Antioxidant High-Fluorescent Silkworm Silk Development Based on Quercetin-Induced Luminescence

The fluorescent silk produced by feeding silkworms with traditional fluorescent dyes is limited in functionality and suffers from fluorescence quenching, rendering it unsuitable for long-term stable performance as a medical implant material in the human body. This work introduces an innovative strategy to develop a novel multifunctional fluorescent silk composite by incorporating quercetin (QR), a naturally occurring molecule with aggregation-induced emission (AIE) characteristics, into the diet of silkworms. Silk derived from QR-fed silkworms presents significant enhancements in fluorescence, antioxidant, and mechanical properties, with the QR-2.5% group presenting the best overall performance. The resulting silk exhibits superstrong blue fluorescence when exposed to 405 nm laser light, with a breaking strength of 4.26 ± 0.42 cN/D and a breaking energy of 5.96 ± 1.32 cN/cm, improvements of 15.76% and 18.25%, respectively, in comparison with regular silk. Fourier transform infrared spectroscopy (FTIR) analysis indicates that QR induces a structural transformation of fibroin protein from α-helix and random coil to β-sheet configuration, thereby increasing silk crystallinity. Additionally, compared with regular silk, the antioxidant properties of both sericin and silk fibroin increased by 88.66% and 17.25%, respectively. At the same time, this multifunctional silk has excellent biocompatibility and strong cell adhesion. The high-strength, uniformly luminescent silk developed in this study has outstanding antioxidant and mechanical properties. It effectively avoids the fluorescence quenching issue common in traditional fluorescent silk materials and introduces new functionalities. This advancement is significant for increasing the utility of functionally modified silk.