Co-reporter:Yinan Ma;Ryota Sato;Keiji Numata
Macromolecular Bioscience 2016 Volume 16( Issue 1) pp:
Publication Date(Web):
DOI:10.1002/mabi.201500255
Oligomerization of thiol-unprotected l-cysteine ethyl ester (Cys-OEt) catalyzed by proteinase K in aqueous solution has been used to synthesize oligo(l-cysteine) (OligoCys) with a well-defined chemical structure and relatively large degree of polymerization (DP) up to 16–17 (average 8.8). By using a high concentration of Cys-OEt, 78.0% free thiol content was achieved. The thermal properties of OligoCys are stable, with no glass transition until 200 °C, and the decomposition temperature could be increased by oxidation. Chemoenzymatically synthesized OligoCys has great potential for use as a thermostable bio-based material with resistance to oxidation.
Co-reporter:Yaoming Wan, Zuoning Wang, Jing Sun, and Zhibo Li
Langmuir 2016 Volume 32(Issue 30) pp:7512-7518
Publication Date(Web):July 11, 2016
DOI:10.1021/acs.langmuir.6b00727
Peptide hydrogels with high stability in different media are of great interest in biomedical applications. In this paper, we report an easy, fast, and scalable method for preparing a family of nonionic peptide amphiphiles (PAs) obtained by direct aminolysis of alkyl-oilgo(γ-benzyl-l-glutamate) samples, which were synthesized via the alkyl amine-initiated sequence ring-opening reaction of α-amino acid N-carboxyanhydrides. One great advantage of this method is that vast chemical diversity and large-scale yields can be achieved easily using commercially available hydramines. These PA samples can readily form a clear hydrogel without any external aid and show exceptionally enhanced gelation properties with a critical gelation concentration as low as 0.05 wt %. The hydrogels are highly stable against extreme pH values of 1 and 14 and a high salt concentration of 200 mM NaCl. These properties combined with the shear-thinning properties make these PA hydrogels ideal candidates for the new generation of injectable scaffolds.
Co-reporter:Yinan Ma, Zhibo Li, and Keiji Numata
ACS Biomaterials Science & Engineering 2016 Volume 2(Issue 4) pp:697
Publication Date(Web):March 7, 2016
DOI:10.1021/acsbiomaterials.6b00113
Cell sheets are useful materials in regenerative medicine; however, the cell sheet fabrication processes developed to date are associated with several crucial challenges. The aim of this study was to develop a new and simple method for the rapid and efficient fabrication of transferable monolayer cell sheets. Chemoenzymatic synthesis mediated by proteinase K was used to synthesize short co-oligopeptides for cell sheet fabrication, which showed high yield, well-defined structures, and a controllable composition. These co-oligopeptides predominantly adopted a random coil conformation in buffer. Histidine/cysteine co-oligopeptides with a disordered secondary structure displayed cysteine content-dependent esterase activity and cysteine content-independent protease activity. Taking advantage of this enzymatic activity, confluent cell monolayers were detached by simply adding the co-oligopeptides solution to the culture media, and then an intact monolayer cell sheet was prepared with high cell viability and reattachment ability. The method proposed herein for preparing monolayer cell sheets represents a novel concept by using oligopeptides with enzymatic activity that show applied potential in cell sheet technology for tissue engineering and regenerative medicine.Keywords: chemoenzymatic synthesis; enzymatic activity; monolayer cell sheet; oligopeptides
Co-reporter:Yong Shen, Xiaohui Fu, Wenxin Fu and Zhibo Li
Chemical Society Reviews 2015 vol. 44(Issue 3) pp:612-622
Publication Date(Web):22 Oct 2014
DOI:10.1039/C4CS00271G
The stimuli-responsive polypeptides have drawn extensive attention because of their promising applications in biotechnology considering their biocompatibility, biodegradability, and bioactivity. In this tutorial review, we summarize the most recent progress in this area, including thermo-, redox-, photo-, and biomolecule responsive polypeptides over the past decade. The design and synthesis of stimuli-responsive polypeptides will be briefly introduced. The correlation between the structure and properties, particularly the effects of polypeptide conformation, will be emphasized here. In addition, the applications of stimuli-responsive polypeptides in controlled drug release and tissue engineering are briefly discussed.
Co-reporter:Yong Shen, Shusheng Zhang, Yaoming Wan, Wenxin Fu and Zhibo Li
Soft Matter 2015 vol. 11(Issue 15) pp:2945-2951
Publication Date(Web):19 Feb 2015
DOI:10.1039/C5SM00083A
A second or fourth generation dendrimer with primary amine as the peripheral terminal group was first synthesized via Michael addition and thiol–yne addition. A series of star-shaped polypeptides was synthesized by ring opening polymerization (ROP) of γ-(2-(2-methoxyethoxy)ethyl) L-glutamate (L-EG2Glu) N-carboxyanhydride (NCA) using the amine group terminated dendrimer as the initiator. Taking advantage of the well-defined dendrimer and ROP, the arm number and arm length can be easily controlled. These star-shaped poly(L-EG2Glu) can spontaneously form hydrogels instead of micelles in water at low concentration. The critical gelation concentration (CGC) and hydrogel strength displayed a stronger dependence on arm numbers than the arm length under similar conditions. These properties can be easily modulated by varying the poly(L-EG2Glu) arm length and arm number. The hydrogels showed shear thinning and rapid recovery properties. TEM and AFM characterization revealed that the hydrogel networks were constituted by entangled and branched fibrils.
Co-reporter:Zuoning Wang;Shuang Xia;Hong Chen;Song Wang;Kangming Nie
Polymer International 2015 Volume 64( Issue 8) pp:
Publication Date(Web):
DOI:10.1002/pi.4914
Abstract
A series of biodegradable poly(d-lactide) (PDLA) nanocomposites filled with silica nanoparticles with different surface characteristics were prepared via the solvent casting method. The crystallization behavior of PDLA was investigated at different temperatures. For these hybrid nanocomposites, the effects of silica nanoparticles displayed distinct influences on the crystallization behavior of PDLA depending on the temperature. Bare silica nanoparticles increased the crystallization behavior of PDLA regardless of annealing temperature. In contrast, poly(ethylene glycol) (PEG) grafted silica nanoparticles increased the crystallization rate at 80 and 130 °C, but they decreased the crystallization rate at 120 °C. A possible reason was that PEG grafted silica nanoparticles acted as plasticizers while the bare silica nanoparticles acted as nucleating agents. © 2015 Society of Chemical Industry
Co-reporter:Lian-ying Wu;Lei Yu;Xiao-hui Fu;Zhi-bo Li 李志波
Chinese Journal of Polymer Science 2015 Volume 33( Issue 8) pp:1140-1149
Publication Date(Web):2015 August
DOI:10.1007/s10118-015-1640-0
A series of monomethoxy poly(ethylene glycol) (mPEG) grafted copolyglutamates (PmPEGs) were synthesized through ring-opening polymerization (ROP) followed by click chemistry. Supramolecular hydrogels based on polymer inclusion complexes (ICs) between PmPEG and α-cyclodextrin (α-CD) were prepared in aqueous solution. The rheological measurements indicated their gelation properties were affected by several factors including the mPEG length, graft density and the sample concentration. These hydrogels displayed thermo-sensitive gel-sol transition under appropriate conditions due to the reversible mPEG and α-CD inclusion complexation. These hydrogels also showed pH-sensitive behavior due to the deprotonate of carboxylic acid side groups. The ICs formation of a channel-type crystalline structure induced gelation mechanism was verified by various techniques. In vitro cytotoxicity assays demonstrated that the supramolecular hydrogels are nontoxic and cytocompatible.
