Synergistic effect of Indigofera cordifolia-mediated Cu–ZnO nanocomposites for antimicrobial, antioxidant, and hemocompatibility activities

The increasing prevalence of antimicrobial resistance and the environmental limitations of conventional nanoparticle synthesis highlight the need for sustainable and effective alternatives. In this study, copper-doped zinc oxide nanocomposites (Cu–ZnO NCs) were green-synthesized using Indigofera cordifolia leaf extract, which served as a reducing, stabilizing, and capping agent. The synthesized nanocomposites were comprehensively characterized using UV–Visible spectroscopy (200–280 nm), Fourier-transform infrared spectroscopy (400–3000 cm −1 ), X-ray diffraction (2θ range 30–40°), and transmission electron microscopy, confirming their crystalline structure and nanoscale size with an average particle diameter of 14.72 nm. The Cu–ZnO NCs exhibited significant antimicrobial activity. Strong antifungal efficacy was observed against A . niger , with prolonged inhibition up to 13 days at 750 μg/mL, surpassing the standard drug fluconazole (10 μg/mL). Broad-spectrum antibacterial activity was also demonstrated against Gram-positive ( Bacillus subtilis , Enterococcus faecalis , Staphylococcus aureus ) and Gram-negative ( Escherichia coli ) bacteria. The antimicrobial mechanism was further elucidated through reactive oxygen species (ROS) generation, protein leakage (Bradford assay), and lactate dehydrogenase (LDH) release assays, all of which confirmed concentration-dependent oxidative stress and membrane damage in bacterial cells. Additionally, the nanocomposites exhibited considerable antioxidant activity reaching 42.02% and 45.23% at 500 and 750 μg/mL respectively as determined by the DPPH free radical scavenging assay. Hemocompatibility analysis revealed that the Cu–ZnO NCs were non-haemolytic and safe toward erythrocytes up to 500 μg/mL. In conclusion, Indigofera cordifolia -mediated Cu–ZnO nanocomposites demonstrate promising physicochemical properties and multifunctional biological activities, supporting their potential application in antimicrobial therapy, biomedical formulations, and environmental remediation.