issue 79) pp:9843-9845
Publication Date(Web):30 Aug 2012
DOI:10.1039/C2CC35131E
Temozolomide (TMZ) is the primary chemotherapeutic agent for treatment of glioblastoma multiforme (GBM) yet it has a fast rate of degradation under physiological conditions to the ‘active’ MTIC, which has poor penetration of the blood–brain barrier and cellular absorption. Herein we have demonstrated binding of TMZ within the cavity of nano-container cucurbit[7]uril, resulting in a decreased rate of drug degradation. Prolonging the lifetime of the TMZ under physiological conditions through encapsulation dramatically improved the drug's activity against primary GBM cell lines as more TMZ could be absorbed by the cells before degradation. This work can potentially lead to increases in the drug's propensity for crossing the blood–brain barrier and absorption into the GBM cells, thereby increasing the efficacy of this chemotherapy.
Co-reporter:Yang Lan, Xian Jun Loh, Jin Geng, Zarah Walsh and Oren A. Scherman
Chemical Communications 2012 vol. 48(Issue 70) pp:8757-8759
Publication Date(Web):26 Jul 2012
DOI:10.1039/C2CC34016J
Core–shell polymeric microspheres with a cleavable shell were prepared in water using cucurbit[8]uril to bring together functional polymeric microspheres and functional polymers. This supramolecular approach was employed to switch the cytotoxicity of the polymeric microspheres, leading to potential applications in the eradication of cancer cells.
Co-reporter:Xian Jun Loh, Mei-Hsuan Tsai, Jesús del Barrio, Eric A. Appel, Tung-Chun Lee and Oren A. Scherman
Polymer Chemistry 2012 vol. 3(Issue 11) pp:3180-3188
Publication Date(Web):17 Aug 2012
DOI:10.1039/C2PY20380D
The synthesis of a supramolecular double hydrophilic glucose responsive block copolymer (DHBC) held together by cucurbit[8]uril (CB[8]) ternary complexation and its subsequent self-assembly into micelles is described. The supramolecular block copolymer assembly consists of poly(N-isopropylacrylamide) (PNIPAAm) and poly(acrylamidophenyl boronic acid) (PAAPBA) as temperature and glucose responsive blocks, respectively, and poly(dimethylacrylamide) (PDMAAm) as a hydrophilic block. Drug release studies of insulin-loaded micelles using three external triggers were studied with release of insulin achieved by changing temperature, glucose concentration or by adding a competitive guest for CB[8]. This system offers good control over the release of insulin under physiological conditions (pH 7.4, 37 °C). These exciting results suggest that this system could be a model for a clinically relevant drug delivery vehicle for diabetic treatment.
Co-reporter:Monika Cziferszky, Frank Biedermann, Markus Kalberer and Oren A. Scherman
Organic & Biomolecular Chemistry 2012 vol. 10(Issue 12) pp:2447-2452
Publication Date(Web):10 Jan 2012
DOI:10.1039/C2OB06954G
Aqueous supramolecular chemistry and highly controlled self-assembly of multi-component architectures are novel tools for investigating and answering questions with different biological implications. Among other self-assembly motifs the barrel-shaped host molecule cucurbit[8]uril (CB[8]) is of particular interest due to its capability of incorporating two guest molecules simultaneously in its hydrophobic cavity. This allows for its use as a supramolecular linking unit to conjugate two different entities such as polymers, peptides, and proteins as well as conjugation of various species to surfaces, colloids and nanoparticles. This study aims to improve our understanding of CB[8] ternary complex formation and stability. A series of CB[8] architectures of different size and chemistry have been analyzed in the gas phase to obtain information about their stability in the absence of solvent effects. While hydrophobic effects and solvation energies play a crucial role for host–guest affinities in solution, gas phase stabilities are determined by the guest's ability to form hydrogen bonding and electrostatic interactions. Increasing the size of the second guest resulted in an increase of gas phase stability, likely due to additional non-covalent interactions.
Co-reporter:Jing Zhang;Roger J. Coulston;Samuel T. Jones;Jin Geng;Chris Abell
Science 2012 Volume 335(Issue 6069) pp:690-694
Publication Date(Web):10 Feb 2012
DOI:10.1126/science.1215416
Co-reporter:Eric A. Appel;Jesús del Barrio;Xian Jun Loh;Joseph Dyson
Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 1) pp:181-186
Publication Date(Web):
DOI:10.1002/pola.25041
Abstract
Through the use of copper (I) chloride (CuCl) and tris(2-dimethylaminoethyl)amine (Me6-TREN) as a metal/ligand pair, conditions for the robust, fast, and controlled radical polymerization of high molecular weight N-hydroxyethylacrylamide (HEAm),N-isopropylacrylamide (NIPAm), N,N′-dimethylacrylamide (DMAm), and acrylamide (Am) at ambient temperature are reported. Linear evolution of molecular weight and narrow molecular weight distribution was observed for all monomers with degrees of polymerization ranging from 50 to 5000. Random copolymers of several acrylamide-based monomers are also reported with excellent control over molecular weight and polydispersity. Characterization of high molecular weight poly (NIPAm) demonstrated large changes in the lower critical solution temperature observed on heating and cooling, and this hysteresis was exploited for the controlled release of doxorubicin from poly(NIPAm) spheres. This study represents the first example of preparation of high molecular weight acrylamide polymers by a metal-mediated controlled radical polymerization technique. Access to these materials, as well as to NIPAm polymers in particular, opens new doors for interesting applications in a variety of fields including tissue engineering, drug delivery, and controlled solution viscosity. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Co-reporter:Frank Biedermann;Einat Elmalem;Indrajit Ghosh;Dr. Werner M. Nau;Dr. Oren A. Scherman
Angewandte Chemie 2012 Volume 124( Issue 31) pp:
Publication Date(Web):
DOI:10.1002/ange.201205393
Co-reporter:Frank Biedermann;Einat Elmalem;Indrajit Ghosh;Dr. Werner M. Nau;Dr. Oren A. Scherman
Angewandte Chemie 2012 Volume 124( Issue 31) pp:7859-7863
Publication Date(Web):
DOI:10.1002/ange.201202385
Co-reporter:Eric A. Appel;Joseph Dyson;Dr. Jesús delBarrio;Dr. Zarah Walsh ;Dr. Oren A. Scherman
Angewandte Chemie 2012 Volume 124( Issue 17) pp:4261-4265
Publication Date(Web):
DOI:10.1002/ange.201108659
Co-reporter:Dezhi Jiao;Jin Geng;Xian Jun Loh;Debapratim Das;Tung-Chun Lee;Dr. Oren A. Scherman
Angewandte Chemie 2012 Volume 124( Issue 38) pp:9771-9775
Publication Date(Web):
DOI:10.1002/ange.201202947
Co-reporter:Xian Jun Loh, Jesús del Barrio, Pearl Pei Chern Toh, Tung-Chun Lee, Dezhi Jiao, Urs Rauwald, Eric A. Appel, and Oren A. Scherman
Biomacromolecules 2012 Volume 13(Issue 1) pp:
Publication Date(Web):December 13, 2011
DOI:10.1021/bm201588m
The synthesis of a supramolecular double hydrophilic block copolymer (DHBC) held together by cucurbit[8]uril (CB[8]) ternary complexation and its subsequent self-assembly into micelles is described. This system is responsive to multiple external triggers including temperature, pH and the addition of a competitive guest. The supramolecular block copolymer assembly consists of poly(N-isopropylacrylamide) (PNIPAAm) as a thermoresponsive block and poly(dimethylaminoethylmethacrylate) (PDMAEMA) as a pH-responsive block. Moreover, encapsulation and controlled drug release was demonstrated with this system using the chemotherapeutic drug doxorubicin (DOX). This triple stimuli-responsive DHBC micelle system represents an evolution over conventional double stimuli-responsive covalent diblock copolymer systems and displayed a significant reduction in the viability of HeLa cells upon triggered release of DOX from the supramolecular micellar nanocontainers.
