Sericin–copper-functionalized silk fabrics for enhanced ultraviolet protection and antibacterial properties using response surface methodology

This study investigated the enhancement of the ultraviolet (UV) protection and antibacterial properties of functionalized silk fabrics using a simple, inexpensive and environmental friendly approach. We demonstrated the in situ synthesis of copper nanoparticles (CuNPs) in a silk sericin (SS) matrix, using ascorbic acid as both a reducing agent and antioxidant. Development and optimization was achieved using a central composite design (CCD) in conjunction with the response surface methodology (RSM). The goal was to identify the concentrations of CuSO₄ and SS that produced the optimal balance between UV protection and antibacterial activity, when tested against Escherichia coli and Staphylococcus aureus. The SS-CuNP bio-nanocomposites were characterized using scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. Statistical analyses indicated that an empirical second-order polynomial could accurately describe the UV protective factor, % reduction of S. aureus and % reduction of E. coli. The three-dimensional response surface graphs showed that the optimal concentrations of CuSO₄ and SS were 2380 and 9500 ppm, respectively. To confirm that the levels identified using RSM were optimal in practice, performance evaluations were conducted. These investigated the durability and stability of UV protection and antibacterial activity after repeated washing cycles. The results suggest that these bio-nanocomposites have great potential for the multifunctionalization of silk fibers.