Biosynthesis of Gold Core Silver Shell Bimetallic Nanoparticles by using Solanum lasiocarpum Dunal Leaf Extract

In contrast to conventional techniques that use hazardous chemicals and high energy, plant-mediated nanoparticle synthesis offers an economical and eco-friendly alternative. Solanum lasiocarpum Dunal leaf extract contains bioactive compounds capable of reducing and stabilizing metal ions for nanoparticle formation. Gold core–silver shell bimetallic nanoparticles (Au@Ag NPs) were synthesized using three volumes of extract: Sample 1 (25 mL), Sample 2 (50 mL), and Sample 3 (75 mL). Characterization was performed by UV–Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDX). Antimicrobial activity was assessed by agar well diffusion, antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, and cytotoxicity by brine shrimp lethality. Antimicrobial assays showed inhibition zones of 10.8–13.9 mm ( Staphylococcus aureus ), 9.5–10.2 mm ( Bacillus cereus ), 10.4–11.1 mm ( Escherichia coli ), 11.0–13.4 mm ( Pseudomonas aeruginosa ), and 9.6–9.9 mm ( Candida albicans ). Antioxidant activity ranged from 10.91–64.36% scavenging, with half maximal inhibitory concentration (IC₅₀) values of 89.99% (Sample 1), 76.67% (Sample 2), and 57.64% (Sample 3). Cytotoxicity tests revealed dose-dependent mortality with median lethal concentration (LC₅₀) values of 73.38% (Sample 1), 87.22% (Sample 2), and 86.53% (Sample 3). Biosynthesized Au@Ag NPs demonstrated effective antimicrobial, antioxidant, and cytotoxic properties, with Sample 3 showing the strongest activity. These findings highlight Au@Ag NPs from S. lasiocarpum as a sustainable alternative to chemically synthesised nanoparticles.