ISSN 1000-3304CN 11-1857/O6

2018(1)

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2018, No.(1) Contents
2018, (1).
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2018, (1): 0-0.
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Feature Articles
Studies on Polypeptoid and Its Structure-Property Relationship
Sun Jing, Li Zhi-bo
2018, (1): 1-8. doi: 10.11777/j.issn1000-3304.2018.17220
[Abstract](1895) [FullText HTML] (807) [PDF 11715KB](152)
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Polypeptoids, also referred as poly(N-substituted glycines), are an emerging class of bioinspired polymers with excellent biocompatibility and potent biological activities. The polypeptoid has identical backbone compared to that of the polypeptide. Unlike the polypeptide, the side chain of the polypeptoid is covalently attached to the amide nitrogen instead of α-carbon in the main chain. It thus removes inter-and intra-chain hydrogen bonding in the backbone and also eliminates the main chain chirality, which results in substantial backbone flexibility. This allows for good solubility in many common solvents and accessible thermal processibility. In addition, the properties of polypeptoids are dominated by the side chain identity and physical-chemical properties, which enables the polypeptoids highly designable. By careful engineering and design of the side-chain structure, the secondary conformation, thermal property and degradability of the polypeptoids can be finely tuned. All these advantages make polypeptoids promising candidates for potential applications in nanoscience and biomedicine. The polypeptoid can be prepared by two distinct synthetic techniques that offer access to two material sub-classes. A two-step submonomer synthetic method that excludes main chain protecting groups has been developed based on the solid-phase peptide synthesis (SPPS). This approach enables precision structural control and near absolute monodispersity of the polymers. A classical polymerization approach can achieve high molecular weight of the polypeptoids. The combination of solid-phase synthesis with polymerization technique offers great opportunities to tailor structural design and to systematically investigate the relationship between structure and property of the polymers. It enables the preparation of next generation of bio-inspired polymeric materials with advanced functional properties. In this article, we discuss recent developments of the microphase separation and self-assembling behavior of the polypeptoids. We focus on the approach to systematically study the relationship of chemical structure and self-assembly behavior by finely tuning the side-chain structure of the polypeptoids, and to further obtain the novel biopolymers with extraordinary microphase separation behavior and self-assembling nanostructures. The potential applications in biomedicine and energy storage are also discussed.
Short Peptide-based Hydrogels: Mild Preparation Methods and Their Application as Vaccine Adjuvant
Wang You-zhi, Gao Jie, Yang Zhi-mou
2018, (1): 9-20. doi: 10.11777/j.issn1000-3304.2018.17199
[Abstract](1657) [FullText HTML] (653) [PDF 24681KB](105)
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Self-assembly prevails in nature, and has been used as a powerful strategy for construction of functional materials. Small molecular hydrogel is composed of nanofibers formed by self-assembly of small molecules (molecular weight usually < 2000) in aqueous solution. Among them, hydrogels formed by the self-assembly of short peptides through noncovalent interaction have attracted intensive interests due to their ease of design, biocompatibility and biodegradability, as well as fast response to external environment. Several classical methods have been developed to construct peptide-based hydrogels, including heating-cooling cycle, pH value adjustment, ionic strength change, solvent transform and sonication induction. However, these methods were not suitable for the encapsulation of bioactive components such as proteins and cells. Therefore, more biocompatible methods were needed for the biomedical application of peptide-based hydrogels. This paper summarizes our recent work on the development of biocompatible and mild preparation methods for the peptide-based hydrogels, including enzymatic triggeration, disulfide bond cleavage, redox control and specific protein-peptide interaction inducement. These strategies showed benefits for biomedical applications of short peptide-based hydrogels, including drug delivery, analyte detection, cancer inhibition and regenerative medicine. Recently, pioneering works demonstrated that self-assembled peptides could be used as self-adjuvated vaccines through covalent conjugation of peptide or protein antigens. We found several peptide-based hydrogels that could elicit strong immune responses by simply mixing them with antigens, which showed distinct advantages over other commercially available immune adjuvants. We summarize in this review a simple strategy to deliver subunit vaccines by physically mixing antigens including DNA, protein, and attenuated cells with nanofibers of self-assembling peptides. Vaccines based on self-assembling peptides can raise stronger antibody productions, which is useful for protective vaccine development and antibody production. Besides, several vaccines capable of eliciting strong CD8+ T cell response are also introduced, and they are promising for the development of vaccines to treat important diseases such as cancers and HIV. Challenges remained are also mentioned in the last section of this review. Overall, self-assembling peptides are very useful for antibody production and the development of novel vaccines to treat important diseases.