Co-reporter:Frank Biedermann and Oren A. Scherman
The Journal of Physical Chemistry B 2012 Volume 116(Issue 9) pp:2842-2849
Publication Date(Web):February 6, 2012
DOI:10.1021/jp2110067
A supramolecular self-assembly approach is described which allows for the convenient preparation of a wide range of charge-transfer (CT) donor–acceptor complexes in aqueous solutions. When one equiv of the macrocyclic host cucurbit[8]uril (CB[8]) is added to an aqueous donor and acceptor solution, a heteroternary complex forms inside the host’s cavity with a well-defined face-to-face π–π-stacking geometry of the donor and acceptor. This heteroternary, CB[8]-mediated complex offers the opportunity to study the CT phenomena at low concentrations and free from complications arising from any donor–donor and acceptor–acceptor interactions as a result of the large binding affinities and the very high selectivity over the formation of these homoternary complexes. Thus, this supramolocular self-assembly strategy is a practical donor–acceptor mix-and-match approach with synthetic advantages over much more cumbersome tethering schemes. While the characteristic UV/vis features of a few CB[8] ternary systems had been described as a CT band, we present for the first time systematic evidence for the existence of CT interactions between several donor–acceptor pairs that are mediated by the host CB[8]. Correlation of the experimentally obtained CT λmax to computed HOMO–LUMO energies demonstrated that the CT process in the host’s cavity can be described by the Mulliken model. Furthermore, the literature claim of a “CT driving force” for the formation of CB[8] ternary complexes was scrutinized and evaluated by calorimetric (ITC) and ESI-MS measurements. The findings indicated that neither in the aqueous medium nor in the “gas-phase” is CT of energetic relevance to the Gibbs free binding energy. In contrast, electrostatic considerations combined with solvation effects are much better suited to rationalize the observed trends in binding affinities. Additionally, the CT λmax was found to be much more red-shifted (≥75 nm) inside the CB[8] cavity than in any polar organic solvents or water, indicating a significant stabilization of the CT excited state within the host cavity, further demonstrating the unique electrostatic, polar properties of the host cavity.
Co-reporter:Eric A. Appel, Xian Jun Loh, Samuel T. Jones, Cecile A. Dreiss, Oren A. Scherman
Biomaterials 2012 33(18) pp: 4646-4652
Publication Date(Web):
DOI:10.1016/j.biomaterials.2012.02.030
Co-reporter:Tung-Chun Lee ;Dr. Oren A. Scherman
Chemistry - A European Journal 2012 Volume 18( Issue 6) pp:1628-1633
Publication Date(Web):
DOI:10.1002/chem.201102675
Abstract
Supramolecular capping of cucurbit[n]uril (CB[n]), where n=5–8, by narrowly dispersed gold nanoparticles has been achieved through a facile synthetic route with metastable gold nanoparticles as a labile intermediate. The resultant assemblies were stable in solution, and were found to form dynamic aggregates consisting of a controllable ratio of singly and doubly capped CB[n]. The stability of the system was attributed to the presence of sodium cations bound on the vacant carbonyl portals of the singly capped CB[n] molecules. These dynamically capped CB[n] systems can find potential use in a range of applications varying from ultrasensitive multiplexed in situ sensing to photocatalysis.
Co-reporter:Eric A. Appel;Joseph Dyson;Dr. Jesús delBarrio;Dr. Zarah Walsh ;Dr. Oren A. Scherman
Angewandte Chemie International Edition 2012 Volume 51( Issue 17) pp:4185-4189
Publication Date(Web):
DOI:10.1002/anie.201108659
Co-reporter:Frank Biedermann;Einat Elmalem;Indrajit Ghosh;Dr. Werner M. Nau;Dr. Oren A. Scherman
Angewandte Chemie International Edition 2012 Volume 51( Issue 31) pp:
Publication Date(Web):
DOI:10.1002/anie.201205393
Co-reporter:Frank Biedermann;Einat Elmalem;Indrajit Ghosh;Dr. Werner M. Nau;Dr. Oren A. Scherman
Angewandte Chemie International Edition 2012 Volume 51( Issue 31) pp:7739-7743
Publication Date(Web):
DOI:10.1002/anie.201202385
Co-reporter:Dezhi Jiao;Jin Geng;Xian Jun Loh;Debapratim Das;Tung-Chun Lee;Dr. Oren A. Scherman
Angewandte Chemie International Edition 2012 Volume 51( Issue 38) pp:9633-9637
Publication Date(Web):
DOI:10.1002/anie.201202947
Co-reporter:Frank Biedermann, Urs Rauwald, Jameel M. Zayed and Oren A. Scherman
Chemical Science 2011 vol. 2(Issue 2) pp:279-286
Publication Date(Web):18 Oct 2010
DOI:10.1039/C0SC00435A
The supramolecular formation of a PEGylated bovine serum albumin (BSA) protein-polymer bio-conjugate in water has been demonstrated through a selective host–guest interaction with the macrocycle cucurbit[8]uril (CB[8]). Both BSA and poly(ethylene glycol) were functionalised with either an electron-deficient first guest viologen or an electron-rich second guest naphthalene for the formation of the CB[8] ternary complex. With the help of spectroscopic (NMR, DOSY-NMR, DLS, UV/vis, fluorescence) and calorimetric (ITC) techniques, it was shown that a strong and specific binding interaction took place between the complementary labeled polymer and protein only in the presence of the macrocyclic host CB[8]. Moreover, we demonstrated that controlled formation of a supramolecular protein-protein complex was also possible through the use of CB[8] ternary formation.
Co-reporter:Urs Rauwald, Jesús del Barrio, Xian Jun Loh and Oren A. Scherman
Chemical Communications 2011 vol. 47(Issue 21) pp:6000-6002
Publication Date(Web):12 Apr 2011
DOI:10.1039/C1CC11214G
The chain end complexation of a functional PNIPAM by a cucurbit[8]uril-viologen complex causes a shift in its lower critical solution temperature (LCST) by over 5 °C. An instantaneous phase change of the thermally responsive polymer beyond its LCST can be induced by addition of the aqueous cucurbituril host–guest complex. Subsequent decomplexation upon addition of a competitive guest releases the PNIPAM terminus and triggers complete reversibility.
Co-reporter:Roger J. Coulston, Samuel T. Jones, Tung-Chun Lee, Eric A. Appel and Oren A. Scherman
Chemical Communications 2011 vol. 47(Issue 1) pp:164-166
Publication Date(Web):14 Sep 2010
DOI:10.1039/C0CC03250F
A gold nanoparticle–polymer composite material has been prepared in water using cucurbit[8]uril as a supramolecular “handcuff” to hold together viologen-functionalised gold nanoparticles and a naphthol-functionalised acrylamide copolymer.
