Song Huijuan, Yang Guang, Huang Pingsheng, Kong Deling, Wang Weiwei
Tianjin Key Laboratory of Biomaterial Research, Institute of Biomedical Engineering, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin 300192, China.
J Mater Chem B. 2017 Mar 7;5(9):1724-1733. doi: 10.1039/c6tb02969h. Epub 2017 Feb 9.
Self-assembled polypeptide aggregates have shown great promise in biomedical fields including drug delivery, tissue regeneration and regenerative medicine. In this study, we report self-assembled hydrogels based on mPEG-block-poly(l-valine) (PEV) copolymers. PEV copolymers with varying poly(l-valine) chain lengths were prepared by the ring-opening polymerization of N-carboxy anhydrides of l-valine using mPEG-NH as the initiator. H NMR and GPC confirmed their well-defined chemical structures. FT-IR analysis and DSC curves indicated the combined α-helix and β-sheet secondary polypeptide conformation and the PEG crystallization microphase in bulk solid state, respectively. Moreover, the poly(l-valine) block restricted the crystallization of PEG segment. DLS, TEM and circular dichroism spectra were employed to study the self-assembly profiles of PEV copolymers in aqueous solution. The results manifested that in diluted solution, PEV copolymers showed a combination of typical β-sheet and α-helical polypeptide structures and self-assembled into nanostructures with diverse morphologies and sizes. For concentrated PEV solutions, clear hydrogel phases were observed and dynamic rheological analyses demonstrated that the hydrogel modulus was sensitive to the polypeptide length, angular frequency, shear strain and temperature. The hydrogel formation was possibly dominated by the physical aggregation of PEV nanoassemblies as well as driven by the formation of particular polypeptide secondary structures. Human fibroblast NIH/3T3 cells were encapsulated and cultured within the hydrogel scaffolds. The encapsulated cells exhibited high viability, suggesting that PEV hydrogels have excellent cytocompatibility and could be used as three-dimensional (3D) cell culture matrices. Collectively, self-assembled PEGylated poly(l-valine) conjugate hydrogels represented a new kind of biomaterial scaffold in biomedical fields including but not limited to 3D cell culture.
自组装多肽聚集体在包括药物递送、组织再生和再生医学在内的生物医学领域已展现出巨大潜力。在本研究中，我们报道了基于甲氧基聚乙二醇-聚（L-缬氨酸）（PEV）共聚物的自组装水凝胶。使用甲氧基聚乙二醇-氨基（mPEG-NH）作为引发剂，通过L-缬氨酸N-羧基酐的开环聚合制备了具有不同聚（L-缬氨酸）链长的PEV共聚物。核磁共振氢谱（¹H NMR）和凝胶渗透色谱（GPC）证实了它们明确的化学结构。傅里叶变换红外光谱（FT-IR）分析和差示扫描量热法（DSC）曲线分别表明了在本体固态中存在组合的α-螺旋和β-折叠二级多肽构象以及聚乙二醇（PEG）结晶微相。此外，聚（L-缬氨酸）嵌段限制了PEG链段的结晶。采用动态光散射（DLS）、透射电子显微镜（TEM）和圆二色光谱研究了PEV共聚物在水溶液中的自组装情况。结果表明，在稀溶液中，PEV共聚物呈现出典型的β-折叠和α-螺旋多肽结构的组合，并自组装成具有不同形态和尺寸的纳米结构。对于浓缩的PEV溶液，观察到了清晰的水凝胶相，动态流变学分析表明水凝胶模量对多肽长度、角频率、剪切应变和温度敏感。水凝胶的形成可能主要由PEV纳米聚集体的物理聚集主导，同时也受特定多肽二级结构形成的驱动。将人成纤维细胞NIH/3T3封装在水凝胶支架中进行培养。封装的细胞表现出高活力，表明PEV水凝胶具有优异的细胞相容性，可作为三维（3D）细胞培养基质。总的来说，自组装聚乙二醇化聚（L-缬氨酸）共轭水凝胶代表了生物医学领域中一种新型的生物材料支架，包括但不限于3D细胞培养。