Efficient Synthesis and Application of Protein-Poly(α-amino acid) Conjugates
Zhang Chong, Lu Hua
2018, (1): 21-31. doi: 10.11777/j.issn1000-3304.2018.17204
[Abstract](1688) [FullText HTML] (608) [PDF 13109KB](116)
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Protein-polymer conjugates are important therapeutics for various diseases. There are currently two major challenges in this field: one is the search of new biodegradable polymers beyond traditional PEGylation, and the other is to develop highly efficient and site-specific conjugation strategy. Poly(α-amino acid)s (PαAAs) are biodegradable and biocompatible polymers with tunable properties and numerous functions, making them promising candidates for protein modification. In this review, we summarize our recent progresses in protein-PαAAs conjugates. Specifically, we discuss our developments in: (1) Recent developments in the controlled ring-opening polymerization (ROP) of α-amino acid N-carboxyanhydrides (NCAs), including amine-based initiators, organometallic initiators, organosilicon amines initiators and sulfide-based initiators. For instance, trimethylsilyl phenylsulfide (PhSTMS) is a novel initiator for controlled ROP of NCAs. It exhibits higher nucleophilicity than conventional amine-based initiator, and thus affords considerably higher chain initiation rate to ensure a more controlled polymerization. Moreover, this initiator is well-tolerated to various functional groups. (2) In situ functionalization of PαAAs for site-specific protein conjugation, and construction of various topological structures. Using PhSTMS initiator, it in situ generates a reactive phenyl thioester group at one end of the PαAAs, which can be used for protein N-terminus conjugation via native chemical ligation (NCL); moreover, ROP of glycine NCA yields oligoglycine at the other end of PαAAs, which can be used for C-terminus protein conjugation via sortase-A mediated ligation (SML). More interestingly, combinatory use of the two methods can construct various topological protein-PαAA conjugates including the head-to-tail circular conjugates. (3) Development of functional PαAAs for potential protein conjugation. Various functional PαAAs have been developed as delivery materials or hydrogels. To further expand the arsenal of PαAAs for potential modulation of protein functions, PαAAs that mimic protein post-translational modifications (PTM) are synthesized; On the other hand, a series of multiple stimuli-responsive PαAAs are also produced. These PαAAs show interesting enzyme, light, and/or thermal responsiveness, which could be potentially harnessed for modulation of protein functions in the future.
Reviews
Studies on Stimulus Responsive Peptides and Their Applications in Tumor Diagnosis and Treatment
Qiu Wen-xiu, Cheng Han, Zhang Xian-zheng, Zhuo Ren-xi
2018, (1): 32-44. doi: 10.11777/j.issn1000-3304.2018.17256
[Abstract](1753) [FullText HTML] (709) [PDF 27549KB](158)
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Tumor is a most deadly killer of humans. The low therapeutic efficiency and significant side effects caused by antitumor drugs are the main problems for tumor treatment currently. The use of tumor targeting drug carrier can greatly improve the therapeutic effect and reduce the side effects of antitumor drugs. However, the complex microenvironment of tumor (such as tumor progression, the expression level of related enzymes, and precise location of tumor cells) and individual difference among cancer patients (like drug intake efficiency and drug tolerance) often lead to failure of standardized treatment modality. Therefore, to get a good knowledge of the multifarious microenvironment of tumor is important for realizing precise and personalized treatment. In order to meet these requirements, it is urgent to develop multifunctional drug carriers for tumor targeting, diagnosis, imaging, treatment and prognosis. Many kinds of strategies have been performed to meet the multifunctionality requirement of the drug carriers, such as nanotechnology, stimuli-responsive technology and so on. At the same time, many kinds of materials were developed, like organic polymer, inorganic luminescent platform, functional peptide. Among them, peptide has drawn much attention. As we know, peptide has been widely used in the construction of stimulus responsive drug delivery system because of its unique properties such as good biocompatibility, simple synthesis, versatility, high responsiveness in the organism and so on. Ideally, through the enhanced permeability and retention (EPR) effect or the active tumor targeting process, the drug delivery system with functional peptide could reach the tumor, and then the loaded drugs and varies of diagnosis signal were released under special stimulus of tumor microenvironment or exogenous stimulus. This specific stimulating response of the peptide based carrier can maximize the anticancer effect, reduce the side effects of anticancer drug and improve the accuracy of tumor diagnosis. This work briefly reviews the research progress in applications of different types of stimulus responsive peptides in tumor diagnosis and the treatment.