Co-reporter:Yong Shen, Solenne Desseaux, Bethany Aden, Bradley S. Lokitz, S. Michael Kilbey II, Zhibo Li, and Harm-Anton Klok
Macromolecules 2015 Volume 48(Issue 8) pp:2399-2406
Publication Date(Web):April 20, 2015
DOI:10.1021/acs.macromol.5b00017
Surface-grafting thermoresponsive polymers allows the preparation of thin polymer brush coatings with surface properties that can be manipulated by variation of temperature. In most instances, thermoresponsive polymer brushes are produced using polymers that dehydrate and collapse above a certain temperature. This report presents the preparation and properties of polymer brushes that show thermoresponsive surface properties, yet are shape-persistent in that they do not undergo main chain collapse. The polymer brushes presented here are obtained via vapor deposition surface-initiated ring-opening polymerization (SI-ROP) of γ-di- or tri(ethylene glycol)-modified glutamic acid N-carboxyanhydrides. Vapor deposition SI-ROP of γ-di- or tri(ethylene glycol)-modified l- or d-glutamic acid N-carboxyanhydrides affords helical surface-tethered polymer chains that do not show any changes in secondary structure between 10 and 70 °C. QCM-D experiments, however, revealed significant dehydration of poly(γ-(2-(2-methoxyethoxy)ethyl)-l-glutamate) (poly(L-EG2-Glu)) brushes upon heating from 10 to 40 °C. At the same time, AFM and ellipsometry studies did not reveal significant variations in film thickness over this temperature range, which is consistent with the shape-persistent nature of these polypeptide brushes and indicates that the thermoresponsiveness of the films is primarily due to hydration and dehydration of the oligo(ethylene glycol) side chains. The results presented here illustrate the potential of surface-initiated NCA ring-opening polymerization to generate densely grafted assemblies of polymer chains that possess well-defined secondary structures and tunable surface properties. These polypeptide brushes complement their conformationally unordered counterparts that can be generated via surface-initiated polymerization of vinyl-type monomers and represent another step forward to biomimetic surfaces and interfaces.
Co-reporter:Xiaohui Fu;Yong Shen;Yinan Ma;Wenxin Fu
Science China Chemistry 2015 Volume 58( Issue 6) pp:1005-1012
Publication Date(Web):2015 June
DOI:10.1007/s11426-014-5297-2
A series of ABA triblock copolymers of poly(γ-(2-methoxy ethoxy)esteryl-glutamate)-block-poly(ethylene glycol)-block-poly(γ-(2-methoxy ethoxy)esteryl-glutamate) with poly(ethylene glycol) as middle hydrophilic B block and oligo(ethylene glycol)-functionalized polyglutamate (poly-L-EG2Glu) as terminal A blocks were prepared via ring-opening polymerization of EG2Glu N-carboxyanhydride (NCA). The resulting P(EG2Glu)-b-PEG-b-P(EG2Glu) triblocks can spontaneously form hydrogels in water. The intermolecular hydrogen bonding interactions between polypeptides blocks were responsible for the formation of gel network structure. These hydrogels displayed shear-thinning and rapid recovery properties, which endowed them potential application as injectable drug delivery system. The mechanical strength of hydrogels can be modulated by copolymer composition, molecular weight and concentrations. Also, it was found that the hydrogels’ strength decreased with temperature due to dehydration of polypeptide segments. Atomic force microscopy and scanning electron microscopy images revealed that these hydrogels were formed through micelle packing mechanism. Circular dichroism and Fourier transform infrared spectroscopy characterizations suggested the poly-L-EG2Glu block adopted mixed conformation. A preliminary assessment of drug release in vitro demonstrated the hydrogels can offer a sustained release of doxorubicin (DOX) and the release rate could be controlled by varying chemical composition.
Co-reporter:Shuang Xia, Zuoning Wang, Hong Chen, Wenxin Fu, Jianfeng Wang, Zhibo Li, and Lei Jiang
ACS Nano 2015 Volume 9(Issue 2) pp:2167
Publication Date(Web):January 27, 2015
DOI:10.1021/acsnano.5b00119
Natural nacre with superior mechanical property is generally attributed to the layered “brick-and-mortar” nanostructure. However, the role of nanograins on the hard aragonite platelets, which is so-called nanoasperity, is rarely addressed. Herein, we prepared silica platelets with aragonite-like nanoasperities via biomineralization strategy and investigated the effects of nanoasperity on the mechanical properties of resulting layered nanocomposites composed of roughened silica platelets and poly(vinyl alcohol). The tensile deformation behavior of the nanocomposites demonstrates that nanograins on silica platelets are responsive for strain hardening, improved strength, and toughness. The structure origin is attributed to the nanoasperity-controlled platelet sliding.Keywords: bioinspired materials; biomineralization; hierarchical structure; nacre; nanoasperities;
Co-reporter:Yaoming Wan, Zhihua Gan and Zhibo Li
Polymer Chemistry 2014 vol. 5(Issue 5) pp:1720-1727
Publication Date(Web):18 Oct 2013
DOI:10.1039/C3PY01281F
Poly(ethylene oxide)-block-poly(ε-caprolactone) (PEG-b-PCL) copolymers with three kinds of terminal functional groups (amino, carboxyl and methoxyl) at the hydrophilic block end were synthesized via sequential ring-opening polymerization (ROP). Their structures were characterized by GPC and 1H NMR. Micelles prepared from these copolymers showed different surface charge properties. The enzymatic degradation behaviour of these charged micelles in PBS (pH 7.0) was investigated using DLS, UV and TEM. BSA was used as a model protein to simulate the interactions between charged micelles and plasma components. It was found that micelles with different surface charges showed distinct degradation behaviour using lipase PS as the enzyme and different stability in the presence of BSA. Micelles with a neutral surface group showed a slow and partial degradation, while charged micelles showed a quick and complete degradation. We found that the nature of interactions between charged micelles and proteins was critical to the stability of polymeric micelles in vitro.
