Antimicrobial potency and biocompatibility of biogenic selenium nanoparticles by Prosopis farcta

Selenium nanoparticles (SeNPs) have attracted increasing attention as promising antibacterial agents, however the antibacterial performance and mechanisms of biosynthesized SeNPs remain insufficiently understood. This study reports a novel green synthesis of SeNPs using an extract from ripe fruits of the Iraqi Prosopis farcta plant and evaluates their antimicrobial activity and biocompatibility toward normal human dermal fibroblasts (HDFa cells). The synthesis was carried out using infrared (IR) irradiation. The synthesized SeNPs were characterised by FE-SEM, EDX, XRD, UV-Vis, FTIR, particle size distribution, and zeta potential analyses. Successful reduction of Se⁴⁺ to elemental Se⁰ and stabilization by P. farcta extract were confirmed by a distinct colour change of colloidal solutions under desirable synthesis conditions. IR-synthesized SeNPs were mainly spherical, with a smaller average hydrodynamic size of 25.43 nm and a higher zeta potential of -26.5 mV, indicating greater colloidal stability. FTIR analysis indicated that phenolic compounds from the plant extract were preserved in IR-synthesized SeNPs but partially degraded during heating, demonstrating the superior core-shell integrity achieved through IR synthesis. Antimicrobial activity was assessed against Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis), Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae), and the fungus Candida albicans. All tested strains were susceptible to SeNPs, with inhibition zone diameters ranging from 0.00 ± 0.00 to 29.3 ± 2.9 mm. Staphylococcus aureus showed the highest bacterial sensitivity, while Candida albicans also demonstrated considerable antifungal activity. The biosynthesized SeNPs exhibited strong, broad-spectrum antimicrobial activity against clinically relevant Gram-positive and Gram-negative bacteria, as well as the fungal pathogen Candida albicans. Notably, the nanoparticles remained effective against multidrug-resistant (MDR) clinical isolates, highlighting their potential as alternative antimicrobial agents in an era of growing antibiotic resistance. In terms of biocompatibility, the SeNPs showed low cytotoxicity toward normal human dermal fibroblasts (HDFa) at concentrations up to 512 μg/mL, with cell viability exceeding 80%. This favorable safety profile, combined with their potent antimicrobial activity, supports the potential application of P. farcta-derived SeNPs in wound healing, antimicrobial coatings, or topical formulations.