Glycopolypeptides: Synthesis, Self-assembly and Biomedical Applications
Xiao Chun-sheng, Ding Jian-xun, Chao-liang He, Chen Xue-si
2018, (1): 45-55. doi: 10.11777/j.issn1000-3304.2018.17282
[Abstract](1681) [FullText HTML] (632) [PDF 7906KB](126)
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Glycopolypeptides are a kind of biodegradable polymers consisting of polypeptides (polyamino acid) and carbohydrates (such as monosaccharide, oligosaccharides and polysaccharides). Owing to their chemical similarity to glycoproteins, glycopolypeptides can, to some extent, mimic the structure and function of natural glycoproteins, and have attracted broad attention recently. Two general strategies have been developed for the synthesis of glycopolypeptides, i.e. direct polymerization of glycosylated monomers and post-polymerization glycosylation of reactive polypeptides. Although the synthesis of glycopolypeptides can be traced back to sixty years ago, the synthesis of glycopolypeptides with Control architectures and high molecular weights can be achieved when high purified sugar-substituted amino acid N-carboxyanhydride (NCA) monomers for Control ring-opening polymerization and "clickable" polypeptides for "click" glycosylation have been extensively developed. Based on these advances on Control synthesis of glycopolypeptides, many efforts are devoted to studying the self-assembly of amphiphilic glycopolypeptide (co)polymers into various nano-structures, such as micelles, vesicles and nanorods. More interestingly, hierarchical self-assembly of an alternating amphiphilic glycopolypeptide to mimic the complex structure of natural glycoconjugates also has been achieved. In addition, as a kind of structural mimics of natural glycoproteins, the synthetic glycopolypeptides are capable of binding selectively to various carbohydrate-binding proteins, such as lectins. And the lectin-binding ability is confirmed to be dependent on the type, composition, density and distribution pattern of the sugar residues on the polypeptide backbone. Also, due to the presence of carbohydrate-binding proteins on cell surfaces, especially on the surface of cancer cells, glycopolypeptides have been widely investigated as biocompatible nanocarrieres for targeted drug/gene delivery. Most recently, glycopolypeptides-based hydrogels are receiving increasing attention for tissue engineering applications because of their ability to enhance cell adhesion and proliferation in 3D cell culture. In this article, we summarize recent advances in the synthesis and self-assembly of glycopolypeptides, and their applications in biomedical fields, such as biomolecular recognitions, targeted gene/drug delivery and scaffolds for tissue engineering, are also emphatically reviewed and discussed.
