Traditionally, containers made from steel or other metals are not good for making tea, probably due to the fact that polyphenol components in tea can chelate with metal ions. A similar reason might stand behind the observations as reported herein. During the coating of well-defined metal–organic framework (MOF) crystalline particles with polydopamine (PDA) via pH-induced self-polymerization of dopamine, we found that MOF templates automatically etch off during the coating, giving rise to nonspherical PDA capsules that inherit the morphologies of the templates. Such self-etching of MOF templates is ascribed to the chelation of the metal nodes of the MOFs by the catechol moieties in the PDA layer. In addition, the self-etching of the zeolitic imidazolate framework-8 (ZIF-8) with a truncated cubic shape probably follows a crystalline facet-dependent fashion, resulting in intermediate yolk–shell structures with ZIF-8 cargos of various shapes inside a highly biocompatible PDA shell. Incubation of such intermediate hybrid particles with the cancerous HeLa cell line leads to pronounced cytotoxicity, which is tentatively connected with the cellular internalization of the ZIF@PDA nanoparticles because of the cell affinity of the PDA layer. Subsequently, the continuous release of Zn2+ by the self-etching of the encapsulated ZIF-8 inside the cell increases intracellular Zn2+ to a harmful level. Therefore, intracellular delivery of metal ions is probably realized, which might offer a novel way for cancer therapy.

Polymeric capsules often buckle, collapse or even break when being processed in the dried state into other materials under high temperature and pressure due to moderate mechanical rigidity. In the case of non-spherical capsules, to keep their precious anisotropic morphology intact under harsh conditions is even more challenging since the whole surface of such kinds of capsules does not experience the same stress or strain due to the different surface curvatures. In the current work, we reported a strategy to prepare polydopamine (PDA) capsules with an ellipsoidal shape and enhanced mechanical rigidity using polystyrene ellipsoids as the sacrificial anisotropic templates. Bio-inspired oxidation induced self-polymerization of dopamine can form conformal PDA coatings on polystyrene ellipsoids of various aspect ratios and sizes. Several strategies have been exploited to increase the thickness of the PDA shell, among which, iterating PDA coating produces ellipsoidal PDA capsules with a thick and robust shell. These ellipsoidal PDA capsules can survive carbonization at temperatures as high as 800 °C and were directly turned into N-doped carbon capsules with a well-defined ellipsoidal shape, excluding the necessity of removing the sacrificial templates after carbonation. Furthermore, the rigid PDA ellipsoidal capsules are efficient adsorbents for organic dyes in contaminated water and have impressive adsorption efficiencies as high as 200 mg g−1.

Understanding the important role of the surface roughness of nano/colloidal particles and harnessing them for practical applications need novel strategies to control the particles’ surface topology. Although there are many examples of spherical particles with a specific surface roughness, nonspherical ones with similar surface features are rare. The current work reports a one-step, straightforward, and bioinspired surface engineering strategy to prepare ellipsoidal particles with a controlled surface roughness. By manipulating the unique chemistry inherent to the oxidation-induced self-polymerization of dopamine into polydopamine (PDA), PDA coating of polymeric ellipsoids leads to a library of hybrid ellipsoidal particles (PS@PDA) with a surface that decorates with nanoscale PDA protrusions of various densities and sizes. Together with the advantages originated from the anisotropy of ellipsoids and rich chemistry of PDA, such a surface feature endows these particles with some unique properties. Evaporative drying of fluorinated PS@PDA particles produces a homogeneous coating with superhydrophobicity that arises from the two-scale hierarchal structure of microscale interparticle packing and nanoscale roughness of the constituent ellipsoids. Instead of water repelling that occurs for most of the lotus leaf-like superhydrophobic surfaces, such coating exhibits strong water adhesion that is observed with certain species of rose pedals. In addition, the as-prepared hybrid ellipsoids are very efficient in preparing liquid marble-isolated droplets covered with solid particles. Such liquid marbles can be placed onto many surfaces and might be useful for the controllable transport and manipulation of small volumes of liquids.Keywords: ellipsoid; liquid marble; polydopamine; superhydrophobicity; surface roughness;

The current work reports an intriguing discovery of how the force exerted on protein complexes like filamentous viruses by the strong interchain repulsion of polymer brushes can induce subtle changes of the constituent subunits at the molecular scale. Such changes transform into the macroscopic rearrangement of the chiral ordering of the rodlike virus in three dimensions. For this, a straightforward “grafting-to” PEGylation method has been developed to densely graft a filamentous virus with poly(ethylene glycol) (PEG). The grafting density is so high that PEG is in the polymer brush regime, resulting in straight and thick rodlike particles with a thin viral backbone. Scission of the densely PEGylated viruses into fragments was observed due to the steric repulsion of the PEG brush, as facilitated by adsorption onto a mica surface. The high grafting density of PEG endows the virus with an isotropic–nematic (I–N) liquid crystal (LC) phase transition that is independent of the ionic strength and the densely PEGylated viruses enter into the nematic LC phase at much lower virus concentrations. Most importantly, while the intact virus and the one grafted with PEG of low grafting density can form a chiral nematic LC phase, the densely PEGylated viruses only form a pure nematic LC phase. This can be traced back to the secondary to tertiary structural change of the major coat protein of the virus, driven by the steric repulsion of the PEG brush. Quantitative parameters characterising the conformation of the grafted PEG derived from the grafting density or the I–N LC transition are elegantly consistent with the theoretical prediction.