Co-reporter:Dezhi Jiao, Frank Biedermann, and Oren A. Scherman
Organic Letters 2011 Volume 13(Issue 12) pp:3044-3047
Publication Date(Web):May 19, 2011
DOI:10.1021/ol200911w
A series of bisimidazolium salts were synthesized as novel guests for the macrocyclic host molecule cucurbit[8]uril (CB[8]). These bisimidazolium-CB[8] binary complexes exhibited a unique cage structure with the imidazolium rings acting as lids, leading to a size-dependent binding selectivity by altering the hydrophobic linker between the two imidazolium moieties. This new class of CB[8] complexes was also capable of binding small solvent molecules, including acetone, acetonitrile, diethyl ether, and tetrahydrofuran (THF) in an aqueous environment.
Co-reporter:Feng Tian, Monika Cziferszky, Dezhi Jiao, Karolina Wahlström, Jin Geng, and Oren A. Scherman
Langmuir 2011 Volume 27(Issue 4) pp:1387-1390
Publication Date(Web):December 31, 2010
DOI:10.1021/la104346k
We demonstrate a supramolecular peptide separation approach by the selective immobilization of peptides bearing an N-terminal tryptophan onto a CB[8]-modified gold substrate, followed by electrochemical release. The CB[8]-stabilized heteroternary complexes were characterized by 1H NMR, ESI-MS, UV/vis, and fluorescence spectroscopy and cyclic voltammetry. Micropatterned CB[8]-modified gold substrates were found to trap only the recognizable N-tryptophan-containing peptides from a peptide mixture that could be visualized as green peptide arrays under fluorescence microscopy. Subsequently, the bound peptides were released from the modified substrates by the controlled single-electron reduction of viologen. The fully reversible trap-and-release process was repeated for 13 cycles, and the cumulative release profile of the dye−peptide conjugate was monitored by fluorescence spectroscopy, indicating that no degradation occurred.
Co-reporter:Frank Biedermann, Eric A. Appel, Jesús del Barrio, Till Gruendling, Christopher Barner-Kowollik, and Oren A. Scherman
Macromolecules 2011 Volume 44(Issue 12) pp:4828-4835
Publication Date(Web):May 26, 2011
DOI:10.1021/ma2008018
The postpolymerization functionalization of hydroxyl-group terminated polymers (Mn in the range of 1000–6000 g mol–1) such as poly(ethylene glycol) (PEG), poly(N-isopropylacrylamide) (PNIPAM), poly(N,N-dimethylacrylamide) (PDMAM), and poly(tert-butyl acrylate) (PtBA) with a wide range of functional isocyanate derivatives such as azobenzene, viologen, and anthracene has been investigated. It was shown by 1H and 13C NMR, GPC, Fourier transform infrared spectroscopy (FTIR), and electrospray ionization mass spectrometry (ESI-MS) that a high degree of end-group conversion, typically >98%, with little or no formation of side products can be achieved at ambient temperature. PNIPAM, PDMAM, PtBA, and PHEAM polymers have been obtained by reversible addition–fragmentation chain transfer (RAFT) radical polymerization from a hydroxyl-group containing chain transfer agent (CTA). The formation of the carbamate has been shown to be compatible with the trithiocarbonate end-group of the RAFT polymers. Additionally, this approach allows for the direct functionalization of RAFT polymers without the need of additional steps such as deprotection or aminolysis of the CTA. This route was subsequently used for the preparation of a variety of side-chain functional polymers from poly(N-hydroxyethyl acrylamide) (PHEAM). Three different high yielding methods have been employed to prepare the isocyanates (R–NCO). Either amino or carboxylic acid precursors have been converted into the desired R–NCO or hydroxyl group moieties have been reacted with an excess of 1,6-hexamethylene diisocyanate (HDI) to statistically form the monofunctional product.
Co-reporter:Jin Geng, Frank Biedermann, Jameel M. Zayed, Feng Tian, and Oren A. Scherman
Macromolecules 2011 Volume 44(Issue 11) pp:4276-4281
Publication Date(Web):May 6, 2011
DOI:10.1021/ma200343q
Supramolecular self-assembly and reversible switching has been demonstrated for the first time between monovalent and multivalent carbohydrate ligands and the multivalency effect on lectin binding has been investigated. The self-assembly process is mediated through noncovalent interactions between pendant moieties on a polymer scaffold and a monosaccharide-functionalized viologen with cucurbit[8]uril (CB[8]) acting as a “supramolecular handcuff”. The rate of binding of the tetrameric lectin Concanavalin A (Con A) to a mannose-containing supramolecular glycopolymer was investigated through a standard turbidimetric assay.
Co-reporter:Jameel M. Zayed, Nicolas Nouvel, Urs Rauwald and Oren A. Scherman
Chemical Society Reviews 2010 vol. 39(Issue 8) pp:2806-2816
Publication Date(Web):29 Jun 2010
DOI:10.1039/B922348G
Aqueous supramolecular chemistry, the non-covalent assembly of simple building blocks into higher ordered architectures in water has received much focus recently. Biological systems are able to form complex, and well-defined microstructures essential to cellular function, and supramolecular chemistry has demonstrated its utility in assembling molecules to form increasingly complex assemblies. This tutorial review will summarise non-covalent building blocks based on both synthetic and biological systems in an aqueous environment, emphasising the complexity of the assemblies formed. Examples of higher ordered assemblies will be highlighted, from supramolecular plastics to spider silks, towards more compartmentalised protocell precursors.
Co-reporter:Dezhi Jiao ; Frank Biedermann ; Feng Tian
Journal of the American Chemical Society 2010 Volume 132(Issue 44) pp:15734-15743
Publication Date(Web):October 14, 2010
DOI:10.1021/ja106716j
The assembly behavior of aryl/alkyl imidazolium ionic liquid salts in aqueous solution has been investigated. These salts undergo self-assembly into one-dimensional stacks via hydrophobic and π−π interactions upon increasing concentration, which led to a substantial increase in the solution viscosity in water. Addition of the macrocyclic host molecules cucurbit[n]urils (CB[n]) were found to effectively alter the supramolecular assemblies, as evidenced from the dramatic increase (by CB[7]) and decrease (by CB[8]) in solution viscosity and aggregation size in water, on account of the different binding stoichiometries, 1:1 complexation with CB[7] and 2:1 complexation with CB[8]. Furthermore, the aggregate architectures were controllably modified by competitive guests for the CB[n] hosts. This complex supramolecular systems approach has tremendous implications in the fields of molecular sensor design, nonlinear viscosity modification, and controlled release of target molecules from a defined supramolecular scaffold in water.
Co-reporter:Eric A. Appel ; Frank Biedermann ; Urs Rauwald ; Samuel T. Jones ; Jameel M. Zayed
Journal of the American Chemical Society 2010 Volume 132(Issue 40) pp:14251-14260
Publication Date(Web):September 16, 2010
DOI:10.1021/ja106362w
The ability to finely tune the solution viscosity of an aqueous system is critical in many applications ranging from large-scale fluid-based industrial processes to free-standing hydrogels important in regenerative medicine, controlled drug delivery, and ‘green’ self-healing materials. Herein we demonstrate the use of the macrocyclic host molecule cucurbit[8]uril (CB[8]) to facilitate reversible cross-linking of multivalent copolymers with high binding constants (Ka > 1011−1012 M−2) leading to a supramolecular hydrogel. Multivalent copolymers were prepared by free radical polymerization techniques and contained either pendant methyl viologen (a good first guest for CB[8]) or naphthoxy derivatives (good second guests for CB[8]). A colorless solution of the two multivalent copolymers bearing first and second guests, respectively, can be transformed into a highly viscous, colored supramolecular hydrogel with the cross-link density being easily controlled through CB[8] addition. Moreover, the cross-links (1:1:1 supramolecular ternary complexes of CB[8]/viologen/naphthoxy) are dynamic and stimuli-responsive, and the material properties can be modulated by temperature or other external stimuli. Rheological characterization of the bulk material properties of these dynamically cross-linked networks provided insight into the kinetics of CB[8] ternary complexation responsible for elastically active cross-linking with a second guest dissociation rate constant (kd) of 1200 s−1 for the ternary complex. These materials exhibited intermediate mechanical properties at 5 wt % in water (plateau modulus = 350−600 Pa and zero-shear viscosity = 5−55 Pa·s), which is complementary to existing supramolecular hydrogels. Additionally, these supramolecular hydrogels exhibited thermal reversibility and subsequent facile modulation of microstructure upon further addition of CB[8] and thermal treatment. The fundamental knowledge gained from the study of these dynamic materials will facilitate progress in the field of smart, self-healing materials, self-assembled hydrogels, and controlled solution viscosity.