Papers
Synthesis and Thermoresponsive Properties of Polypeptides Bearing Phosphonium Pendants
Xiao Jiang, Li Min-jie, Tang Hao-yu
2018, (1): 56-62. doi: 10.11777/j.issn1000-3304.2018.17154
[Abstract](1384) [FullText HTML] (534) [PDF 1368KB](43)
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A series of polypeptides bearing phosphonium pendants and chloride counter anions (P1-Cl -P5-Cl) were synthesized by nucleophilic substitution between poly(γ-3-chloropropyl-L-glutamate) (PCPLG) and tributyl phosphine and/or triphenyl phosphine. Their molecular structures were verified by 1H nuclear magnetic resonance (1H-NMR)and Fourier transform infrared (FTIR). From 1H-NMR spectra, the molar content and grafting efficiency of tributyl phosphonium and/or triphenyl phosphonium moieties were calculated by integration of the characteristic proton peaks. All resulting polypeptides showed high grafting efficiency (≥ 87%). Polypeptides bearing phosphonium pendants and iodide (P1-I -P5-I) or tetrafluoroborate counter anions (P1-BF4 -P5-BF4) were synthesized by ion exchange. All polypeptides with chloride counter-anions were readily soluble in water. Nevertheless, P1-X (X = I, BF4) with exclusive tributyl phosphonium and P5-X (X = I, BF4) with exclusive triphenyl phosphonium showed poor solubility in water. It is interesting to observe that P2-I and P2-BF4 samples with appropriate molar content of tributyl phosphonium moieties (x = 0.89) showed reversible thermo-responsiveness of UCST (upper critical solution temperature). This phenomenon suggested that co-grafting or copolymerization of the two non-thermoresponsive ionic liquid moieties led to UCST type thermoresponsivenes. To the best of our knowledge, this is the first example of thermoresponsive polypeptides bearing phosphonium pendants. Variable temperature UV-Vis spectroscopy was used to study the UCST type solution phase transition behaviors of P2-I and P2-BF4. In a cooling/heating cycle, UV-Vis spectra revealed good reversibility of the UCST type phase transitions. Yet, a noticeable hysteresis was also observed. The UCST type phase transition temperature (Tpt) was also determined by UV-Vis spectroscopy at different temperatures. In DI water, the values of Tpt of P2-I and P2-BF4 were in the temperature range of 11.5 -60.2 ℃ and 45.5 -71.0 ℃, respectively, and highly dependent on counter anions, polymer concentration, nature of salts and salt concentration. Under the same experimental condition, P2-BF4 with more hydrophobic tetrafluoroborate counter anions showed higher Tpt than P2-I with iodide counter anions. Furthermore, Tpt increased with increased polymer concentration, sodium iodide or sodium tetrafluoroborate concentration. Yet, it decreased with increased sodium chloride concentration.
Synthesis of Hyperbranched Polylysine Based on Acid-base Dynamic Chemistry
Li Pan, Dong Chang-ming
2018, (1): 63-71. doi: 10.11777/j.issn1000-3304.2018.17160
[Abstract](1627) [FullText HTML] (581) [PDF 2446KB](70)
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Novel Nε-(tetrafluoroboran ammonium)-L-lysine-N-carboxyanhydride (NH3BF4-Lys NCA) was synthesized for the first time and fully characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy(1H-NMR, 13C-NMR, 19F-NMR) and time of flight mass spectroscopy (TOF-MS). When the polymerization was conducted at 20 ℃, the deactivated NH3BF4-Lys NCA does not change within 110 h, implying no polymerization occurred. However, the ionic monomer at 25 ℃ dynamically dissociates and is transformed into an activated AB* inimer type of NCA containing a primary ε-amine (i.e., inimer-NCA), which then triggers ring-opening polymerization (ROP) to produce hyperbranched polylysines salts in one-pot. The ROP of NH3BF4-Lys NCA at 25 ℃ to 55 ℃ in DMF solution conforms to first-order kinetics and the observed kinetic rate constant increases from 0.01 h-1 to 0.11 h-1, due to the enhanced dissociation kinetics of tetrafluoroboran ammonium. The resulting hyperbranched polylsines salts mainly exhibits a β-turn secondary conformation (about 70%) in solid state, as characterized by FTIR. With the polymerization temperature increased from 25 ℃ to 55 ℃, the degree of branching of the hyperbranched polylysines apparently decreases from 0.53 to 0.34, while the molar percentage of cyclic dimer units increases conversely from 6.4% to 11.5%. During the polymerization process, monomers, dimers and the resulting oligomers concomitantly dissociate to generate primary ε-amine, leading to an increasing initiator concentration coupled with a decreasing monomer concentration. By consequence, the molecular weight of the hyperbranched polymers cannot be adjusted by changing the polymerization temperature and the monomer concentration. However, the degree of branching and the molar percentage of cyclic dimer units within the hyperbranched polymers can be tuned to some extent by adjusting the polymerization temperature. Finally, both Fourier transform ion cyclotron resonance mass spectroscopy (FTICR-MS) and heteronuclear single quantum coherence spectroscopy (1H-13C HSQC) confirms that a cyclic dimer is mainly formed from the two NH3BF4-Lys NCA monomers at initial stage, which further initiates ROP to produce the hyperbranched polymers according to the well-known normal amine mechanism. Meanwhile, a little amount of NH3BF4-Lys NCA directly polymerizes itself to generate the hyperbranched polymers without forming a cyclic dimer center.
