Eco-Friendly Selenium Nanoparticle Strategy Against Staphylococcus Aureus Biofilm Formation.

Biological synthesis of nanoparticles provides an eco-friendly method for producing bioactive materials characterized by low toxicity and enhanced bioavailability. In this study, selenium nanoparticles (SeNPs) were synthesized using the viable cell filtrate of Staphylococcus haemolyticus. Biosynthesis with bacterial cell filtrate uses extracellular enzymes, proteins, and metabolites as reducing and capping agents to convert a selenium precursor (commonly sodium selenite, Na₂SeO₃) into elemental selenium nanoparticles (Se⁰). Advantages include mild conditions, eco-friendliness, and often improved biocompatibility. Characterized by UV-Vis spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), and zeta potential analysis. The antimicrobial potential of SeNPs was assessed against biofilm-forming Staphylococcus aureus using a microdilution MIC assay. The SeNPs exhibited broad-spectrum activity, effectively inhibiting Gram-positive and Gram-negative bacteria, as well as Candida species. They also demonstrated strong antioxidant activity and low cytotoxicity, highlighting their safety profile. Furthermore, synergistic assays revealed that combining SeNPs with conventional antimicrobials enhanced their inhibitory effects, including against multidrug-resistant strains. At the molecular level, the clfB gene was detected by PCR, and real-time PCR revealed significant modulation of its expression following SeNP treatment, suggesting interference with biofilm formation. Cytotoxicity assays further indicated that SeNPs exhibited low toxicity toward normal fibroblast (HdFn) cells while showing improved anticancer activity against PC3 cells compared to free drug or neat selenium nanoparticles.