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Shengchen Huang1

1, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, , China

Genetically engineered protein copolymers, which can combine different unique peptide sequences derived from natural protein materials, offer great opportunities for making advanced materials with tailored mechanical properties and self-assembling propensities. Here we report for the first time biosynthesis and self-assembly of a recombinant resilin−silk (RS) copolymer consisting of repeating units of silk and resilin blocks. The copolymer in aqueous solution self-assembled into diverse types of nanostructures in processes that are temperature-dependent, and the assembled nanoparticles further form nano- to microscale fibers in a time-dependent manner at body temperature, whereas such fibers were not formed upon incubation of the copolymer at either low or high temperatures. In contrast, a resilin-like polypeptide without the silk blocks exhibited a typical thermoresponsive dual-phase transition behavior and was incapable of selfassembling into fibers. More interestingly, the microscale fibers self-assembled from a moderately concentrated RS solution (20 wt %) could interact to give a self-supporting, semitransparent hydrogel with elastic modulus at approximately 195 Pa. Furthermore, photo-cross-linking of either freshly prepared or annealed RS copolymer led to the formation of stiff hydrogels and the material mechanical property was superior upon annealing of the RS solution for a longer time up to 4 h, with elastic modulus ranging from 2.9 to 7.0 kPa. These results not only shed light on the fundamental hierarchical assembly mechanism of a new family of genetically engineered RS copolymer but also suggest future opportunities for these thermoresponsive polymers in fabrication of hydrogel materials with tunable mechanical properties for diverse applications.

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