Co-reporter:Dezhi Jiao, Nan Zhao and Oren A. Scherman
Chemical Communications 2010 vol. 46(Issue 12) pp:2007-2009
Publication Date(Web):11 Jan 2010
DOI:10.1039/B920848H
A method to isolate CB[7] from a CB[5]/CB[7] mixture has been successfully developed by incorporating an alkyl-imidazolium ionic liquid guest of the type [Cnmim]Br which is only capable of binding with CB[7]. This CB[7]–[Cnmim]Br complex can be removed from the mixture and a subsequent solid state ion metathesis affords pure CB[7]. Moreover, the imidazolium ionic liquids can be recycled from the aqueous solution after the purification thus providing a ‘green’ process.
Co-reporter:Tung-Chun Lee and Oren A. Scherman
Chemical Communications 2010 vol. 46(Issue 14) pp:2438-2440
Publication Date(Web):27 Jan 2010
DOI:10.1039/B925051D
Supramolecular capping of cucurbit[5]uril (CB[5]) by gold nanoparticles has been achieved via a facile reduction of an aqueous solution of HAuCl4 by NaBH4 in the presence of various amounts of CB[5]. The resultant assemblies were very stable in solution, and were found to form dynamic aggregates consisting of a controllable ratio of singly and doubly capped CB[5].
Co-reporter:Jameel M. Zayed, Frank Biedermann, Urs Rauwald and Oren A. Scherman
Polymer Chemistry 2010 vol. 1(Issue 9) pp:1434-1436
Publication Date(Web):07 Sep 2010
DOI:10.1039/C0PY00197J
Diffusion NMR and solution viscometry were used to probe the cucurbit[8]uril-mediated host–guest self assembly of multiple molecular guests to form 5-component supramolecular ABA triblock copolymers in aqueous solution.
Co-reporter:Sumeet Mahajan, Tung-Chun Lee, Frank Biedermann, James T. Hugall, Jeremy J. Baumberg and Oren A. Scherman
Physical Chemistry Chemical Physics 2010 vol. 12(Issue 35) pp:10429-10433
Publication Date(Web):25 Jun 2010
DOI:10.1039/C0CP00071J
Cucurbit[n]urils (CB[n]) are a family of supramolecular hosts which can provide highly selective recognition based on their size (n). In this work we study their Raman spectroscopic signatures both experimentally and by molecular simulation and find systematic trends providing evidence of ring strain effects with size. Furthermore, we present for the first time their surface-enhanced Raman scattering (SERS) spectra utilizing both nanostructured surface and nanoparticle based approaches. Using SERS we can detect CB[n] at the ppb level and are able to distinguish between them in mixtures. Our study paves the way for utilization of CB[n] in highly sensitive, multiplexed, real time and high throughput molecular recognition assays based on SERS.
Co-reporter:Adam D. Celiz
Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 24) pp:5833-5841
Publication Date(Web):
DOI:10.1002/pola.24391
Abstract
Three new ureidopyrimidinone(UPy)-functionalized chain-transfer agents (CTAs) have been synthesized for use in reversible addition-fragmentation chain transfer (RAFT) polymerization. These UPy-CTAs are able to polymerize a wide variety of vinyl monomers to yield UPy-functionalized polymers, including homopolymers, block copolymers, and amphiphilic block copolymers. These polymers have been characterized via 1H and 13C NMR spectroscopy, gel permeation chromatography (GPC), UV/visible spectroscopy and differential scanning calorimetry (DSC) to demonstrate end-group fidelity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Co-reporter:Nan Zhao;Li Liu Dr.;Frank Biedermann ;OrenA. Scherman Dr.
Chemistry – An Asian Journal 2010 Volume 5( Issue 3) pp:530-537
Publication Date(Web):
DOI:10.1002/asia.200900510
Abstract
The host–guest chemistry between a series of 1-alkyl-3-methyl-imidazolium bromide ([Cnmim]Br) guests and the macrocyclic host molecule cucurbit[6]uril (CB[6]) in an aqueous system is systematically studied in neutral aqueous media. Both 1D and 2D NMR experiments in conjunction with isothermal titration calorimetry (ITC) unveil the binding characteristics of the host–guest interaction. Solution binding constants (Ka) up to 105 M−1 are measured directly. Additionally, this [Cnmim]Br–CB[6] interaction was found to significantly increase the solubility of CB[6] in neutral water, in some cases by at least four orders of magnitude. From these studies, a detailed host-guest binding model has been constructed and is fully discussed. In this model, the delocalized positive charge on the imidazolium ring becomes partially localized on either one of the nitrogen atoms upon complexation with CB[6]. Localization of the positive charge is directly related to the length of the “1-alkyl” chain on the imidazolium ring, which causes an induced local dipole subsequently allowing for an ion–dipole interaction with the carbonyl portal of CB[6].
Co-reporter:Urs Rauwald, Frank Biedermann, Stéphanie Deroo, Carol V. Robinson and Oren A. Scherman
The Journal of Physical Chemistry B 2010 Volume 114(Issue 26) pp:8606-8615
Publication Date(Web):June 15, 2010
DOI:10.1021/jp102933h
The high-throughput characterization of solution binding equilibria is essential in biomedical research such as drug design as well as in material applications of synthetic systems in which reversible binding interactions play critical roles. Although isothermal titration calorimetry (ITC) has been widely employed for describing such binding events, factors such as speed, concentration, and sample complexity would principally favor a mass spectrometry approach. Here, we show a link between ITC and electrospray ionization mass spectrometry (ESI-MS) by incorporating solvation free energies in the study of the ternary complexes of the macrocyclic host cucurbit[8]uril (CB[8]). The binding affinities of 32 aromatic reference complexes were studied by ITC and ESI-MS and combined with solvation data of the guests from an implicit solvation model (SM8) to obtain a correlation between aqueous and gas-phase measurements. The data illustrates the critical importance of solvation on the binding strength in CB[8]’s ternary complexes. Finally, this treatment enabled us to predict association constants that were in excellent agreement with measured values, including several highly insoluble guest compounds.