Molecular chaperones can elegantly fine-tune its hydrophobic/hydrophilic balance to assist a broad spectrum of nascent polypeptide chains to fold properly. Such precious property is difficult to be achieved by chaperone mimicking materials due to limited control of their surface characteristics that dictate interactions with unfolded protein intermediates. Mixed shell polymeric micelles (MSPMs), which consist of two kinds of dissimilar polymeric chains in the micellar shell, offer a convenient way to fine-tune surface properties of polymeric nanoparticles. In the current work, we have fabricated ca. 30 kinds of MSPMs with finely tunable hydrophilic/hydrophobic surface properties. We investigated the respective roles of thermosensitive and hydrophilic polymeric chains in the thermodenaturation protection of proteins down to the molecular structure. Although the three kinds of thermosensitive polymers investigated herein can form collapsed hydrophobic domains on the micellar surface, we found distinct capability to capture and release unfolded protein intermediates, due to their respective affinity for proteins. Meanwhile, in terms of the hydrophilic polymeric chains in the micellar shell, poly(ethylene glycol) (PEG) excels in assisting unfolded protein intermediates to refold properly via interacting with the refolding intermediates, resulting in enhanced chaperone efficiency. However, another hydrophilic polymer-poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) severely deteriorates the chaperone efficiency of MSPMs, due to its protein-resistant properties. Judicious combination of thermosensitive and hydrophilic chains in the micellar shell lead to MSPM-based artificial chaperones with optimal efficacy.

Controlled and reversible interactions between polymeric nanoparticles and proteins have gained more and more attention with the hope to address many biological issues such as prevention of protein denaturation, interference of the fibrillation of disease relative proteins, removing of toxic biomolecules as well as targeting delivery of proteins, etc. In such cases, proper analytic techniques are needed to reveal the underlying mechanism of the particle-protein interactions. In the current work, Förster Resonance Energy Transfer (FRET) was used to investigate the interaction of our tailor designed artificial chaperone based on mixed shell polymeric micelles (MSPMs) with their substrate proteins. We designed a new kind of MSPMs with fluorescent acceptors precisely placed at the desired locations as well as hydrophobic domains which can adsorb unfolded proteins with a propensity to aggregate. Interactions of such model micelles with a donor-labeled protein-FITC-lysozyme, was monitored by FRET. The fabrication strategy of MSPMs makes it possible to control the accurate location of the acceptor, which is critical to reveal some unexpected insights of the micelle-protein interactions upon heating and cooling. Preadsorption of native proteins onto the hydrophobic domains of the MSPMs is a key step to prevent thermo-denaturation by diminishing interprotein aggregations. Reversible protein adsorption during heating and releasing during cooling have been confirmed. Conclusions from the FRET effect are in line with the measurement of residual enzymatic activity.Keywords: artificial chaperone; Förster resonance energy transfer; mixed shell polymeric micelle; nanoparticle; protein;

Imparting ordered structures into otherwise amorphous hydrogels is expected to endow these popular materials with novel multiple-stimuli responsiveness that promises many applications. The current contribution reports a method to fabricate pure polymeric hydrogels with an inherent chiral internal structure by templating on the chiral nematic liquid crystal phase of a rodlike virus. A method was developed to form macroscopically homogeneous chiral templates by confinement induced self-assembly in the presence of monomers, cross-linkers and initiators. Polymerization induced gelation was performed without perturbing the elegant 3D chiral organization of the rodlike virus bearing double bonds. Furthermore, a suitable method was found to remove the organic virus template while keeping the desired polymeric replica intact, resulting in a pure polymeric hydrogel with a unique internal chiral feature that originates from the 3D chiral ordering of the cylindrical pores left by the virus. Multiple-stimuli responsiveness has been demonstrated and can be quantified by the change of the pitch of the chiral feature. The chiral structure endows the otherwise featureless hydrogel with a unique material property that might be used as a readout signal for sensing and acts as the basis for responsive, biomimetic nanostructured materials.

