Process Optimization for Green Synthesis of Silver Nanoparticles using <i>Acalypha godseffiana</i> Leaves Extract and its Biological Activity Against MRSA

Methicillin-resistant Staphylococcus aureus (MRSA) poses a serious global health threat due to its multidrug resistance, complicating treatments in both human and veterinary medicine. The rising challenge of antimicrobial resistance necessitates alternative therapeutic strategies, including nanotechnology-based interventions. In this study, silver nanoparticles (AgNPs) were biosynthesized, optimized, and characterized using Acalypha godseffiana leaf extract, a medicinal plant native to Nigeria, serving as a natural reducing and stabilizing agent. Optimal synthesis was achieved using 1 mM AgNO₃ at 90 °C for 90 minutes with 1 mg/mL of plant extract. UV–Vis spectroscopy confirmed AgNP formation with a surface plasmon resonance peak at 432 nm. Scanning electron microscopy showed spherical, well-dispersed particles with an average diameter of 37 nm. In comparison, X-ray diffraction revealed a face-centered cubic crystalline structure with a mean crystallite size of 29 nm. Energy-dispersive X-ray spectroscopy detected elemental silver with a prominent signal at 3.0–3.2 keV. A zeta potential of −57.5 mV indicated excellent colloidal stability. FTIR analysis identified functional groups such as O–H and C=O, suggesting phytochemical involvement in particle stabilization. The biosynthesized AgNPs exhibited significant antibacterial activity against MRSA, yielding a maximum inhibition zone of 20.78 mm, a minimum inhibitory concentration (MIC) of 625 µg/mL, and a minimum bactericidal concentration (MBC) of 1250 µg/mL. This study is the first to report the anti-MRSA activity of A. godseffiana-derived AgNPs, underscoring their potential as eco-friendly and effective antimicrobial agents against resistant pathogens.