Co-reporter:Feng Tian, Nan Cheng, Nicolas Nouvel, Jin Geng and Oren A. Scherman
Langmuir 2010 Volume 26(Issue 8) pp:5323-5328
Publication Date(Web):March 25, 2010
DOI:10.1021/la9033386
We have examined hierarchical supramolecular structure in the formation of colloidal arrays by immobilizing monodispersed naphthalene-functionalized colloids onto Au substrates bearing viologen moieties using the macrocyclic host molecule cucurbit[8]uril as a supramolecular “handcuff”. Naphthalene-functionalized poly(methyl methacrylate)- and polystyrene-based colloids were synthesized by soap-free emulsion polymerization and characterized by dynamic light scattering and scanning electron microscopy to realize the colloidal arrays and to facilitate direct macroscopic imaging. The formation of host-stabilized ternary complexes on the surface of naphthalene-functionalized microspheres in colloidal suspension was verified by titration of a preformed viologen−CB[8] complex and followed by zeta potential measurements. Patterned self-assembled monolayers of a viologen derivative on Au substrates were formed by backfilling viologen-modified thiols after spontaneous chemisorption of “protective” alkylthiols by microcontact printing. After the initial complexation of CB[8] onto the viologen derivative on the Au substrates, monolayers of colloids with both 1D and 2D patterns could be formed and characterized by contact angle measurement, optical microscopy, and scanning electron microscopy. Control experiments indicated that no colloids were attached to the Au substrate after moderate washing by water if (1) CB[8] was replaced by a smaller analogue of the macrocyclic host, CB[6] or CB[7], (2) colloids without naphthalene-functionalities on the periphery were employed, or (3) alkanethiol was used entirely instead of viologenthiol to protect the Au substrate. These results suggest that the supramolecular ternary complexes were key to successfully bind the colloids onto the Au substrates with the CB[8] acts as a supramolecular “handcuff”. The fundamental expertise gained from the study of these materials is believed to facilitate progress in the field of smart materials and wet nanotechnology and lead to the preparation of controlled reversible architectures on surfaces.
Co-reporter:Frank Biedermann;Urs Rauwald;Dr. Monika Cziferszky;Dr. Kyle A. Williams;Lauren D. Gann;Bi Y. Guo; Adam R. Urbach; Christopher W. Bielawski;Dr. Oren A. Scherman
Chemistry - A European Journal 2010 Volume 16( Issue 46) pp:13716-13722
Publication Date(Web):
DOI:10.1002/chem.201002274
Abstract
The utilities of benzobis(imidazolium) salts (BBIs) as stable and fluorescent components of supramolecular assemblies involving the macrocyclic host, cucurbit[8]uril (CB[8]), are described. CB[8] has the unusual ability to bind tightly and selectively to two different guests in aqueous media, typically methyl viologen (MV) as the first guest, followed by an indole, naphthalene, or catechol-containing second guest. Based on similar size, shape, and charge, tetramethyl benzobis(imidazolium) (MBBI) was identified as a potential alternative to MV that would increase the repertoire of guests for cucurbit[8]uril. Isothermal titration calorimetry (ITC) studies showed that MBBI binds to CB[8] in a 1:1 ratio with an equilibrium association constant (Ka) value of 5.7×105 M−1, and that the resulting MBBI⋅CB[8] complex binds to a series of aromatic second guests with Ka values ranging from 103 to 105 M−1. These complexation phenomena were supported by mass spectrometry, which confirmed complex formation, and a series of NMR studies that showed the expected upfield perturbation of aromatic peaks and of the MBBI methyl peaks. Surprisingly, the binding behavior of MBBI is strikingly similar to that of MV, and yet MBBI offers a number of substantial advantages for many applications, including intrinsic fluorescence, high chemical stability, and broad synthetic tunability. Indeed, the intense fluorescence emission of the MBBI⋅CB[8] complex was quenched upon binding to the second guests, thus demonstrating the utility of MBBI as a component for optical sensing. Building on these favorable properties, the MBBI⋅CB[8] system was successfully applied to the sequence-selective recognition of peptides as well as the controlled disassembly of polymer aggregates in water. These results broaden the available guests for the cucurbit[n]uril family and demonstrate potentially new applications.
Co-reporter:Adam D. Celiz;Tung-Chun Lee
Advanced Materials 2009 Volume 21( Issue 38-39) pp:3937-3940
Publication Date(Web):
DOI:10.1002/adma.200901291
Co-reporter:Stéphanie Deroo, Urs Rauwald, Carol V. Robinson and Oren A. Scherman
Chemical Communications 2009 (Issue 6) pp:644-646
Publication Date(Web):06 Jan 2009
DOI:10.1039/B818369D
The formation of modular, multi-component, host–guest complexes stable both in water and in the gas-phase is described; by modulating the stoichiometry of the different subunits in aqueous solution, quantitative self-assembly of the predicted and desired architecture is achieved, even allowing for ABA triblock copolymer assemblies stable in the gas-phase.
Co-reporter:Li Liu, Nicolas Nouvel and Oren A. Scherman
Chemical Communications 2009 (Issue 22) pp:3243-3245
Publication Date(Web):24 Apr 2009
DOI:10.1039/B903033F
For the first time a lid-free and charge-free inclusion complex with cucurbit[6]uril (CB[6]) has been isolated, the crystal structure is reported and the robust nature of the complex is demonstrated in the solid state while facile controlled release of the guest is achieved in solution.
Co-reporter:Li Liu, Nan Zhao and Oren A. Scherman
Chemical Communications 2008 (Issue 9) pp:1070-1072
Publication Date(Web):02 Jan 2008
DOI:10.1039/B716889F
Cucurbit[6]uril was dissolved through encapsulation of an imidazolium-based ionic liquid guest in a pure water environment and the dissolution ability could be tuned by augmenting the imidazolium structure.
Co-reporter:Urs Rauwald ;OrenA. Scherman Dr.
Angewandte Chemie 2008 Volume 120( Issue 21) pp:
Publication Date(Web):
DOI:10.1002/ange.200890096
Co-reporter:Urs Rauwald ;OrenA. Scherman Dr.
Angewandte Chemie 2008 Volume 120( Issue 21) pp:4014-4017
Publication Date(Web):
DOI:10.1002/ange.200705591
Co-reporter:Urs Rauwald ;OrenA. Scherman Dr.
Angewandte Chemie International Edition 2008 Volume 47( Issue 21) pp:3950-3953
Publication Date(Web):
DOI:10.1002/anie.200705591
Co-reporter:Urs Rauwald ;OrenA. Scherman Dr.
Angewandte Chemie International Edition 2008 Volume 47( Issue 21) pp:
Publication Date(Web):
DOI:10.1002/anie.200890096
Co-reporter:Adam D. Celiz and Oren A. Scherman
Macromolecules 2008 Volume 41(Issue 12) pp:4115-4119
Publication Date(Web):May 20, 2008
DOI:10.1021/ma702699t
Controlled anionic ring-opening polymerization of ϵ-caprolactone (ϵ-CL) in toluene using self-complementary quadruple hydrogen bonding array 2-ureido-4[1H]-pyrimidinone (UPy)-functionalized initiators with stannous(II) octanoate has been achieved to yield UPy−poly(ϵ-caprolactone) chains capable of undergoing supramolecular self-assembly. Molecular weights of these polymers varied from 2000 to 20 000 g/mol and were determined using 1H NMR end-group analysis as well as gel permeation chromatography. Furthermore, using Ubbelohde solution viscometry, samples demonstrated a marked increase in viscosity-average molecular weight when measured in chloroform, indicating that the UPy chain ends are in a dimerized form when compared to polymer solutions in dimethylformamide (DMF).
Co-reporter:Sumeet Mahajan, Tung-Chun Lee, Frank Biedermann, James T. Hugall, Jeremy J. Baumberg and Oren A. Scherman
Physical Chemistry Chemical Physics 2010 - vol. 12(Issue 35) pp:NaN10433-10433
Publication Date(Web):2010/06/25
DOI:10.1039/C0CP00071J
Cucurbit[n]urils (CB[n]) are a family of supramolecular hosts which can provide highly selective recognition based on their size (n). In this work we study their Raman spectroscopic signatures both experimentally and by molecular simulation and find systematic trends providing evidence of ring strain effects with size. Furthermore, we present for the first time their surface-enhanced Raman scattering (SERS) spectra utilizing both nanostructured surface and nanoparticle based approaches. Using SERS we can detect CB[n] at the ppb level and are able to distinguish between them in mixtures. Our study paves the way for utilization of CB[n] in highly sensitive, multiplexed, real time and high throughput molecular recognition assays based on SERS.
