Silk screws prepared by bidirectional dialysis for bone fracture fixation

Resorbable devices for fracture fixation have gained extensive interest owing to their ability to avoid secondary surgery. Silk, as a biomaterial, is considered a promising candidate for fixation systems due to its biocompatibility, remarkable mechanical properties, and controllable degradation. However, the current methods for preparing silk fixation devices are complex and time-consuming, involving multiple processes, including dissolution, dialysis, lyophilization, etc. Here, we report a novel approach for fabricating silk fixation devices directly from a silk-LiBr solution through bidirectional dialysis. As the concentration of lithium bromide decreases and the ethanol concentration increases, the silk-LiBr solution undergoes a structural transition to β-sheet, resulting in hydrogel formation. The hydrogel is further processed into a robust silk fixation system through drying and machining. The obtained silk screw demonstrated a maximum compression modulus of 1.47 GPa. In vivo experiments demonstrated that the silk fixation system exhibits good biocompatibility and maintains fixation stability for up to 4 months. Notably, the silk-based screw retained 94.8 % of its weight after four months in rats. The significance of this study lies in the development of a fabrication technique that enables the direct processing of silk-LiBr solution into diverse material formats with tunable structures and properties.