Water Tolerated Polymerization of N-Substituted Glycine N-Thiocarboxyanhydride Initiated by Primary Amines
Zheng Bo-tuo, Tao Xin-feng, Ling Jun
2018, (1): 72-79. doi: 10.11777/j.issn1000-3304.2018.17172
[Abstract](1448) [FullText HTML] (569) [PDF 1180KB](49)
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N-Substituted glycine N-carboxyanhydride (NNCA) polymerization cannot tolerate H2O, because the presence of H2O leads to oligopolymerization or deterioration of NCA. In contrast, its analogue N-substituted glycine N-thiocarboxyanhydride (NNTA) is stable to H2O. In this work, by comparing 1H-NMR spectra signal of NNTA with that of internal standard (trioxane, TOX) before and after heating for 24 h in presence of water, it is shown the tolerance of NNTA to water amount was monomer-equivalent (14000 μg/g). The polymerization of NNTA initiated by benzylamine was carried out in presence of water. 1H-NMR, MALDI-ToF-MS and SEC were used to confirm the structure of polypeptoid products. The polymerization of N-ethyl glycine NTA (NEG-NTA) initiated by benzylamine showed good tolerance to initiator-equivalent water amount (100-650 μg/g). From this polymerization, high yield (> 70%) was obtained with controlled molecular weights (1600-7500) and low molecular weight distribution (PDI, i.e. polydispersity index:1.22-1.25). Increasing amount of water (14000 μg/g) suppressed the polymerization, resulting in low yields and low molecular weights to some extent, while PDI remained low. All polymers contained benzylamine end group according to MALDI-ToF-MS, which demonstrated that all the polymerization of NNTA followed the normal amine mechanism (NAM) regardless of different water contents. Polymerizations of sarcosine NTA (Sar-NTA) and N-butyl glycine NTA (NBG-NTA) in presence of initiator-equivalent water amount were also investigated. Polymerization of sarcosine NTA resulted in high yield (89%) with controlled molecular weight and low PDI (1.13), which showed that the polymerization of NNTA with higher activity was more tolerant to water. Furthermore, the polymerization kinetics confirmed the controllability of the resulting polymer by demonstrating that the polymerization followed pseudo-first order kinetics with regard to monomer up to high conversion (~90%). In addition, molecular weights of polypeptoids exhibited linear relationship with monomer conversion while PDIs kept low. It is of great interest that well-controlled NEG-NTA polymerization was carried out in commercial THF with water content (about 190 μg/g) without dehydration. This work demonstrated that the polymerization of NNTA was a robust approach to prepare polypeptoids since both the monomer synthesis and the polymerizations did not require an anhydrous environment, which would benefit the further application of polypeptoids in bioengineering and medical field.