Co-reporter:Chi Hu, Yu Zheng, Ziyi Yu, Chris Abell and Oren A. Scherman
Chemical Communications 2015 - vol. 51(Issue 23) pp:NaN4860-4860
Publication Date(Web):2015/02/11
DOI:10.1039/C5CC00121H
The fabrication, characterisation and controlled burst release of naphthol-functionalised micellar (NFM) nanostructures, which were grafted onto gold surfaces through cucurbit[8]uril (CB[8]) mediated host–guest interactions are described. NFMs undergo a facile change in morphology from micelles to diblock copolymers in direct response to exposure to organic solvents, including tetrahydrofuran (THF), toluene and chloroform. This induced transition in conformation lends itself to potential applications including nanocarriers for triggered burst-release of guest molecules. Nile Red was investigated as a NFM encapsulated model hydrophobic cargo inside the surface-attached micelles, which could be fully released upon exposure to THF as measured by both atomic force microscopy and UV/vis spectroscopy.
Co-reporter:Yang Lan, Xian Jun Loh, Jin Geng, Zarah Walsh and Oren A. Scherman
Chemical Communications 2012 - vol. 48(Issue 70) pp:NaN8759-8759
Publication Date(Web):2012/07/26
DOI:10.1039/C2CC34016J
Core–shell polymeric microspheres with a cleavable shell were prepared in water using cucurbit[8]uril to bring together functional polymeric microspheres and functional polymers. This supramolecular approach was employed to switch the cytotoxicity of the polymeric microspheres, leading to potential applications in the eradication of cancer cells.
Co-reporter:Eric A. Appel, Matthew J. Rowland, Xian Jun Loh, Richard M. Heywood, Colin Watts and Oren A. Scherman
Chemical Communications 2012 - vol. 48(Issue 79) pp:NaN9845-9845
Publication Date(Web):2012/08/30
DOI:10.1039/C2CC35131E
Temozolomide (TMZ) is the primary chemotherapeutic agent for treatment of glioblastoma multiforme (GBM) yet it has a fast rate of degradation under physiological conditions to the ‘active’ MTIC, which has poor penetration of the blood–brain barrier and cellular absorption. Herein we have demonstrated binding of TMZ within the cavity of nano-container cucurbit[7]uril, resulting in a decreased rate of drug degradation. Prolonging the lifetime of the TMZ under physiological conditions through encapsulation dramatically improved the drug's activity against primary GBM cell lines as more TMZ could be absorbed by the cells before degradation. This work can potentially lead to increases in the drug's propensity for crossing the blood–brain barrier and absorption into the GBM cells, thereby increasing the efficacy of this chemotherapy.
Co-reporter:Li Liu, Nan Zhao and Oren A. Scherman
Chemical Communications 2008(Issue 9) pp:NaN1072-1072
Publication Date(Web):2008/01/02
DOI:10.1039/B716889F
Cucurbit[6]uril was dissolved through encapsulation of an imidazolium-based ionic liquid guest in a pure water environment and the dissolution ability could be tuned by augmenting the imidazolium structure.
Co-reporter:Matthew J. Rowland, Eric A. Appel, Roger J. Coulston and Oren A. Scherman
Journal of Materials Chemistry A 2013 - vol. 1(Issue 23) pp:NaN2910-2910
Publication Date(Web):2013/04/30
DOI:10.1039/C3TB20180E
Hydrogels, an increasingly important class of material, have physical properties amenable to many potential uses, particularly in the biomedical area. Utilisation of hydrogels, however, relies not only on their mechanical properties but also on a favourable toxicity profile. Self assembly of polymers through naturally occurring and non-toxic units is therefore a very attractive option. The aromatic amino acids phenylalanine and tryptophan are two such molecular units that form 2:1 complexes with cucurbit[8]uril (CB[8]) with high binding equilibrium constants (Keq up to 1012 M−2). Herein, water soluble styrenic monomers were copolymerised with synthetically derived aromatic amino acid monomers of phenylalanine and tryptophan. The resulting polymers were shown to form dynamic and self-healing physically crosslinked hydrogels via recognition and binding of the amino acids to cucurbit[8]uril.
Co-reporter:Monika Cziferszky, Frank Biedermann, Markus Kalberer and Oren A. Scherman
Organic & Biomolecular Chemistry 2012 - vol. 10(Issue 12) pp:NaN2452-2452
Publication Date(Web):2012/01/10
DOI:10.1039/C2OB06954G
Aqueous supramolecular chemistry and highly controlled self-assembly of multi-component architectures are novel tools for investigating and answering questions with different biological implications. Among other self-assembly motifs the barrel-shaped host molecule cucurbit[8]uril (CB[8]) is of particular interest due to its capability of incorporating two guest molecules simultaneously in its hydrophobic cavity. This allows for its use as a supramolecular linking unit to conjugate two different entities such as polymers, peptides, and proteins as well as conjugation of various species to surfaces, colloids and nanoparticles. This study aims to improve our understanding of CB[8] ternary complex formation and stability. A series of CB[8] architectures of different size and chemistry have been analyzed in the gas phase to obtain information about their stability in the absence of solvent effects. While hydrophobic effects and solvation energies play a crucial role for host–guest affinities in solution, gas phase stabilities are determined by the guest's ability to form hydrogen bonding and electrostatic interactions. Increasing the size of the second guest resulted in an increase of gas phase stability, likely due to additional non-covalent interactions.
Co-reporter:Xian Jun Loh, Jesús del Barrio, Tung-Chun Lee and Oren A. Scherman
Chemical Communications 2014 - vol. 50(Issue 23) pp:NaN3035-3035
Publication Date(Web):2014/01/07
DOI:10.1039/C3CC49074B
The synthesis of a supramolecular double hydrophilic peptide-conjugated polymer held together by cucurbit[8]uril (CB[8]) ternary complexation and its subsequent temperature triggered self-assembly into vesicles are described. Basic fibroblast growth factor can be easily loaded into the vesicles under benign conditions and their bioactivities can be preserved without the need for excipients such as heparin.
Co-reporter:Jameel M. Zayed, Nicolas Nouvel, Urs Rauwald and Oren A. Scherman
Chemical Society Reviews 2010 - vol. 39(Issue 8) pp:NaN2816-2816
Publication Date(Web):2010/06/29
DOI:10.1039/B922348G
Aqueous supramolecular chemistry, the non-covalent assembly of simple building blocks into higher ordered architectures in water has received much focus recently. Biological systems are able to form complex, and well-defined microstructures essential to cellular function, and supramolecular chemistry has demonstrated its utility in assembling molecules to form increasingly complex assemblies. This tutorial review will summarise non-covalent building blocks based on both synthetic and biological systems in an aqueous environment, emphasising the complexity of the assemblies formed. Examples of higher ordered assemblies will be highlighted, from supramolecular plastics to spider silks, towards more compartmentalised protocell precursors.
