Revolutionizing wild silk fibers: Ultrasound enhances structure, properties, and regenerability of protein biomaterials in ionic liquids.

Ultrasound-assisted regulation of biomaterial properties has attracted increasing attention due to the unique reaction conditions induced by ultrasound cavitation. In this study, we explored the fabrication of wild tussah silk nanofiber membranes via ultrasound spray spinning from an ionic liquid system, characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), atomic force microscopy (AFM), water contact angle, cytocompatibility tests, and enzymatic degradation studies. We investigated the effects of ultrasound propagation in an ionic liquid on the morphology, structure, thermal and mechanical properties, surface hydrophilicity, biocompatibility, and biodegradability of the fabricated fibers. The results showed that as ultrasound treatment time increased from 0 to 60 min, the regenerated silk fiber diameter decreased by 0.97 μm and surface area increased by 30.44 μm, enhancing the fiber surface smoothness and uniformity. Ultrasound also promoted the rearrangement of protein molecular chains and transformation of disordered protein structures into β-sheets, increasing the β-sheet content to 54.32 %, which significantly improved the materials' thermal stability (with decomposition temperatures rising to 256.38 °C) and mechanical properties (elastic modulus reaching 0.75 GPa). In addition, hydrophilicity, cytocompatibility, and biodegradability of the fiber membranes all improved with longer ultrasound exposure, highlighting the potential of ultrasound technology in advancing the properties of natural biopolymers for applications in sustainable materials science and tissue regeneration.