Antimicrobial properties of green synthesized copper nanoparticles

Background and objectives: With the increasing prevalence of bacterial resistance, multidrug-resistant (MDR) infections have become a significant challenge. Consequently, the treatment of bacterial infections has become increasingly important. In response, targeted therapeutic strategies to combat pathogenic bacteria have emerged. Metal nanoparticles, particularly copper nanoparticles, offer a promising alternative to antibiotics due to their antimicrobial properties and are being explored as a potential solution. Materials and methods: Copper nanoparticles were synthesized using a cell-free extract of Ralstonia sp. SM۸ and copper nitrate as a precursor. UV spectroscopy confirmed successful synthesis. The nanoparticles were characterized using field emission scanning electron microscopy (FESEM) for morphology, energy-dispersive X-ray spectroscopy (EDX) for elemental analysis, dynamic light scattering (DLS) for size distribution and colloidal stability, zeta potential analysis for surface charge, X-ray diffraction (XRD) for crystal structure, and Fourier-transform infrared spectroscopy (FT-IR) to investigate interactions with bacterial biomass. Finally, the antimicrobial activity of the copper nanoparticles was evaluated. Results and discussion: FESEM and EDX analyses revealed spherical nanoparticles with an average size of ۶۹ nm. DLS analysis confirmed a hydrodynamic diameter of ۷۸.۲ nm with a polydispersity index (PDI) of ۰.۳۸, indicating good colloidal stability, supported by a zeta potential of -۵.۱ mV. UV-Vis spectroscopy exhibited a peak at ۵۵۲ nm. FT-IR analysis suggested a role for proteins in nanoparticle shape and stabilization. The antimicrobial activity of CuNPs increased with concentration as demonstrated by the disk diffusion test. MIC values ranged from ۰.۱۶ to ۰.۳۳ μg/ml. CuNP concentrations at half the MIC (MIC/۲) inhibited biofilm formation in Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Pseudomonas aeruginosa. Moreover, these concentrations disrupted bacterial cell walls, inhibited bacterial motility, and interfered with Staphylococcus aureus efflux pumps. Notably, CuNPs exhibited synergistic effects with penicillin and cefixime antibiotics. These findings suggest that biosynthesized CuNPs can overcome multiple bacterial resistance mechanisms.

کلیدواژه ها:

Cu nanoparticle ، Antibiotic resistance ، Antibacterial activity ، Bacterial biofilm ، Synergy with antibiotics