Preparation of Silk Fibroin Nanofibers/Nanocrystals through TEMPO/Laccase/O ₂ Oxidation

Nanomaterial-based hydrogels derived from natural silk have garnered significant attention in advanced applications. However, preparation of silk fibroin nanofibers by directly disintegrating natural silk fibers remains challenging. We initiated the process by employing various pretreatment methods to loosen the intricate structure of the natural silk fibers. Subsequently, carboxyl groups were introduced to the silk fibroin surface using a sequential TEMPO/Laccase/O₂ (TLO) oxidation approach, whereby the fabrication of silk nanofibers (TLO-SNFs) or nanocrystals (TLO-SNCs) was achieved with a high carboxyl content (ranging from 0.795 to 0.935 mmol/g) and nanofiber lengths of up to 1843 ± 659 nm. Furthermore, TLO-SNFs were further incorporated with poly(<i>N</i>-isopropylacrylamide) (PNIPAm) through acetic acid coagulation, whereby a reinforced TLO-SNF@PNIPAm hydrogel was constructed with an interpenetrating network. It exhibited excellent mechanical performance and demonstrated shape-retaining shrinkage-expansion capabilities, significantly extending the release time of curcumin to 2 weeks. This makes TLO-SNF@PNIPAm an ideal carrier for the long-term in vitro release of curcumin, offering potential applications in responsive transdermal patches.