Green synthesis of noble metal nanoparticles using cysteine-modified silk fibroin: catalysis and antibacterial activity

Abstract

Noble metal nanoparticles (NPs) have shown remarkable potential for numerous applications. In this work, a simple, one-pot, green method for the synthesis of gold, silver, palladium, and platinum NPs by using thiol-modified silk fibroin (SF-SH) has been described. The incorporation of thiol groups into silk fibroin (SF) yields small, mono-dispersed metal nanoparticles with good colloidal stability. UV-Vis, transmission electron microscopy (TEM), and X-ray powder diffraction (XRD) analyses show the formation of NPs, and thermo-gravimetric analysis (TGA) data reveal interaction of the NPs with thiol-modified SF. We also show that all the NP–SF conjugates catalyse the reduction of p-nitrophenol to p-aminophenol in the presence of NaBH₄ at room temperature. The NP–SF conjugate materials were processed into different material formats like porous scaffolds and films without compromising their individual properties. The Au–SF–SH composite scaffold was used successfully in the heterogeneous catalysis of p-nitrophenol reduction using NaBH₄ while the Ag–SF–SH conjugated film showed good antibacterial activity.