Hybrid particulate composites consisting of noble metal nanoparticles (NPs) and polymeric particles have attracted intensive interest, due to the possibility of combining the precious optical and catalytic properties of the former with the stimuli responsiveness and biocompatibility of the latter. However, it is challenging to prepare hybrid particles that simultaneously have tunable optical and catalytic properties as well as excellent colloidal stability. In the current work, we report a strategy for such hybrid particles, through covalently decorating the outmost surface of mixed shell polymeric micelles (MSPMs) with gold NPs. For this, two block polymers, poly(ε-caprolactone)-block-(ethylene glycol) (PCL-b-PEG) and poly(ε-caprolactone)-block-poly(N-isopropylacrylamide) (PCL-b-PNIPAM), were prepared by ring-opening polymerization and reversible addition fragmentation chain transfer (RAFT) polymerization, respectively. Co-self-assembly of the two block polymers result in MSPMs with a PCL core and a mixed shell consisting of PEG and PNIPAM. At the end of each PNIPAM chain in the shell, thiol groups are introduced to act as anchors for the in situ formation of gold NPs. The number density of the gold NPs is conveniently tuned through varying the relative amount of PEG/PNIPAM in the micellar shell. Reversible shrinking and extension of the PNIPAM chains regulated by temperature can be used to tune the interparticle distance of the gold NPs, while the whole hybrid particles are stabilized by the stretched PEG chains. The hybrid polymeric micelles exhibit thermoresponsive surface plasmon resonance and enhanced catalytic properties as well as excellent colloidal stability.

The current work investigates the thermoresponsive in situ chiral to nonchiral ordering transformation of a rodlike virus in the naturally assembled state—the chiral nematic liquid crystal (CLC) phase. We take this as an elegant example of reconfigurable self-assembly, through which it is possible to realize in situ transformation from one assembled state to another without disrupting the preformed assembly in general or going through a secondary assembling procedure of the disassembled building blocks. The detailed investigation presented here reveals many unique characteristics of the thermoresponsive 3D chiral ordering of rodlike viruses induced by heat stress. The chiral to nonchiral ordering transformation is highly reversible in the temperature range of up to 60 °C and can be repeated many times. There exists a critical temperature around 40 °C which is independent of the ionic strength and virus concentration. Such reconfigurable ordering in the CLC phase stems from the intrinsic structure change of constituent coat proteins without disrupting the structural integrity of the virus, as revealed by three analytical techniques targeting levels ranging from the molecular, secondary conformation of the constituent proteins to the whole single virus, respectively. Such structural flexibility, also termed polymorphism, is relative to the survival strategies of a biological organism such as the virus and can be transformed into very precious material properties. The potential of the virus-based CLC phase as the chiral matrix to regulate chiro-optical properties of gold nanorods is also presented.

The rodlike M13 viruses with chemically decorated phenylboronic acid moieties form pH responsive chiral nematic liquid crystal (LC) phases. Binding with biologically important diols results in LC phases with microstructures that closely correlate with the molecular structure of the diols and can be conveniently discerned by visual cues.

When smart or responsive polymers are conjugated to biomolecules such as peptides or proteins, the resulting bioconjugates combine both bioactivities of the biomolecules and the responsive properties of the synthetic polymers. Among the responsive polymers, those containing boronic acid or its derivatives are unique due to their affinity to diol-containing compounds and pH dependent amphiphilicity. However, boronic acid containing polymer-based bioconjugates are rare, probably due to the challenges faced in the preparation of such bioconjugates. In this work, we report the synthesis of boronic acid containing polymers with an N-hydroxysuccinidic ester end functional group that can react with amino groups of a protein or peptide. Using a natural protein assembly rod-like M13 virus as a model, we demonstrate the preparation of boronic acid containing polymer–protein bioconjugates. Such virus–polymer bioconjugates can reversibly form hydrogels and the gelation behavior can be regulated by temperature, pH or diol-containing compounds such as glucose. Bioactive species can be loaded inside such hydrogel, and the glucose regulated insulin release is demonstrated under physiological conditions.

Multicompartment polymeric micelles (MPMs) have attracted broad interest, due to their intriguing advantages. Although a plethora of MPMs have been designed recently, characterization of the fine hierarchical compartmented structure and dynamic conformation change of MPMs are still challenging. In this contribution, we reported a strategy to detect thermo-induced structure rearrangement of one kind of MPMs--mixed shell polymeric micelles (MSPMs) and its interaction with bio-targets such as proteins by the means of the 1-anilino-8-naphthalene sulfonate (ANS) fluorescence. It is found that there exists a specific fluorescent emission phenomena characterized by a strong blue-shifted emission maximum and enhanced quantum yield when ANS interacts with MSPMs with a mixed shell consisting of homogeneously mixed poly(ethylene oxide) (PEG) and poly(N-isopropylacryamide) (PNIPAM). Such emission maximum was exploited to probe the structure evolution of MSPMs during the collapse of the thermo-sensitive PNIPAM component by heating. The variation of the emission behavior of ANS during heating is in line with the structure rearrangement of the MSPMs which critically depends on the nature of the micellar core. Binding of a model protein-carbonic anhydrase B (CAB) during heating induced denaturation to the hydrophobic PNIPAM domains of the MSPMs was also reflected by the change of the emission behavior of ANS.

The rodlike M13 viruses with chemically decorated phenylboronic acid moieties form pH responsive chiral nematic liquid crystal (LC) phases. Binding with biologically important diols results in LC phases with microstructures that closely correlate with the molecular structure of the diols and can be conveniently discerned by visual cues.