Inversion of Supramolecular Chirality of Nanofibrous Structures Tuned by the Odd-Even Effects among Bis-amide and Bis-urea
Liu Jin-ying, Qin Ming-gao, Y. Auphedeous Dang-i, Liu Zhi-wei, Dou Xiao-qiu, Feng Chuan-liang
2018, (1): 80-89. doi: 10.11777/j.issn1000-3304.2018.17179
[Abstract](1491) [FullText HTML] (585) [PDF 6193KB](39)
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Helicity inversion of biomacromolecules (e.g., DNA or proteins) is a sophisticated ubiquitous phenomenon in many physiological processes and associated with specific bio-functions. Therefore, designing of smart systems, with tunable helical chirality and further promoting their applications in the fields of biochemistry, biology and nano-materials, has become appealing. In this regard, four novel C2-symmetric small-molecule gelators, with L-phenylalanine and benzene ring as skeletons covalently linked by amide group (CONH) or urea group (NHCONH), are designed and synthesized. Based on the odd-even effect between the amide group (CONH) and the urea group (NHCONH), the chiral reversal of the supramolecular assembly can be regulated. The structures of the compound, a-BDFAE, u-BDFAE, a-BDFAP and u-BDFAP, were confirmed by hydrogen-1 nuclear magnetic resonance(1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR) and high resolution mass spectrum (HRMS). The hydrogels were characterized using circular dichroism spectrum (CD), and they all exhibited bisignate CD effect. However, the sign and intensity were inverted between the amide and urea molecules. The microstructure of the samples was studied using the scanning electron microscopy (SEM). They all assembled into fine nanofibers with diameter in the range of tens of micrometers. The aggregation pattern of the gelators was also investigated with a UV-Vis spectroscopy in different solvents from non-gelating (ethanol) to gelating (water). Amide molecules showed a broad band at around 241 nm in ethanol, which was red-shifted to 245 nm with the solvent changed to milli-Q water. This red-shift clearly indicates the J-type aggregation pattern of the amide hydrogelators. While the UV-Vis spectroscopy of the urea molecules showed a blue-shift, suggesting that the urea molecules formed H aggregates, a different mode of self-assembly induced by the inversion of the supramolecular chirality of amide and urea hydrogels. The interaction of supramolecular aggregates at molecular level was investigated using Fourier transform infrared spectroscopy (FTIR). The results demonstrated that the inversion of the supramolecular chirality of nanofibrous structures was tuned by the odd-even effects, providing therefore a new method for the designing of the tunable supramolecular chirality system. This kind of material has the advantages of simple synthesis, good gelation performance, good biocompatibility. Further biology study of the effects of different chiral materials on cell adhesion and proliferation, and differentiation of stem cells are under way in our laboratory.
Temperature-responsive Polymer Conjugation of Interferon-α Enhances Antitumor Efficacy
Liu Xin-yu, Hu Jin, Guo Jian-wen, Wang Gui-lin, Gao Wei-ping
2018, (1): 90-98. doi: 10.11777/j.issn1000-3304.2018.17195
[Abstract](603) [FullText HTML] (350) [PDF 14705KB](46)
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Interferon-α (IFN) has a short circulating half-life, which not only leads to limited clinical efficacy, but also causes severe side effects and poor patient compliance. Previously, we developed ELPfusion and site-specific in situ growth (SIG) methods to prolong the half-life of IFN, while the adopted intravenous administration still could not well concentrate IFN inside tumour tissues. In order to enhance the tumour accumulation and antitumour efficacy of IFN, in this study, we report intratumoural administration of temperature responsive interferon-poly(di(ethylene glycol) methyl ether methacrylate) conjugates (IFN-PDEGMA). First, we employed SIG method to synthesize a series of temperature responsive IFN-PDEGMAs with different molecular weights (10 kDa, 30 kDa, 60 kDa and 100 kDa). The preparation process was monitored by SDS-PAGE, and the molecular weights, hydrodynamic radius and secondary structures of conjugates were characterized by GPC, DLS and CD (circular dichroism), respectively. The phase transition temperatures were determined to be around 22℃. Thus, IFN-PDEGMA were soluble below 22℃; and they became insoluble above 22℃. Since the body temperature of mice is above 22℃, IFN-PDEGMA injected into the tumour tissue of mice aggregated locally and became a drug depot in the tumour. In vitro characterization demonstrated that the structure and anti-proliferative activity of IFN were well remained for IFN-PDEGMA. In vivo experiments showed that the survival time of A375 melanoma-bearing mice were well extended by IFN-PDEGMA treatment compared with IFN-α. To be specific, the survival times of mice treated by IFN-PDEGMA of 10 kDa, 30 kDa, 60 kDa and 100 kDa were 36.5, 31, 29.5 and 28 days, respectively. IFN-PDEGMA of 10 kDa and 30 kDa both exhibited better anti-melanoma efficacy than commercial long-acting interferon, PEGASYS. Meanwhile, the biological safety experiments also showed that IFN-PDEGMA treatment did not have obvious side effects on normal tissues. In summary, we, for the first time, reported intratumoural administration of temperature responsive IFN-PDEGMA and studied the rule about how the molecular weight impacts on their properties in vitro and in vivo. This study not merely displayed an instance of temperature responsive protein-polymer conjugates and their anti-tumour efficacy, but also provided inspiration to further build a series of smart protein-polymer conjugates and seek for their potential applications in the diagnosis and treatment of major diseases such as cancer, virosis, diabetes and cardiovascular disease.
