Silk fibroin (SF) hydrogel is a promising candidate in biomaterial field; however its application is quite limited by long-gelation time. In the present study, we developed a novel strategy named soft freezing to accelerate the process and control the sol-gel transition of SF protein. SF protein was induced to self-assembly by soft freezing process for achieving the reconstructed SF solution with metastable structure. It was found that the soft freezing process triggers the structural transition from random structure to ordered structure-rich conformation. Gelation kinetics showed that the gelation time of SF protein could be regulated by changing freezing time and initial concentration. The reconstructed SF solution allowed enhanced sol-gel transition within 6 hours, even at extremely low concentration. The attractive features of the method described here include the accelerated gelation, free of chemical agents, and reducing processing complexity. The SF solution with short gelation time will be applicable as cell encapsulation and injectable applications for tissue engineering and regenerative medicine, which greatly expand the applications of SF hydrogels.

丝素蛋白（SF）水凝胶是生物材料领域的有希望的候选者。但是，它的应用受到长时间胶凝的限制。在本研究中，我们开发了一种名为“软冷冻”的新策略，以加速该过程并控制SF蛋白的溶胶-凝胶转变。通过软冰冻过程诱导SF蛋白自组装，从而获得具有亚稳结构的SF蛋白重建溶液。发现软冻结过程触发了从无规结构到有序结构丰富的构象的结构转变。凝胶动力学表明，SF蛋白的凝胶时间可以通过改变冷冻时间和初始浓度来调节。重构后的SF溶液即使在极低的浓度下也能在6小时内增强溶胶-凝胶的转变。这里描述的方法的吸引人的特征包括加速的凝胶化，无化学试剂和降低加工复杂性。胶凝时间短的SF溶液可用于组织工程和再生医学的细胞封装和注射应用，这将极大地扩展SF水凝胶的应用范围。