Highly stable colloidal gold nanoparticles using biopolymer silk sericin: Characterization and antibacterial activity

Abstract

In the current research, highly stable gold nanoparticles (AuNPs) were synthesized using Bombyx mori silk sericin (SS) a facile, cost effective and environmental benign approach has been reported. The SS is a bio-material, playing the dual role as reducing and stabilizing agent of the AuNPs. The formation and the stability of the synthesized SS-AuNPs were studied before and after 9 months using UV–Visible (UV–Vis) spectroscopy. The study confirms the formation of the stable AuNPs by showing optical absorption λ max around 519–528 nm. Fluorescence emission (FL) study revealed the phenolic groups in the tyrosine residue was the most active functional group able to convert the Au 3+ ion to Au 0 atoms. Cubic structure and crystalline aspects of AuNPs were probed using X-ray diffraction (XRD) measurements. Size, shape morphology of the AuNPs before and after 9 months were characterized using high resolution transmission electron microscopy (HR-TEM). It was found that most of the particles were spherical in shape with average size 6.02 ± 0.77 nm. The size distribution and zeta potential was carried out using dynamic light scattering (DLS) experiment. Further, potential antibacterial activity of the SS-AuNPs was evaluated against selected plant pathogen Ralstonia solanacearum and the results showed concentration dependent zones of inhibition.