Biosynthesized nanoparticles (NPs) created through environmentally friendly and low-toxicity methods show great potential for various nanotechnology applications. In particular, copper nanoparticles (Cu-NPs) are promising for medical uses. This study aims to explore the eco-friendly synthesis of Cu-NPs and their potential as a novel strategy to combat antimicrobial resistance. Cu-NPs were synthesized using Ralstonia sp. KF264453 and characterized with techniques including ultraviolet–visible (UV–Vis) spectroscopy, feld emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), zeta potential analysis, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The antibacterial properties of the NPs and their synergistic effects with common antibiotics were assessed. The study also investigated their impact on bacterial cell membrane disruption, bioflm formation, efflux pump activity, and motility. UV–Vis analysis indicated a signifcant absorption peak at 552 nm, confrming surface plasmon resonance (SPR) for Cu-NPs. FESEM images revealed predominantly spherical NPs with an average size of 69.7 nm. DLS measurements indicated a hydrodynamic diameter of 78.2 nm due to stabilizing biomolecules. A zeta potential of - 5.1 mV suggested moderate colloidal stability, suitable for short-term biomedical applications. XRD analysis confrmed a face-centered cubic (FCC) crystalline structure with an average crystallite size of 45 nm. FTIR spectra detected functional groups, indicating that proteins, carbohydrates, lipids, and amino acids may have contributed to the synthesis and stabilization of the NPs. Cu-NPs showed notable antibacterial effcacy, with minimum inhibitory concentrations (MIC) between 0.625 and 5 μg/mL and minimum bactericidal concentrations (MBC) ranging from 5 to 20 μg/mL. They improved the effectiveness of penicillin and cefxime, enhanced membrane permeability, inhibited bioflm formation, disrupted efflux pump activity in Staphylococcus aureus SA-1199B, and decreased swarming motility in Pseudomonas aeruginosa. Cu-NPs demonstrate strong antimicrobial activity, inhibit bioflm formation and efflux pump function, and enhance the effectiveness of conventional antibiotics. While they show promise in combating antimicrobial resistance, further research is needed to assess their clinical potential and safety for medical use.
