Biosynthesis of CuO-ZnO nanoparticles using Levilactobacillus brevis: implication in antibacterial, antioxidant, and anticancer activities

Nanoparticles are increasingly applied in biomedical and environmental fields. Among them, bimetallic nanoparticles, especially CuO-ZnO, offer unique properties such as enhanced biological activity, small size, biocompatibility, and low toxicity. Biosynthesis has recently gained attention as an environmentally benign alternative to traditional chemical methods. In this study, antibiofilm, antibacterial, antioxidant, and anticancer properties of CuO-ZnO bimetallic nanoparticles using lactic acid-probiotic Levilactobacillus brevis bacterium cell-free supernatant (CFS) were examined. Their physicochemical characteristics were evaluated using ultraviolet-visible spectroscopy (UV-Vis), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). The synthesized CuO-ZnO NPs exhibited antibacterial effects against six pathogenic strains, with MIC values between 1.25 and 10 mg/mL, and MBC = MIC for the L. brevis CFS. CuO-ZnO NPs indicated over 70% biofilm inhibition against S. aureus, E. faecalis, and L. monocytogenes. Antioxidant activity (RSA) was 80.24% for CuO-ZnO NPs and 58.05% for the L. brevis CFS. The CuO-ZnO nanoparticles exhibited significant anticancer activity against COR-L105 with IC₅₀ = 3.5 µg/mL, confirmed via MTT assay, apoptosis/necrosis analysis, ROS, and cell cycle arrest flow cytometry. These results highlight CuO-ZnO NPs as promising antibacterial, anticancer, and antioxidant agents.