Preparation of Poly(L-glutamic acid)-based Hydrogels via Diels-Alder Reaction and Study on Their Biomolecule-responsive Properties
Zhang Zhen, He Chao-liang, Xu Qing-hua, Zhuang Xiu-li, Chen Xue-si
2018, (1): 99-108. doi: 10.11777/j.issn1000-3304.2018.17221
[Abstract](729) [FullText HTML] (381) [PDF 15080KB](56)
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A novel type of biomolecule-responsive polypeptide hydrogels were fabricated by inverse electron demand Diels-Alder reaction between disulfide-linked, norbornene-conjugated poly(L-glutamic acid) (PLG-SS-Norb) and tetrazine-teminated 4-armed poly(ethylene glycol) (PEG-T). Mono-norbornene group modified cystamine (Norb-SS-NH2) was synthesized and then introduced into the side chains of PLG through EDC/NHS chemistry. The obtained polymer was mixed with PEG-T to form the hydrogels in phosphate buffer saline (PBS) at various polymer concentrations and PLG-SS-Norb/PEG-T mass ratio. The gelation was accomplished in several minutes via inverse electron demand Diels-Alder reaction between the norbornene and tetrazine groupswith nitrogen as the byproduct. The mechanical properties were investigated by dynamic mechanical analysis, which indicated that the storage moduli of the hydrogels were influenced by polymer concentration and the molar ratio of two functional groups. Due to the peptide linkage in poly(L-glutamic acid) (PLG) backbone and disulfide bonds in the crosslinking points, the hydrogels were sensitive to proteolitic enzymes and thiol-containing reductive biomolecules. The degradation of the hydrogel was markedly accelerated in the presence of glutathione (GSH) or elastase in vitro. Particularly, dynamic mechanical analysis revealed a remarkabe decrease in the storage moduli from 3.3 kPa to 0.51 kPa within 12 h in the presence of 0.8 mmol/L GSH, and the influence of GSH treatment on the hydrogel was also clearly demonstrated by changing pore structure in scanning electron microscopy (SEM) images. After subcutaneous injection into rats, PLG/PEG hydrogel linked with disulfide bonds completely degraded in 6 days and displayed obviously enhanced degradation rate compared to the counterpart without disulfide bonds. Moreover, MTT assay showed that nearly 90% of L929 cells remained viable after incubation with PLG-SS-Norb or PEG-T at concentrations up to 1 g/L. The live/dead cell staining assay and the histology analysis showed that the polypeptide hydrogel exhibited good cytocompatibility in vitro and histocompatibility in vivo.
