Sustainable Synthesis of Metal Nanoparticles and Assessment of Their Biological Effects

Abstract

The development of environmentally friendly methods for nanoparticle synthesis has gained significant attention due to growing concerns about environmental sustainability and the toxicity of conventional chemical approaches. This study presents a comprehensive investigation of green synthesis methods for silver (Ag), gold (Au), and zinc oxide (ZnO) nanoparticles using plant extracts, followed by a systematic evaluation of their biological effects. We employed Azadirachta indica (neem) leaf extract as a reducing and stabilizing agent for the biosynthesis of metal nanoparticles. The synthesized nanoparticles were characterized using UV-visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). Biological activities were assessed through antimicrobial assays, cytotoxicity studies, and antioxidant evaluation. Results demonstrated successful synthesis of spherical nanoparticles with average sizes of 15-25 nm for Ag, 20-30 nm for Au, and 25-35 nm for ZnO. The green-synthesized nanoparticles exhibited significant antimicrobial activity against both Gram-positive and Gram-negative bacteria, with minimum inhibitory concentrations (MIC) ranging from 12.5 to 50 μg/mL. Cytotoxicity studies revealed dose-dependent effects, with IC50 values of 45.2, 67.8, and 38.9 μg/mL for Ag, Au, and ZnO nanoparticles, respectively. This study demonstrates the potential of plant-mediated synthesis as a sustainable alternative for nanoparticle production with promising biomedical applications.