Co-reporter:Deyang Yu, Chunhui Luo, Wenxin Fu and Zhibo Li
Polymer Chemistry 2014 vol. 5(Issue 15) pp:4561-4568
Publication Date(Web):28 Apr 2014
DOI:10.1039/C4PY00480A
Five (meth)acrylamide derivatives containing alanine ester/amide residues were synthesized and then polymerized using RAFT polymerization. After polymerization and further treatment of the obtained polymers with excess radical initiators, we obtained a series of homopolymers with well-defined molecular weights and end groups. Depending on the structure of side-chain terminal groups, these alanine-containing homopolymers displayed thermal-responsive behaviors in water. Samples containing a methyl ester group, i.e., poly(MA-L-Ala-OMe) and poly(Ac-L-Ala-OMe), showed low critical solution temperature (LCST) behaviors. Replacing methyl ester with ethyl or isopropyl ester groups caused loss of thermal-responsive properties. However, replacing the isopropyl ester with isopropyl amide groups can regain thermal-responsive polymers such as poly(MA-L-Ala-iPA). We further studied the LCST behaviors of these three homopolymers with respect to the degree of polymerization (DP), concentration, salt concentration, and chirality of amino acids. It was found that the cloud point (CP) decreased with increasing polymer concentration, DP and salt concentration. The CPs of the polymers prepared from a pair of enantiomers showed no distinct difference, while the random copolymer of the two enantiomers displayed higher CP than optically pure homopolymers.
Co-reporter:Shusheng Zhang, Wenxin Fu and Zhibo Li
Polymer Chemistry 2014 vol. 5(Issue 10) pp:3346-3351
Publication Date(Web):24 Jan 2014
DOI:10.1039/C4PY00016A
A poly(ethylene glycol)-b-poly(γ-(2-methoxyethoxy)esteryl-L-glutamate) (PEG-b-poly-L-EG2Glu) diblock was prepared by the ring-opening polymerization (ROP) of L-EG2Glu N-carboxyanhydride (NCA) using PEG–NH2 as the macroinitiator. When the average degree of polymerization (DP) for poly-L-EG2Glu was below 40, the PEG-b-poly-L-EG2Glu diblock could spontaneously form hydrogels in water. For the different diblocks, a thermally-induced increase in mechanical strength was observed for the PEG-b-poly-L-EG2Glu diblock between 20–45 °C. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) revealed that continuous networks of nanoribbons were formed in these hydrogel samples. Circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) characterization suggested that the formation of sufficient β-sheet content accounted for the nanoribbon assemblies and hydrogel networks. The minimal gelation concentration and gel mechanical properties were found to strongly depend on the composition of the PEG-b-poly-L-EG2Glu diblocks.
Co-reporter:Yinan Ma, Xiaohui Fu, Yong Shen, Wenxin Fu, and Zhibo Li
Macromolecules 2014 Volume 47(Issue 14) pp:4684-4689
Publication Date(Web):July 14, 2014
DOI:10.1021/ma501104s
Three cysteine derivatives were synthesized in high yield by ligating monomethoxy oligo(ethylene glycol) (OEG) to l-cysteine thiol group using sulfenyl chlorides. These OEG groups containing di-, tri-, and tetra-EG units were linked with l-cysteine via disulfide bond. The three monomers were then converted into corresponding N-carboxyanhydrides (NCAs) using triphosgene in THF. Subsequent ring-opening polymerization (ROP) of disulfide bond containing NCAs gave three poly-EGx-l-cysteine derivatives. The obtained poly-EGx-l-cysteine with x = 3 and 4 displayed thermal-responsive behaviors in water, but the temperature-induced phase transition was found surprisingly irreversible. Such irreversible thermal-responsive behaviors were attributed to cross-linking arising from disulfide bonds exchanges. Using PEG-NH2 as macroinitiator, we also prepared two PEG-b-poly-EGx-l-cysteine diblocks, which could undergo irreversible thermal-induced sol–gel transition, which was caused by the disulfide bonds exchanging reactions. These hydrogels displayed partially shear-thinning and rapid recovery properties allowing new capabilities to construct stimuli-responsive injectable hydrogels in biomedical applications.
Co-reporter:Dr. Wenxin Fu;Kai Sun ;Dr. Zhibo Li
Chemistry – An Asian Journal 2014 Volume 9( Issue 8) pp:
Publication Date(Web):
DOI:10.1002/asia.201490029
Co-reporter:Dr. Wenxin Fu;Kai Sun ;Dr. Zhibo Li
Chemistry – An Asian Journal 2014 Volume 9( Issue 8) pp:
Publication Date(Web):
DOI:10.1002/asia.201402100
Abstract
Asymmetric and symmetric L-lysine N-carboxylic anhydrides based on perylene bisimide derivatives were successfully synthesized and grafted onto silicon wafers via surface-initiated ring-opening polymerization. The grafted n-type semiconductor film was flat and compact, and its thickness could be tuned by variation of the polymerization conditions.
Co-reporter:Jingjing Lai, Wenxin Fu, Lin Zhu, Ruohai Guo, Dehai Liang, Zhibo Li, and Yanbin Huang
Langmuir 2014 Volume 30(Issue 24) pp:7221-7226
Publication Date(Web):2017-2-22
DOI:10.1021/la501622t
Amyloid formation is now considered a universal and intrinsic property of all proteins, irrespective of their sequences. Therefore, it is interesting to see whether random copolymers of amino acids can also form amyloid aggregates. Here we use a copolymer of 4 amino acids, mimicking the clinically used drug Glatiramer, and demonstrate that it does form amyloid-like fibrils in the aqueous solution despite its random sequence structure. The fibrillar aggregates show an alanine-rich β-sheet secondary structure, proving the high tolerance of amyloid aggregates to the sequence irregularity in poly(amino acid)s, and suggesting the potential application of random copolymers as amyloid materials.
Co-reporter:Yan Sun, Wenxin Fu, Zhibo Li, and Zhaohui Wang
Langmuir 2014 Volume 30(Issue 28) pp:8615-8620
Publication Date(Web):2017-2-22
DOI:10.1021/la502222d
The enhanced dispersing capability of these bolaamphiphiles can be attributed to the large aromatic perylene core. The aqueous dispersion efficiency of single-walled carbon nanotubes (SWCNTs) is investigated by UV–vis absorption, fluorescence emission and Raman spectra, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. It is found that the tetrachloroperylene backbone moieties could interact with SWCNT via synergistic π–π and hydrophobic interactions, and the dispersing properties are closely related to the hydrophilic part of bolaamphiles. This study not only demonstrates tetrachloroperylene derivatives are able to stabilize SWCNTs, but also provides the possibility to understand the structure–property relationship between SWCNTs and tetrachloroperylene-based surfactants.