Co-reporter:Silvia Sonzini, Seán T. J. Ryan and Oren A. Scherman
Chemical Communications 2013 - vol. 49(Issue 78) pp:NaN8781-8781
Publication Date(Web):2013/08/05
DOI:10.1039/C3CC45420G
Pentapeptides containing a Phe residue in the middle of the sequence exhibit ternary complex formation in the presence of cucurbit[8]uril, thus opening new perspectives on supramolecular peptide dimerisation studies.
Co-reporter:Nan Zhao, Gareth O. Lloyd and Oren A. Scherman
Chemical Communications 2012 - vol. 48(Issue 25) pp:NaN3072-3072
Publication Date(Web):2012/01/20
DOI:10.1039/C2CC17433B
Monohydroxylated cucurbit[6]uril was prepared for the first time through the controlled oxidation of CB[6] in the presence of a tailor-made bisimidazolium guest, as verified by 1H NMR, ESI-MS and X-ray crystallography. Further chemical modification of monohydroxylated CB[6] was also readily achieved.
Co-reporter:Anna Andreou, Michal Leskes, Pablo G. Jambrina, Gary J. Tustin, Clare P. Grey, Edina Rosta and Oren A. Scherman
Chemical Science (2010-Present) 2015 - vol. 6(Issue 11) pp:NaN6269-6269
Publication Date(Web):2015/08/06
DOI:10.1039/C4SC02729A
The hydroboration 1,3- and 1,4-cyclic dienes has been systematically investigated. The behavior of such dienes towards mono and dihydroboration was monitored directly by 11B NMR to identify the actual boron species formed, as opposed to the most common analysis of the resultant oxidation products. Quantitative dihydroboration was achieved for the full range of cyclic dienes investigated including dienes, which were previously reported to be resistant to dihydroboration, leading to the formation of new boron-containing polymeric materials. The conditions favoring dihydroboration are reported as well as full characterisation of the materials. Furthermore, a hydroboration cascade mechanism is proposed for the formation of such boron-containing polymers, supported by both experimental and theoretical data.
Co-reporter:Tung-Chun Lee and Oren A. Scherman
Chemical Communications 2010 - vol. 46(Issue 14) pp:NaN2440-2440
Publication Date(Web):2010/01/27
DOI:10.1039/B925051D
Supramolecular capping of cucurbit[5]uril (CB[5]) by gold nanoparticles has been achieved via a facile reduction of an aqueous solution of HAuCl4 by NaBH4 in the presence of various amounts of CB[5]. The resultant assemblies were very stable in solution, and were found to form dynamic aggregates consisting of a controllable ratio of singly and doubly capped CB[5].
Co-reporter:Dezhi Jiao, Nan Zhao and Oren A. Scherman
Chemical Communications 2010 - vol. 46(Issue 12) pp:NaN2009-2009
Publication Date(Web):2010/01/11
DOI:10.1039/B920848H
A method to isolate CB[7] from a CB[5]/CB[7] mixture has been successfully developed by incorporating an alkyl-imidazolium ionic liquid guest of the type [Cnmim]Br which is only capable of binding with CB[7]. This CB[7]–[Cnmim]Br complex can be removed from the mixture and a subsequent solid state ion metathesis affords pure CB[7]. Moreover, the imidazolium ionic liquids can be recycled from the aqueous solution after the purification thus providing a ‘green’ process.
Co-reporter:Roger J. Coulston, Samuel T. Jones, Tung-Chun Lee, Eric A. Appel and Oren A. Scherman
Chemical Communications 2011 - vol. 47(Issue 1) pp:NaN166-166
Publication Date(Web):2010/09/14
DOI:10.1039/C0CC03250F
A gold nanoparticle–polymer composite material has been prepared in water using cucurbit[8]uril as a supramolecular “handcuff” to hold together viologen-functionalised gold nanoparticles and a naphthol-functionalised acrylamide copolymer.
Co-reporter:Urs Rauwald, Jesús del Barrio, Xian Jun Loh and Oren A. Scherman
Chemical Communications 2011 - vol. 47(Issue 21) pp:NaN6002-6002
Publication Date(Web):2011/04/12
DOI:10.1039/C1CC11214G
The chain end complexation of a functional PNIPAM by a cucurbit[8]uril-viologen complex causes a shift in its lower critical solution temperature (LCST) by over 5 °C. An instantaneous phase change of the thermally responsive polymer beyond its LCST can be induced by addition of the aqueous cucurbituril host–guest complex. Subsequent decomplexation upon addition of a competitive guest releases the PNIPAM terminus and triggers complete reversibility.
Co-reporter:Frank Biedermann, Urs Rauwald, Jameel M. Zayed and Oren A. Scherman
Chemical Science (2010-Present) 2011 - vol. 2(Issue 2) pp:NaN286-286
Publication Date(Web):2010/10/18
DOI:10.1039/C0SC00435A
The supramolecular formation of a PEGylated bovine serum albumin (BSA) protein-polymer bio-conjugate in water has been demonstrated through a selective host–guest interaction with the macrocycle cucurbit[8]uril (CB[8]). Both BSA and poly(ethylene glycol) were functionalised with either an electron-deficient first guest viologen or an electron-rich second guest naphthalene for the formation of the CB[8] ternary complex. With the help of spectroscopic (NMR, DOSY-NMR, DLS, UV/vis, fluorescence) and calorimetric (ITC) techniques, it was shown that a strong and specific binding interaction took place between the complementary labeled polymer and protein only in the presence of the macrocyclic host CB[8]. Moreover, we demonstrated that controlled formation of a supramolecular protein-protein complex was also possible through the use of CB[8] ternary formation.
Co-reporter:Chi Hu, Feng Tian, Yu Zheng, Cindy Soo Yun Tan, Kevin R. West and Oren A. Scherman
Chemical Science (2010-Present) 2015 - vol. 6(Issue 9) pp:NaN5310-5310
Publication Date(Web):2015/07/06
DOI:10.1039/C5SC01496D
In situ modification of surfaces with thin layers of polymers is of growing interest as adjustment of surface properties can be made on demand. We present herein a supramolecular ‘grafting to’ polymer brush via the recognition of surface-bound cucurbit[8]uril (CB[8]) rotaxanes towards end-functionalised polyethylene glycol (PEG). This dynamic supramolecular method represents advantages over traditional approaches, which employ covalent bond formation in the ‘grafting to’ process. Brush properties can be easily modified post-preparation by exchanging the polymers with small molecules in a controlled, reversible manner. Including both redox- and light-responsive guests in a single rotaxane entity, the CB[8]-mediated preparation of the polymer brush offers unique opportunities to switch the brush composition efficiently. While the PEG brushes are well hydrated in a good solvent (water) and stretch away from the surface, they collapse in a poor solvent (toluene), leading to the formation of a dense layer on the surface. This collapsed conformation protects the heteroternary complexes of CB[8]-rotaxane from dissociation and maintains the attachment of polymers on the surface.
Co-reporter:Eric A. Appel, Jesús del Barrio, Joseph Dyson, Lyle Isaacs and Oren A. Scherman
Chemical Science (2010-Present) 2012 - vol. 3(Issue 7) pp:NaN2281-2281
Publication Date(Web):2012/04/18
DOI:10.1039/C2SC20285A
We present the preparation of metastable single-chain polymeric nanoparticles through stimuli-responsive and reversible intramolecular cross-linking of a single polymer chain in water. Functionalisation of poly(N-hydroxyethylacrylamide) polymers with viologen, followed by addition of nor-seco-cucurbit[10]uril allows for facile preparation of nanoparticles through specific and tightly binding 2:1 homo-ternary complexes. Particle sizes can be readily tuned through either polymer molecular weight or degree of cross-linking. By virtue of the supramolecular nature of the intramolecular cross-linking in water, the formation of these metastable nanoparticles represents a step towards the development of synthetic polymers with aqueous phase behaviour analogous to the self folding of biomacromolecules.
