Green Synthesis of Silver Nanoparticles using Azadirachta indica Leaf Extract: Structural Characterisation, Antibacterial Activity, Statistical Evaluation and Cytotoxicity Assessment

Sustainable approaches for nanoparticle fabrication are gaining increasing importance due to environmental and health concerns associated with conventional chemical synthesis. In the present work, silver nanoparticles (AgNPs) were synthesized using aqueous leaf extract of Azadirachta indica as a natural reducing and stabilizing medium. Formation of nanoparticles was confirmed using FTIR, XRD, and TEM analyses. XRD results demonstrated a highly crystalline face-centred cubic (FCC) structure with an estimated crystallite size of 10–12 nm calculated using the Scherrer equation. TEM imaging revealed predominantly spherical and well-dispersed nanoparticles with a lattice fringe spacing of 0.235 nm corresponding to the (111) plane of metallic silver. FTIR spectra confirmed the participation of phytochemicals in nanoparticle reduction and surface stabilisation. The biosynthesized AgNPs showed strong antibacterial activity against Escherichia coli and Staphylococcus aureus, with inhibition zones of 18 ± 0.8 mm and 16 ± 0.6 mm, respectively. Minimum inhibitory concentrations (MICs) were determined as 25 µg/mL and 20 µg/mL. One-way ANOVA indicated statistically significant differences among treatment groups (p < 0.05). Cytotoxicity evaluation using the MTT assay demonstrated greater than 85% cell viability at concentrations ≤25 µg/mL, indicating acceptable cytocompatibility. The findings confirm that neem-mediated AgNPs offer a sustainable and biologically compatible nanomaterial suitable for antimicrobial and environmental applications.