Co-reporter:Kai Sun, Chengyi Xiao, Chunming Liu, Wenxin Fu, Zhaohui Wang, and Zhibo Li
Langmuir 2014 Volume 30(Issue 37) pp:11040-11045
Publication Date(Web):2017-2-22
DOI:10.1021/la502532g
Chiral supramolecular structures are becoming increasingly attractive for their specific molecular arrangements, exceptional properties, and promising applications in chiral sensing and separation. However, constructing responsive chiral supramolecular structures remains a great challenge. Here, glucose-functionalized tetrachloro-perylene bisimides (GTPBIs) with thermally sensitive self-assembly behaviors are designed and synthesized. In a methanol/water mixture, GTPBIs self-assembled into twisted ribbons and microplates at 4 and 25 °C, respectively. Furthermore, the ribbon structure was metastable and could transform into microplates when the temperature was increased from 4 to 25 °C. Transmission electron microscopy (TEM) was used to track the evolution of morphology and study the assembly mechanisms of correponding nanostructures at different time intervals. The supramolecular structures were characterized with various techniques, including circular dichroism, TEM, scanning electron microscopy, atomic force microscopy, ultraviolet–visible absorption, and fluorescence spectra. This study provides insight into controlling molecular parameters and assembly conditions to construct chiral supramolecular structures.
Co-reporter:Xiaohui Fu, Yinan Ma, Yong Shen, Wenxin Fu, and Zhibo Li
Biomacromolecules 2014 Volume 15(Issue 3) pp:
Publication Date(Web):February 14, 2014
DOI:10.1021/bm5000554
The oxidation-responsive behaviors of OEGylated poly-l-cysteine homopolypeptides, that is, poly(l-EGxMA-C)n, were investigated. These poly-l-cysteine derivatives adopted mixed conformation in water, in which the β-sheet accounted for a significant proportion. Upon oxidation, the thioethers in polypeptide side chains were converted to polar sulfone groups, which triggered the secondary structure transition from β-sheet preferred conformation to random coil. Accordingly, the increase of side-chain polarity together with conformation changes increased samples’ water solubility and cloud point temperature. Using mPEG45-NH2 as macroinitiator, we synthesized PEG45-b-poly(l-EG2MA-C)22 diblock copolymer via ring-opening polymerization (ROP) of l-EG2MA-C N-carboxyanhydride (NCA). The PEG45-b-poly(l-EG2MA-C)22 was able to self-assemble into spherical micelles in aqueous solution, and the micelles could undergo an oxidation-triggered disassembly due to the oxidation-responsive thioethers. Such a new class of oxidation-responsive polypeptides might provide a promising platform to construct inflammation targeting drug delivery systems.
Co-reporter:Hong Chen, Lin Xia, Wenxin Fu, Zhenzhong Yang and Zhibo Li
Chemical Communications 2013 vol. 49(Issue 13) pp:1300-1302
Publication Date(Web):20 Dec 2012
DOI:10.1039/C2CC38293H
We report the biomimetic synthesis of polyethylene glycol (PEG) grafted silica nanoplates templated by double hydrophilic PEG-b-poly-L-lysine diblock copolymers. The silica nanoplates can be re-dispersed in PEG selective solvents. The sizes of silica nanoplates can be tuned from a few hundred nanometers to tens of micrometers.
Co-reporter:Junyang Shen, Chongyi Chen, Wenxin Fu, Linqi Shi, and Zhibo Li
Langmuir 2013 Volume 29(Issue 21) pp:6271-6278
Publication Date(Web):May 1, 2013
DOI:10.1021/la401095s
Poly(ethylene glycol)-block-poly(γ-(2-methoxyethoxy)esteryl-l-glutamate) (PEG-b-poly-l-EG2Glu) was synthesized via ring-opening polymerization (ROP) of l-EG2Glu N-carboxyanhydride (NCA) using PEG-NH2 as macroinitiator. This diblock contained a thermo-responsive poly-l-EG2Glu block, which adopted primarily helical conformation in pristine aqueous solution. We found that PEG-b-poly-l-EG2Glu diblock can display two levels of self-assembly behaviors associated with hydrophobic interactions and conformation-specific reassembly, respectively. Upon temperature increase, the PEG-b-poly-l-EG2Glu diblock formed wormlike micelles, in which the poly-l-EG2Glu formed the micelle core and maintained helical conformation. However, extension of thermal annealing time drove the secondary structure transformation of the poly-l-EG2Glu block from helical conformation to β-sheet, which accounted for an assembly structure transition from wormlike micelles to nanoribbons. The critical factor was that poly-l-EG2Glu block can undergo thermo-induced hydrophobicity and conformation transformation, which offered an additional parameter to tune the nature of molecular interactions, i.e., intermolecular versus intramolecular hydrogen bonding interactions. The corresponding conformation and assembly structure changes were characterized using FTIR and electron microscopy, respectively.
Co-reporter:Chongyi Chen, Decheng Wu, Wenxin Fu, and Zhibo Li
Biomacromolecules 2013 Volume 14(Issue 8) pp:
Publication Date(Web):July 4, 2013
DOI:10.1021/bm4008259
Three alkyl-polypeptide (AP) amphiphiles were prepared using ring-opening polymerization of α-amino acid N-carboxyanhydride. The polypeptide segment was composed of diethylene-glycol-monomethyl-ether-functionalized poly-l-glutamate (poly-l-EG2Glu). These AP amphiphiles can spontaneously self-assemble into transparent hydrogels in water. These hydrogels showed shear thinning properties, and their strength can be modulated by hydrophobic alkyl tails. CryoTEM and AFM characterizations suggested that these hydrogels were formed by nanoribbons arising from intermolecular interactions between nonionic poly-l-EG2Glu segments.
