Green Synthesis of Selenium Nanoparticles using Juglans regia Leaf Extract with Anti-MRSA Activity

Abstract

The global rise of drug-resistant pathogens, particularly methicillin-resistant Staphylococcus aureus (MRSA), highlights the urgent need for novel antimicrobial therapy. This study aimed to biosynthesize selenium nanoparticles (SeNPs) using walnut (Juglans regia) leaf extract and evaluate their antibacterial activity against molecularly characterized MRSA isolates from human and animal sources. The synthesized SeNPs were characterized by UV-Vis spectroscopy, zeta potential analysis, scanning electron microscopy (SEM), and X-ray fluorescence (XRF). SEM analysis showed predominantly spherical particles with diameters ranging from 31 to 110 nm. Zeta potential analysis showed a surface charge of –9.42 mV. XRF results confirmed the presence of selenium element. Antibacterial activity was evaluated in vitro against 50 MRSA isolates (23 from humans and 27 from animals) using agar well diffusion and broth microdilution MIC assays. Animal-derived MRSA isolates were more susceptible to SeNPs than human derived MRSA isolates: with a higher proportion producing inhibition zones ≥ 20 nm (52% vs 30%). In addition, the lowest observed MIC for animal isolates was 583 µg/mL compared with 1166 µg/mL for human isolates. Cross tabulation demonstrated a statistically significant difference in susceptibility between animal and human isolates (Fisher’s exact test, p = 0.042). These in vitro results indicate walnut leaf mediated SeNPs possess antibacterial activity against MRSA; thus, could be tested for further mechanistic, cytotoxicity and in vivo studies prior to potential clinical application.