Selenium nanoparticles functionalized with bacitracin: a novel approach for combating multidrug-resistant bacteria and evaluating lymphocyte response.

Green synthesis of nanoparticles has emerged as a promising approach to develop cost-effective, biocompatible, and environmentally friendly antimicrobial agents. In this study, we investigated the biosynthesis of selenium nanoparticles (SeNPs) using bacitracin-like inhibitory substances (BLIS) derived from Acinetobacter baumannii. We evaluated their antimicrobial, antibiofilm, and anticancer potential against multidrug-resistant (MDR) pathogens. The synthesized SeNPs were characterized using spectroscopic and imaging techniques, confirming their nanoscale size, hexagonal morphology, surface roughness, and a characteristic absorption peak at 270 nm. Antimicrobial activity was assessed against clinically isolated MDR bacteria and fungi, in which SeNPs demonstrated significant growth inhibition, with a minimum inhibitory concentration (MIC) of 250 mg/mL. Biofilm formation among Acinetobacter baumannii isolates showed variable biofilm-producing capacities, and treatment with SeNPs effectively reduced biofilm formation. Furthermore, gene expression analysis revealed significant downregulation of the mexB efflux pump gene in Pseudomonas aeruginosa following SeNP treatment, indicating a potential mechanism for overcoming antimicrobial resistance. Cytotoxicity evaluation using human lymphocytes demonstrated that SeNPs exhibited minimal toxicity, supporting their biocompatibility. In addition, the nanoconjugate system showed notable anticancer activity against the tested cancer cell lines. In conclusion, BLIS-mediated SeNPs represent a promising multifunctional nanoplatform with potent antimicrobial activities, alongside low cytotoxicity toward normal human cells. These findings highlight their potential application in combating MDR infections and advancing nanomedicine-based therapeutic strategies.