Co-reporter:Shusheng Zhang
Journal of Polymer Science Part B: Polymer Physics 2013 Volume 51( Issue 7) pp:546-555
Publication Date(Web):
DOI:10.1002/polb.23263
Abstract
Design and synthesis of biodegradable stimuli-responsive polypeptides are important areas considering their promising applications in biomedical fields. This article summarizes the most recent progresses in the development of stimuli-responsive polypeptide materials prepared via ring-opening polymerization of α-amino acid N-carboxyanhydrides. We discuss the design, synthesis and structure-property correlation of emerging materials including thermo-responsive, redox-responsive, photo-responsive and biomolecule responsive polypeptides. Considering the unique structural features of amino acids, we try to emphasize that the thermo-responsive properties not only depend on the amino acid structure but also rely on the secondary structures of polypeptides. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
Co-reporter:Xiaohui Fu, Yong Shen, Wenxin Fu, and Zhibo Li
Macromolecules 2013 Volume 46(Issue 10) pp:3753-3760
Publication Date(Web):April 30, 2013
DOI:10.1021/ma400678w
A series of new functional amino acids were prepared in high yield via thiol–ene Michael addition between l-cysteine and monomethoxy oligo(ethylene glycol) (OEG) functionalized methacrylates (OEGxMA) and acrylate (OEGxA). These OEGylated cysteine derivatives were converted into polymerizable N-carboxyanhydride (NCA) monomers using triphosgene. Subsequent ring-opening polymerization (ROP) of these NCA monomers gave a series of OEGylated poly-l-cysteine (poly-EGxMA-C or poly-EGxA-C) homopolypeptides. Depending on the length of OEG side chains, poly-EGxMA-C and poly-EGxA-C polypeptides displayed different solubility and secondary structure in water. More importantly, the obtained polypeptides can display reversible thermoresponsive properties in water when the x value is between 3 and 5. The synthetic strategy represents a highly efficient method to prepare nonionic functional polypeptides with tunable thermoresponsive properties.
Co-reporter:Yuchun Han, Wentao Wang, Yongqiang Tang, Shusheng Zhang, Zhibo Li, and Yilin Wang
Langmuir 2013 Volume 29(Issue 30) pp:9316-9323
Publication Date(Web):July 8, 2013
DOI:10.1021/la4019713
The coassembly of poly(ethylene glycol)-b-poly(glutamate sodium) copolymer (PEG113-PGlu100) with cationic gemini surfactants alkanediyl-α,ω-bis-(dodecyldimethylammonium bromide) [C12H25(CH3)2N(CH2)SN(CH3)2C12H25]Br2 (designated as C12CSC12Br2, S = 3, 6, and 12) have been studied by isothermal titration microcalorimetry, cryogenic transmission electron microscopy, circular dichroism, small-angle X-ray scattering, zeta potential, and size measurement. It has been shown that the electrostatic interaction of C12CSC12Br2 with the anionic carboxylate groups of PEG113-PGlu100 leads to complexation, and the C12CSC12Br2/PEG113-PGlu100 complexes are soluble even at the electroneutral point. The complexes display the feature of superamphiphiles and assemble into ordered nanosheets with a sandwich-like packing. The gemini molecules which were already bound with PGlu chains associate through hydrophobic interaction and constitute the middle part of the nanosheets, whereas the top and bottom of the nanosheets are hydrophilic PEG chains. The size and morphology of the nanosheets are affected by the spacer length of the gemini surfactants. The average sizes of the aggregates at the electroneutral point are 81, 68, and 90 nm for C12C3C12Br2/PEG113-PGlu100, C12C6C12Br2/PEG113-PGlu100, and C12C12C12Br2/PEG113-PGlu100, respectively. Both C12C3C12Br2/PEG113-PGlu100 and C12C12C12Br2/PEG113-PGlu100 mainly generate hexagonal nanosheets, while the C12C6C12Br2/PEG113-PGlu100 system only induces round nanosheets.
Co-reporter:Shusheng Zhang;Chongyi Chen 李志波
Chinese Journal of Polymer Science 2013 Volume 31( Issue 2) pp:201-210
Publication Date(Web):2013 February
DOI:10.1007/s10118-013-1218-7
We investigated the ring opening polymerization (ROP) of di- and tri-ethylene glycol monomethyl ether functionalized L-glutamate N-carboxyanhydrides (NCAs) using hexamethyldisilazane (HMDS) as primary initiator and 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD) as co-initiator. The binary initiator system afforded a living ROP for these pegylated NCAs, and a series of homopolypeptides with controlled molecular weight (MW) and low polydispersity were obtained. We then systematically studied the helical content and clouding point (CP) dependence on polypeptide MW using circular dichroism (CD) spectroscopy and turbidity measurements, respectively. We found that the helical content of both homopolypeptides increased with MW, but the triethylene glycol functionalized poly-L-glutamate (poly-L-EG3Glu) intended to form more stable α-helical structure than diethylene glycol functionalized counterpart (poly-L-EG2Glu) at similar MW. Accordingly, the CP of poly-L-EG2Glu with known end group has strong dependence on its helical content, which is essentially determined by MW. Our results suggested that the thermal responsive properties of these unique pegylated poly-L-glutamates not only rely on their chemical structure but also on their secondary structures, which is different from conventional thermal responsive polymers.
Co-reporter:Yong Shen;Yinan Ma
Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 3) pp:708-715
Publication Date(Web):
DOI:10.1002/pola.26429
Abstract
We report a highly efficient approach to prepare dendrimers by taking advantage of the orthogonal characteristic of aza-Michael addition and thiol-yne reactions. A fifth generation dendrimer was synthesized within five steps without protection/activation procedures. The reactions proceed under benign conditions without byproducts, and the target products can be easily purified via extraction or precipitation without chromatography. The structure of each generation dendrimer was characterized using NMR spectroscopy, size exclusion chromatography, and mass spectrometry. The obtained dendrimers can have peripheral amine or alkyne groups. We demonstrated that these groups can be used for selective and specific conjugation with various functional groups. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Co-reporter:Aifeng Lv;Sreenivasa R. Puniredd;Jiahui Zhang;Hongfei Zhu;Wei Jiang;Huanli Dong;Yudong He;Lang Jiang;Yan Li;Wojciech Pisula;Qing Meng;Wenping Hu;Zhaohui Wang
Advanced Materials 2012 Volume 24( Issue 19) pp:2626-2630
Publication Date(Web):
DOI:10.1002/adma.201104987
Co-reporter:Wenting Zheng ; Jie Gao ; Lijie Song ; Chongyi Chen ; Di Guan ; Zhihong Wang ; Zhibo Li ; Deling Kong ;Zhimou Yang
Journal of the American Chemical Society 2012 Volume 135(Issue 1) pp:266-271
Publication Date(Web):December 14, 2012
DOI:10.1021/ja308690y
We demonstrate that a tripeptide hydrogelator, Nap-FFG, can selectively self-assemble at the surface of platelets, thus inhibiting ADP-, collagen-, thrombin- and arachidonic acid (AA)-induced human platelet aggregations with the IC50 values of 0.035 (41), 0.14 (162), 0.062 (68), and 0.13 mg/mL (148 μM), respectively. Other tripeptide hydrogelators with chemical structures of Nap-FFX (X = A, K, S, or E) could not or possessed less potencies to inhibit platelet aggregations. We observed higher amounts of Nap-FFG at the platelet surface by the techniques of LC-MS and confocal microscopy. We also observed self-assembled nanofibers around the platelet incubated with the Nap-FFG by cryo-TEM. The ζ potential of Nap-FFG treated platelets was a little bit more negative than that of untreated ones. The amount of Nap-FFG at the surface of NIH 3T3 cells was much less than that of platelets. These observations suggested that Nap-FFG could selectively self-assemble through unknown ligand–receptor interactions and form thin layers of hydrogels at the surface of platelets, thus preventing the aggregation of them. This study not only broadened the application and opened up a new door for biomedical applications of molecular hydrogels but also might provide a novel strategy to counteract infection diseases through selective surface-induced hydrogelations at pathogens, such as bacteria and virus.
