A silk fibroin hydrogel with reversible sol-gel transition

Abstract

In this report, a novel silk fibroin hydrogel with a reversible sol-gel transition capacity is presented, in which the base material of this reversible hydrogel is hydrophilic silk fibroin (HSF) obtained by immersing a dried regenerated Bombyx mori silk fibroin (SF) condensate in deionized water (DI water) and collecting its lixivium. The resulting HSF sol can exhibit an enhanced sol-gel transition within several hours at suitable temperatures (25-50 °C) without any exterior additive, even at extremely low concentrations (<0.2%, w/v). The HSF gel can perform thixotropic, reversible gel-sol transitions triggered by a facile cycled shear-thinning and resting procedure. Reversible sol-gel transition kinetics analyses and dynamic measurements of the micro-structure transformation during the transition demonstrate that both the β-sheet self-assembling process and metastable hydrogen bonding (H-bond) interactions among these large scale β-sheet aggregates play essential roles in the significant enhancement of the reversible HSF sol-gel transition. Due to the reversible, thixotropic sol-gel transitions and suitable viscoelasticity of its shear-thinning system for matching random sizes/shapes, the HSF system is possibly an alternative injectable hydrogel for applications in 3-dimensional (3D) cell culture and tissue repair in situ.