α-螺旋聚氨基酸交联的水凝胶的制备和材料特性

Preparation and Material Properties of α-Helical Polypeptides Crosslinked Hydrogel

聚氨基酸作为一种主链结构和天然蛋白质相同的合成高分子,能够形成多种二级结构,为调节材料的宏观性能提供了新的维度.为系统研究二级结构对聚氨基酸材料的影响,本工作分别设计了α-螺旋和无规线团结构的聚氨基酸交联剂,并构建了两类以不同二级结构聚氨基酸交联的水凝胶.通过比较两类水凝胶的流变和拉伸性能,研究了聚氨基酸的α-螺旋结构对水凝胶力学性质的影响.结果表明,与无规线团聚氨基酸交联的水凝胶相比,螺旋聚氨基酸交联的水凝胶表现出更大的刚性、更高的韧性和快速恢复的特征,展现出α-螺旋作为分子弹簧的特性与作为高力学性能水凝胶增强元件的潜力.

Polypeptides are synthetic polymers with a similar main chain structure to proteins,which can form various secondary structures,providing a new dimension for regulating the macroscopic properties of materials.To investigate the effect of secondary structures on the properties of polypeptide materials,we designed polypeptide crosslinking agents withα-helical and random coil structures.We synthesized glutamic acid derivatives with triethylene glycol monomethyl ether as the side chain,and subsequently prepared them as N-carboxy anhydride(NCA)monomers.We then used a tetra-armed initiator to initiate single chiral NCAs and a 1∶1 mixture of enantiomeric NCAs to respectively prepareα-helical and random coil structured polypeptides.Acryloyl chloride was used to modify the end groups of the polypeptides so that they could be introduced as crosslinking agents into the polyacrylamide network of N,N-dimethylacrylamide(DMAM),resulting in the preparation of hydrogels crosslinked with polypeptides of different molecular weights and secondary structures.By comparing the swelling ratio,rheological and tensile properties of the two hydrogels,we studied the effect ofα-helical structure of polypeptides on the mechanical properties of hydrogels.The results of swelling tests in aqueous solutions showed that,hydrogels crosslinked with random coil polypeptides exhibited better swelling performance compared to those crosslinked withα-helical structure polypeptides.The smaller mesh size ofα-helical peptide networks resulted in fewer water molecules entering during swelling.Rheological characterization revealed that helical peptide hydrogels had lower critical strain and higher storage modulus,and exhibited faster recovery ability due to the high cooperativity of hydrogen bonds.Tensile experiments were conducted,and stress-strain curves were obtained.α-Helical polypeptide crosslinked gels exhibited higher fracture strength but lower fracture strain compared to random coil polypeptide crosslinked gels.The helical structure required a higher force to break the amide bonds due to multiple hydrogen bonds,resulting in lower extensibility.The elastic modulus of helical gels was significantly higher,independent of the crosslinker's molecular weight.Moreover,helical gels had higher fracture energy due to hydrogen bond dissociation and energy dissipation.According to these results,the hydrogel crosslinked withα-helical polypeptides exhibited greater rigidity,higher toughness,and faster recovery compared with the hydrogel crosslinked by random coil polypeptides,demonstrating the characteristics ofα-helices as molecular springs and their potential as enhancers for high-performance hydrogels.