Co-reporter:Yan Sun, Zhibo Li and Zhaohui Wang
Journal of Materials Chemistry A 2012 vol. 22(Issue 10) pp:4312-4318
Publication Date(Web):05 Dec 2011
DOI:10.1039/C1JM14521E
L-Lysine functionalized tetrachloroperylene bisimide (Lys-4ClPBI-Lys) was synthesized, and its aqueous self-assembly behaviours were investigated at different pH values. The zwitterionic-type Lys-4ClPBI-Lys amphiphile spontaneously self-assembled into a uniform monolayer film in water at pH ranging from 9 to 1, whereas it did not formed any ordered aggregates in solution with pH above 10. Formation of the monolayer film was believed due to synergistic interaction of directional π–π interactions and intermolecular hydrogen bonding. In contrast, the addition of copper(II) ions induced the formation of multilayer films due to inter-film ligation between Cu2+ and the α-amino acid moiety. The corresponding self-assembly behaviours and assemblies' structures were characterized using UV-vis absorption and fluorescence emission spectroscopy, cryogenic transmission electron microscopy, atomic force microscopy, and X-ray diffraction.
Co-reporter:Yu Liu;Ping Chen
Macromolecular Rapid Communications 2012 Volume 33( Issue 4) pp:287-295
Publication Date(Web):
DOI:10.1002/marc.201100649
Abstract
A new type of molecular bottlebrush with poly-L-lysine (PLL) as backbone was synthesized via ROP followed by ATRP. A Nϵ-bromoisobutyryl functionalized Nα-CBZ-L-lysine was firstly synthesized and converted in polymerizable α-amino acid N-carboxyanhydride (NCA), which was then polymerized using Ni(0) transition metal complex to give well-defined bromo-functionalized homopolypeptide (PBrLL), from which we prepared two types of polypeptide bottlebrushes with polystyrene and poly(oligoethylene glycol methacrylate) as side-chains. PBrLL macroinitiator was demonstrated to have high initiation efficiency for ATRP, which allowed good control over side-chain length. CD and FTIR characterization revealed that both PBrLL macroinitiator and PLL backbone of bottlebrushes adopted α-helical conformation in appropriate solvents.
Co-reporter:Chunhui Luo, Yu Liu and Zhibo Li
Soft Matter 2012 vol. 8(Issue 9) pp:2618-2626
Publication Date(Web):20 Jan 2012
DOI:10.1039/C2SM07063D
A poly(ethylene glycol)-b-poly(n-butyl methacrylate)-b-poly(N,N′-dimethylamino ethyl methacrylate) (PEG-b-PnBMA-b-PDMAEMA) triblcok terpolymer with a dual pH- and thermo-responsive PDMAEMA as end segment was prepared via sequential RAFT polymerization. The PEG-b-PnBMA-b-PDMAEMA self-assembled into spherical micelles in acidic solution but transformed into cylindrical micelles in alkaline solution. This pH induced re-assembly was reversible. Moreover, we found that this terpolymer underwent a pathway dependent re-assembly from cylinder to toroid or to vesicle upon programmed variation of solution pH and temperature in dilute aqueous solution. Using dynamic light scattering (DLS) and cryogenic transmission electron microscopy (cryoTEM), we found that this stimuli-induced re-assembly from cylinder to toroid or to vesicle was apparently irreversible, and restoration of pristine morphology only happened using different external stimulus. Our studies demonstrated a prototype of smart supramolecular assembly that we can re-assembly into different micelle morphologies using different stimuli.
Co-reporter:Chunhui Luo, Bin Zhao, Zhibo Li
Polymer 2012 Volume 53(Issue 8) pp:1725-1732
Publication Date(Web):3 April 2012
DOI:10.1016/j.polymer.2012.02.032
Four kinds of well defined poly(N-methacryloyl-L-amino acid)s were prepared via reversible addition fragmentation chain transfer polymerization. The effects of molecular structure, molecular weight, and end-group on their responsive properties in water were investigated. We found that the monomer structure is critical for the polymer to exhibit stimuli-responsive properties in water; only polymers derived from aspartic acid showed defined dual thermo- and pH-responsive properties. To study the effects of molecular weight and end group on the lower critical solution temperature behavior of poly(N-methacryloyl-L-β-isopropyl aspartic acid) (PMAIPAC), a series of PMAIPAC homopolymers with controlled molecular weights and narrow polydispersities were prepared and treated with excess radical initiators to give defined end groups. The cloud point of PMAIPAC was found to increase with the increase of solution pH, due to the ionization of carboxylic acid groups, and decrease with the increase of molecular weight. The structure of end groups also affects the cloud point of PMAIPAC particularly for low molecular weight samples at low pH.
Co-reporter:Yuchun Han, Lin Xia, Linyi Zhu, Shusheng Zhang, Zhibo Li, and Yilin Wang
Langmuir 2012 Volume 28(Issue 43) pp:15134-15140
Publication Date(Web):October 11, 2012
DOI:10.1021/la303646r
The association behaviors of single-chain surfactant dodecyltrimethylammonium bromide (DTAB) with double hydrophilic block co-polymers poly(ethylene glycol)-b-poly(sodium glutamate) (PEG113–PGlu50 or PEG113–PGlu100) were investigated using isothermal titration microcalorimetry, cryogenic transmission electron microscopy, circular dichroism, ζ potential, and particle size measurements. The electrostatic interaction between DTAB and the oppositely charged carboxylate groups of PEG–PGlu induces the formation of super-amphiphiles, which further self-assemble into ordered aggregates. Dependent upon the charge ratios between DTAB and the glutamic acid residue of the co-polymer, the mixture solutions can change from transparent to opalescent without precipitation. Dependent upon the chain length of the PGlu block, the mixture of DTAB and PEG–PGlu diblocks can form two different aggregates at their corresponding electroneutral point. Spherical and rod-like aggregates are formed in the PEG113–PGlu50/DTAB mixture, while the vesicular aggregates are observed in the PEG113–PGlu100/DTAB mixture solution. Because the PEG113–PGlu100/DTAB super-amphiphile has more hydrophobic components than that of the PEG113–PGlu50/DTAB super-amphiphile, the former prefers forming the ordered aggregates with higher curvature, such as spherical and rod aggregates, but the latter prefers forming vesicular aggregates with lower curvature.