Co-reporter:Eric A. Appel, Jesús del Barrio, Xian Jun Loh and Oren A. Scherman
Chemical Society Reviews 2012 - vol. 41(Issue 18) pp:NaN6214-6214
Publication Date(Web):2012/08/13
DOI:10.1039/C2CS35264H
The supramolecular crosslinking of polymer chains in water by specific, directional and dynamic non-covalent interactions has led to the development of novel supramolecular polymeric hydrogels. These aqueous polymeric networks constitute an interesting class of soft materials exhibiting attractive properties such as stimuli-responsiveness and self-healing arising from their dynamic behaviour and that are crucial for a wide variety of emerging applications. We present here a critical review summarising the formation of dynamic polymeric networks through specific non-covalent interactions, with a particular emphasis on those systems based on host–guest complex formation, as well as the characterisation of their physical characteristics. Aqueous supramolecular chemistry has unlocked a versatile toolbox for the design and fine-tuning of the material properties of these hydrogels (264 references).
Co-reporter:Li Liu, Nicolas Nouvel and Oren A. Scherman
Chemical Communications 2009(Issue 22) pp:NaN3245-3245
Publication Date(Web):2009/04/24
DOI:10.1039/B903033F
For the first time a lid-free and charge-free inclusion complex with cucurbit[6]uril (CB[6]) has been isolated, the crystal structure is reported and the robust nature of the complex is demonstrated in the solid state while facile controlled release of the guest is achieved in solution.
Co-reporter:Stéphanie Deroo, Urs Rauwald, Carol V. Robinson and Oren A. Scherman
Chemical Communications 2009(Issue 6) pp:NaN646-646
Publication Date(Web):2009/01/06
DOI:10.1039/B818369D
The formation of modular, multi-component, host–guest complexes stable both in water and in the gas-phase is described; by modulating the stoichiometry of the different subunits in aqueous solution, quantitative self-assembly of the predicted and desired architecture is achieved, even allowing for ABA triblock copolymer assemblies stable in the gas-phase.
Co-reporter:R. J. Gubeli, S. Sonzini, A. Podmore, P. Ravn, O. A. Scherman and C. F. van der Walle
Chemical Communications 2016 - vol. 52(Issue 22) pp:NaN4238-4238
Publication Date(Web):2016/02/22
DOI:10.1039/C6CC00405A
The combination of potent chemical moieties with biologically active proteins is key to some of today's most innovative therapeutic drugs. In order to obviate any chemical modification of the proteins, we present a novel and powerful strategy for the selective conjugation of recombinant protein domains with synthetically derived peptides via a cucurbit[8]uril host–guest chemistry approach.
Co-reporter:Silvia Sonzini, Helen F. Stanyon and Oren A. Scherman
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 2) pp:NaN1465-1465
Publication Date(Web):2016/11/30
DOI:10.1039/C6CP06765D
Amyloid β is one of the peptides involved in the onset of Alzheimer's disease, yet the structure of the toxic species and its underlying mechanism remain elusive on account of the dynamic nature of the Aβ oligomerisation process. While it has been reported that incubation of Amyloid β (1–42) sequences (Aβ42) lead to formation of aggregates that vary in morphology and toxicity, we demonstrate that addition of a discrete macrocyclic host molecule, cucurbit[8]uril (CB[8]), substantially reduces toxicity in the neuronal cell line SH-SY5Y. The macrocycle preferentially targets Phe residues in Aβ42 complexing them in a 2:1 fashion in neighboring peptide strands. A small but significant structural ‘switch’ occurs, which induces an increased aggregation rate, suggesting a different cell-uptake mechanism for Aβ42 in the presence of CB[8]. Dramatically increasing the rate of Aβ42 aggregation with CB[8] bypasses the toxic, oligomeric state offering an alternative approach to counter Alzheimer's disease.
Co-reporter:Jade A. McCune, Edina Rosta and Oren A. Scherman
Organic & Biomolecular Chemistry 2017 - vol. 15(Issue 4) pp:NaN1005-1005
Publication Date(Web):2016/12/20
DOI:10.1039/C6OB02594C
The functionalisation of cucurbit[n]uril macrocycles carried out through an oxidative approach in water using ammonium persulfate was studied. Through complexation with a doubly-charged bisimidazolium guest we were able to detect, distinguish and quantify the presence of each CB[n]-(OH)x (where 1 ≤ x ≤ 2n) derivative for the first time. The impact of oxidation on each CB[n] (n = 6–8) was studied individually, as well as in the presence of other competing CB[n] species. We were able to understand the reactivity of the parent CB[n] alongside its hydroxylated derivatives, CB[n]-(OH)x, and show that the oxidation of CB[n] through a free-radical approach cannot result in stoichiometric hydroxylation despite previous literature reports by Bardelang, Ouari and co-workers, J. Am. Chem. Soc., 2015, 137, 10238. Furthermore, an in-depth study on hydroxylation of CB[7] was conducted. Through DFT calculations we were able to show that the second hydroxy substituent is preferentially located on the same glycoluril unit. Moreover, through optimisation of the reaction conditions we were able to access a protocol for controlled oxidation to yield a chemically monofunctional CB[7] derivative.
Co-reporter:Ziyi Yu, Jing Zhang, Roger J. Coulston, Richard M. Parker, Frank Biedermann, Xin Liu, Oren A. Scherman and Chris Abell
Chemical Science (2010-Present) 2015 - vol. 6(Issue 8) pp:NaN4933-4933
Publication Date(Web):2015/06/11
DOI:10.1039/C5SC01440A
Host–guest assembly in droplet-based microfluidics opens a new avenue for fabricating supramolecular hydrogel microcapsules with high monodispersity and controlled functionality. In this paper, we demonstrate a single emulsion microdroplet platform to prepare microcapsules with supramolecular hydrogel skins from host molecule cucurbit[8]uril and guest polymer anthracene-functionalized hydroxyethyl cellulose. In contrast to construction of microcapsules from a droplet-in-droplet double emulsion, here the electrostatic attraction between charged polymer and surfactant facilitates formation of defined supramolecular hydrogel skins in a single emulsion. Furthermore, by taking advantage of dynamic interactions and the tunable cross-linked supramolecular hydrogel network, it is possible to prepare microcapsules with triggered and UV-controlled molecular permeability. These could be potentially used in a delivery system for e.g. agrochemicals, nutraceuticals or cosmetics.
Co-reporter:Alexander S. Groombridge, Aniello Palma, Richard M. Parker, Chris Abell and Oren A. Scherman
Chemical Science (2010-Present) 2017 - vol. 8(Issue 2) pp:NaN1355-1355
Publication Date(Web):2016/10/11
DOI:10.1039/C6SC04103E
The self-assembly of a stimuli-responsive aqueous supramolecular hyperbranched polymer from small molecules is reported. This system is composed of ditopic and tritopic guest-functionalised molecules that are able to form heteroternary supramolecular complexes with the macrocyclic host cucurbit[8]uril (CB[8]). We demonstrate that the supramolecular hyperbranched polymer formed is responsive to both photo- and chemical stimuli, exhibiting reversibility. Furthermore, this system is shown to assemble at liquid–liquid interfaces, which upon gelation, is observable on the micrometre scale. This self-healing supramolecular network can act as a soft matter barrier for aqueous microdroplets, inhibiting their coalescence.
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