Water-stable silk fibroin nerve conduits with tunable degradation prepared by a mild freezing-induced assembly

Silk fibroin (SF) is considered as an attractive candidate biomaterial for soft tissue regeneration. However, chemical treatments are normally required to achieve water-stability of regenerated SF materials and thus hinder its widespread applications. In this study, an all-water-based strategy was developed to prepare water-insoluble SF nerve conduits by freezing-induced structural transition. A facile freezing processing named soft freezing was used to induce the structural transition of SF from amorphous to silk I structure, consequently rendering the SF conduits water-stable. XRD and FTIR results clearly showed that the freezing-stabilized SF conduit is silk I-dominant structure. The conduit showed enhanced flexibility compared with the traditional ethanol-induced SF conduits because of reduced beta-sheet content and high content of silk I structure. The reduced stiff makes SF conduit soft enough for matching peripheral nerve tissue regeneration. The fabrication process is mild, including all-aqueous, low temperature, and without the addition of any chemicals. Furthermore, the enzymatic degradation behavior of the SF conduits with silk I structure was investigated, revealing that the degradation rate could be effectively regulated by degumming-controlled molecular weight change of silks. The results offer useful options to prepare bioactive SF scaffolds for peripheral nerve regeneration. (C) 2019 Elsevier Ltd. All rights reserved.