Co-reporter:Wenxin Fu;Chang He
Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 7) pp:1333-1341
Publication Date(Web):
DOI:10.1002/pola.25899
Abstract
Polymerizable tetrachloro-perylenediimdes containing endo/exo-norbornene groups on both imide sides were designed and synthesized. Endo/Exo-type soluble ladder-like polynorbornenes with perylenediimide (PDI) as bridges were prepared by ring-opening metathesis polymerization (ROMP). XRD characterizations showed that the ladder-like polynorbornenes had ordered structures similar to the supramolecular precursors assembled from the corresponding monomers. TGA measurements demonstrated great thermal stabilities for the both target P1-Endo and P2-Exo with Td of about 320 °C at 5 wt % loss, respectively, which is important for further application in devices. Both polymers have good solubility in common organic solvents and easy to form thin films. Photophysical studies and cyclic voltammetry investigations reveal that polynorbornene films have wide-range absorption from 400 nm to 600 nm and the HOMO/LUMO energy levels could be matched well with the donor-PCzTh-TVDCN. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Co-reporter:Ping Chen, Chuang Li, Dongsheng Liu, and Zhibo Li
Macromolecules 2012 Volume 45(Issue 24) pp:9579-9584
Publication Date(Web):December 6, 2012
DOI:10.1021/ma302233m
A new type of DNA grafted polypeptide molecular brush was synthesized via a combination of ring-opening polymerization (ROP) and click chemistry. This conjugation method provides an easy and efficient approach to obtain a hybrid DNA-grafted polypeptide molecular bottlebrush. The structure and assembly behaviors of this hybrid brush were investigated using electrophoresis, UV–vis spectroscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM). Hierarchical supramolecular assemblies can be obtained through hybridization of two kinds of polypeptide-g-DNA molecular bottlebrushes containing complementary DNA side chains. We further demonstrated that such polypeptide-g-DNA can be hybridized with ds-DNA and DNA-grafted gold nanoparticles to form a supermolecular bottlebrush and hybrid bottlebrush, respectively. In addition, DNA-polypeptide hydrogel can be prepared by hybridization of polypeptide-g-DNA with a linker-ds-DNA, which contains the complementary “sticky ends” to serve as cross-linkers.
Co-reporter:Wenxin Fu, Chang He, Shidong Jiang, Zhize Chen, Jintao Zhang, Zhibo Li, Shouke Yan, and Rongben Zhang
Macromolecules 2011 Volume 44(Issue 2) pp:203-207
Publication Date(Web):December 28, 2010
DOI:10.1021/ma1025797
A soluble perylenediimide (PDI) bridged ladder polysiloxane (PDI-LPS) was prepared using ladder superstructure (LS) directed dehydration polycondensation. LS was first assembled via synergistic interactions of hydrogen-bonding and π−π stacking of tetrasilanol monomers (M2s) as verified from XRD, 29Si NMR, and VPO characterizations. The ladder regularity of PDI-LPS was confirmed by a narrow half-peak width (Δ) of <1 ppm for SiO2/2 unit in the 29Si NMR spectra. The alignment of ladder chains was also demonstrated from high-resolution transmission electronic microscopy (HR-TEM) observations. We successfully used ladderlike structure to chemically confine PDI cores within one-dimensional polymeric semiconductor. The resulting PDI-LPS not only retained PDI’s optoelectronic properties but also gained enhanced solubility in common organic solvents and improved thermal stability.
Co-reporter:Lin Xia and Zhibo Li
Langmuir 2011 Volume 27(Issue 3) pp:1116-1122
Publication Date(Web):December 28, 2010
DOI:10.1021/la104030f
Two poly(l-lysine·HBr) (PLL) homopolypeptides along with phosphate buffer were used as organic templates to direct biomimetic silica synthesis under ambient conditions. We found that mixing sequence of reaction species played a key role in terms of controlling resulting silica morphologies. Premixing PLL solution with phosphate buffer followed with addition of silicic acid produced regular hexagonal silica plates, while premixing silicic acid with either PLL or phosphate solution prior to adding phosphate buffer or PLL solution only produced irregular silica nanoparticles. In addition, we found that the concentration of phosphate ions was also an important factor to control silica structures. When the ratio of phosphate/lysine residue (δ) was smaller than one, PLL only produced irregular silica particles. When δ was larger than 2.5, PLL produced regular silica plates. We performed CD measurements to track the conformation transition of PLL during biomineralization process and found that the resulting silica structures were closely related to the secondary structure of PLL regardless of experimental conditions. Only when PLL underwent an in situ coil−helix transition could ordered silica structures be produced.
Co-reporter:Yan Sun, Chang He, Kai Sun, Yan Li, Huanli Dong, Zhaohui Wang, and Zhibo Li
Langmuir 2011 Volume 27(Issue 18) pp:11364-11371
Publication Date(Web):August 8, 2011
DOI:10.1021/la202107r
Controllable nanostructures with tunable dimensions were obtained via self-assembly of CBZ-l-lysine-functionalized tetrachloroperylene bisimides (4ClPBI-Lys). Depending on the nature of substitute, solvent polarity, and sample concentration, 4ClPBI-Lys could form nanosphere, nanowire, nanobelt, and nanosheet, which were found to have different degree of molecular ordering. The effects of substitution position with respect to l-lysine on 4ClPBI were also explored in terms of assembly nanostructures. Hydrogen bonding was important to promote formation of long-range ordering. The nanostructures of different assemblies were characterized using SEM, TEM, XRD, UV–vis, and FTIR spectroscopy. For each obtained supramolecular assembly, we also found that the molecular packing motif ultimately determined the corresponding devices’ electronic properties.
Co-reporter:Chongyi Chen, Zhaohui Wang, and Zhibo Li
Biomacromolecules 2011 Volume 12(Issue 8) pp:
Publication Date(Web):June 30, 2011
DOI:10.1021/bm200849m
The synthesis and characterization of new thermoresponsive pegylated poly-l-glutamate (poly-l-EGxGlu) are described. The obtained polypeptides display low critical solution temperature (LCST) behaviors in water, and the LCST can be tuned via copolymerization of different amino acid monomers at varied molar ratio. This is the first example of thermoresponsive polypeptide made from ring-opening polymerization of α-amino acid N-carboxyanhydrides (NCAs). Circular dichroism characterizations reveal that the secondary structure of poly-l-EGxGlu depended on the chain length of the side chain.