Effect of Intermolecular Interactions on Self-assembled Structures of Polypeptide-based Copolymer/Polystyrene Derivatives Blends
Zhang Shuo, Cai Chun-hua, Huang Qi-jing, Lin Jia-ping, Xu Zhan-wen
2018, (1): 109-118. doi: 10.11777/j.issn1000-3304.2018.17223
[Abstract](808) [FullText HTML] (389) [PDF 12270KB](48)
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Herein, poly(γ-benzyl-L-glutamate)-b-poly(ethylene glycol) (PBLG-b-PEG) polypeptide-based rod-coil block copolymer, polystyrene homopolymer (PS), and PS derivatives, such as poly(4-acetoxystyrene) (PAS) homopolymer, poly(vinylphenol) (PVPh) homopolymer, and poly(styrene-co-4-acetoxystyrene) (P(S-co-AS)) copolymer with various AS molar contents, were synthesized. The molecular structures (molecular weight, polydispersity index and composition) of the polymers were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (1H-NMR) and gel permeation chromatography (GPC). Self-assembly behaviors of the polymer blends composed of PBLG-b-PEG copolymer and PS derivatives (including PS homopolymer) were explored. The self-assembled aggregates were prepared by a dialysis method with water used as selective solvent. The morphologies and structures of the formed aggregates were investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The influence of intermolecular interaction between polymers (e.g., π-π interaction between PBLG and PS, PAS and PVPh, dipole-dipole interaction between PBLG and PAS, and hydrogen-bonding interaction between PBLG and PVPh) on self-assembly behaviors of the polymer blends was investigated. With the strength of intermolecular interaction increasing in the order of PBLG/PS < PBLG/PAS < PBLG/PVPh, a morphological transition was observed. With relatively weak intermolecular interaction, strip-pattern-spheres were formed in the PBLG-b-PEG/PS blends. For PBLG-b-PEG/PAS blends, as the dipole-dipole interaction was stronger than π-π interaction, the strips disappeared and cavity was observed. As the intermolecular interaction was further enhanced by hydrogen bonding, vesicles were self-assembled in PBLG-b-PEG/PVPh blends. Additionally, the surface morphology of the spherical aggregates was tuned by AS molar content and temperature for PBLG-b-PEG/P(S-co-AS) blends. With increasing AS molar content, the dipole-dipole interaction between PBLG and P(S-co-AS) increased, leading to less regular strip patterns on aggregates surfaces compared with PBLG-b-PEG/PS polymer blends. As temperature increases, the strip patterns became more regular due to the weaker interaction between PBLG and PSAS segments.
Antibacterial Hydrogels Incoporated with Poly(glutamic acid)-based Vesicles
Song Tao, Xi Yue-jing, Du Jian-zhong
2018, (1): 119-128. doi: 10.11777/j.issn1000-3304.2018.17229
[Abstract](905) [FullText HTML] (470) [PDF 36716KB](122)
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We designed a hydrogel with durable and excellent antibacterial activity. Amphiphilic block copolymer, polycaprolactone-block-poly(glutamic acid) (PCL-b-PGA), was first synthesized by ring-opening polymerization with amine-terminated polycaprolactone (PCL-NH2) as the macro-initiator and Bz-Glu-NCA as the monomer. This copolymer self-assembled into vesicles in solvent mixture of DMF/water with a critical vesiculation concentration of 5.27 μg mL-1. Antibacterial Ag-decorated vesicles were then prepared by in situ deposition of silver nanoparticles in PGA coronas of the vesicles as a result of the electrostatic interaction between carboxyl groups and Ag+. 1H-NMR analysis revealed the composition of PCL47-b-PGA46 block copolymer. Dynamic light scattering (DLS) study revealed an intensity-averaged diameter of 215 nm for the vesicles with a polydispersity of 0.029. Transmission electron microscopy (TEM) confirmed a hollow structure of the vesicles with a number-averaged diameter of 270 nm, and the presence of sliver nanoparticles on the vesicles. Atomic force microscopy (AFM) revealed the collapsed surface morphology of vesicles with a width to height ratio of 18, confirming further the hollow structure of the vesicles. Meanwhile, Ag-decorated vesicles were incoporated into Pluronic F127 hydrogels to afford antibacterial hydrogels, showing good degradability at different pH. MIC90(minimum concentration of inhibiting 90% of bacterium) of the antibacterial vesicles was 10 μg mL-1 against Gram-negative bacterium E. coli, and it was 20 μg mL-1 against Gram-positive bacterium S. aureus, and measured by spread plate method, which afford the hydrogels excellent antibacterial property. Oxford cup tests confirmed that MIC50 of the antibacterial hydrogel against both E. coli and S. aureus is 7.5 μg mL-1 and MBC (minimum bactericidal concentration) against both of them is 30 μg mL-1. The in vitro degradation tests confirmed that the vesicle was degraded in the presence of lipase. Overall, we provide a new method for preparation of antibacterial hydrogels, which may have promising biomedical applications requiring a long-acting antibacterial therapy such as inflammation triggered by bacteria infection, wound healing after surgery and sterilization for the implant devices, etc.
  • Editor: Xi Zhang

    Establishment Time: 1957

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    Sponsors by: ICCAS
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