Efficacy of mycosynthesized zinc oxide nanoparticles against bacterial infections and oxidative stress

Biologically mediated zinc oxide nanoparticles (ZnO NPs) were synthesized from Aspergillus flavus extract and evaluated to check their antibacterial and antioxidant properties, particularly against Mycobacterium fortuitum and Serratia marcescens, two significant healthcare-associated pathogens. For this purpose, ZnO NPs were synthesized using the extracellular supernatant of A. flavus, where a pale white color was observed after 24 hrs, indicating successful nanoparticle formation. Various characterization techniques were employed to analyze the synthesized nanoparticles, where UV-Vis spectroscopy revealed a strong absorption peak at 375 nm, confirming ZnONP formation. Differential light scattering (DLS) analysis showed two peaks, one between 30–100 nm and another from 200–1000 nm, indicating size variation and possible aggregation. Fourier transform infrared (FTIR) spectroscopy displayed peaks at 3326 cm-1, 2990 cm-1, 2361 cm-1, 1640.07 cm-1, 1053.87 cm-1, and 547 cm⁻1, while scanning electron microscopy (SEM) confirmed spherical nanoparticles sized 30–100 nm. Our results demonstrated a significant antibacterial effect that increased with higher nanoparticle concentrations, where ZnO-NPs at 150 μg/disc showed inhibition zones of 22 mm against M. fortuitum and 13 mm against S. marcescens. In the reactive nitrogen assay, the IC50 values for ZnO NPs and gallic acid were found to be 130 μg/mL and 100 μg/mL, respectively, while in the reactive oxygen assay, ZnO NPs showed an IC50 value of approximately 115 μg/mL, comparable to that of gallic acid thus prooving that these NPs can effectively scavenge free radicals such as superoxide and nitric oxide. These findings suggest that ZnO NPs synthesized using A. flavus are not only environmentally friendly and non-toxic but also hold great promise as effective antimicrobial and antioxidant agents for potential biomedical applications.