Co-reporter:Lin Xia;Yu Liu
Macromolecular Bioscience 2010 Volume 10( Issue 12) pp:1566-1575
Publication Date(Web):
DOI:10.1002/mabi.201000297
Co-reporter:Yuchun Han, Chengqian He, Meiwen Cao, Xu Huang, Yilin Wang and Zhibo Li
Langmuir 2010 Volume 26(Issue 3) pp:1583-1587
Publication Date(Web):December 11, 2009
DOI:10.1021/la9042974
The accumulation of a peptide of 38−43 amino acids, in the form of fibrillar plaques, was one of the essential reasons for Alzheimer’s disease (AD). Discovering an agent that is able to disassemble and clear disease-associated Aβ peptide fibrils from the brains of AD patients would have critical implications not only in understanding the dynamic process of peptide aggregation but also in the development of therapeutic strategies for AD. This study reported a new finding that cationic gemini surfactant C12C6C12Br2 micelles can effectively disassemble the Aβ(1−40) fibrils in vitro. Systematic comparisons with other surfactants using ThT fluorescence, AFM, and FTIR techniques suggested that the disassembly effectiveness of gemini surfactant micelles arises from their special molecular structure (i.e., positively bicharged head and twin hydrophobic chains). To track the disassembly process, systematic cryoTEM characterization was also done, which suggested a three-stage disassembly process: (i) Spherical micelles are first absorbed onto the Aβ fibrils because of attractive electrostatic interaction. (ii) Elongated fibrils then disintegrate into short pieces and form nanoscopic aggregates via synergistic hydrophobic and electrostatic interactions. (iii) Finally, complete disaggregation of fibrils and dynamic reassembly result in the formation of peptide/surfactant complexes.
Co-reporter:Chunhui Luo, Yu Liu, and Zhibo Li
Macromolecules 2010 Volume 43(Issue 19) pp:8101-8108
Publication Date(Web):September 17, 2010
DOI:10.1021/ma1015227
A new type of thermo- and pH-responsive homopolymer was synthesized using reversible addition−fragmentation chain transfer (RAFT) polymerization. A novel functional methacrylamide monomer bearing α-aspartic acid derivative in the side chain, i.e., N-methacryloyl-l-β-isopropylasparagine benzyl ester (MA-iAsn-OBen), was first synthesized. Three poly(N-methacryloyl-l-β-isopropylasparagine benzyl ester)s [poly(MA-iAsn-OBen)] with controllable molecular weight and narrow molecular weight distribution were then prepared using RAFT polymerization. Selective removal of benzyl groups produced poly(N-methacryloyl-l-β-isopropylasparagine) [poly(MA-iAsn-OH)], which displayed a reversible lower critical solution temperature (LCST) in water. In addition, the LCST can be adjusted from 29 to 60 °C by changing solution pH values, salt concentrations, and polymer molecular weights. Using macromolecular chain transfer agent and RAFT polymerization, we prepared well-defined amphiphilic mPEG45-b-poly(MA-iAsn-OBen)53 diblock copolymer and double hydrophilic block copolymer [mPEG45-b-poly(MA-iAsn-OH)53]. The latter showed a thermo-induced self-assembly in water due to collapse of poly(MA-iAsn-OH) segment. We found that mPEG45-b-poly(MA-iAsn-OH)53 was soluble at room temperature while formed vesicles above the LCST of poly(MA-iAsn-OH)53.
Co-reporter:Jintao Zhang;Zhize Chen;Wenxin Fu;Ping Xie;Shouke Yan;Rongben Zhang
Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 11) pp:2491-2497
Publication Date(Web):
DOI:10.1002/pola.24021
Abstract
A soluble well-defined 9,10-diphenylanthryl-bridged ladder polysiloxane (DPAnLP) was prepared via supramolecular assembly-directed condensation polymerization of silanols. The ladder superstructure (LS) was obtained via a synergistic interaction of H-bonding and π–π stacking between polymerizable precursor 2-tert-butyl-9,10-bis(methyldihydroxylsilyl)anthracene in organic solvent. The resultant LS was then used as template to direct the condensation of silanol groups to obtain DPAnLP with high regularity. It was found that DPAnLP can emit blue light (430 nm) with great stability and high efficiency in both solution and solid film, which indicated a well organizing of fluorophore within confined environment (ladder structure). TGA and DSC measurements showed that DPAnLP had good thermal stability, and cyclic voltammetry detection gave a low-lying highest occupied molecular orbital level. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2491–2497, 2010
Co-reporter:Yan Sun, Zhibo Li and Zhaohui Wang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 10) pp:
Publication Date(Web):
DOI:10.1039/C1JM14521E
Co-reporter:Hong Chen, Lin Xia, Wenxin Fu, Zhenzhong Yang and Zhibo Li
Chemical Communications 2013 - vol. 49(Issue 13) pp:NaN1302-1302
Publication Date(Web):2012/12/20
DOI:10.1039/C2CC38293H
We report the biomimetic synthesis of polyethylene glycol (PEG) grafted silica nanoplates templated by double hydrophilic PEG-b-poly-L-lysine diblock copolymers. The silica nanoplates can be re-dispersed in PEG selective solvents. The sizes of silica nanoplates can be tuned from a few hundred nanometers to tens of micrometers.
Co-reporter:Yong Shen, Xiaohui Fu, Wenxin Fu and Zhibo Li
Chemical Society Reviews 2015 - vol. 44(Issue 3) pp:NaN622-622
Publication Date(Web):2014/10/22
DOI:10.1039/C4CS00271G
The stimuli-responsive polypeptides have drawn extensive attention because of their promising applications in biotechnology considering their biocompatibility, biodegradability, and bioactivity. In this tutorial review, we summarize the most recent progress in this area, including thermo-, redox-, photo-, and biomolecule responsive polypeptides over the past decade. The design and synthesis of stimuli-responsive polypeptides will be briefly introduced. The correlation between the structure and properties, particularly the effects of polypeptide conformation, will be emphasized here. In addition, the applications of stimuli-responsive polypeptides in controlled drug release and tissue engineering are briefly discussed.
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![Propanoic acid, 2-[[(ethylthio)thioxomethyl]thio]-2-methyl-](/data/chemimg/113500/881037-62-3.png)
![Propanoic acid, 2-[[(ethylthio)thioxomethyl]thio]-2-methyl-](/data/chemimg/113500/881037-62-3_b.png)
![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4.png)
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