Ecofriendly production of CuO/ZnO nanocomposites from guava leaf biomass and their antimicrobial and selective anticancer activities

Psidium guajava leaf extract was utilized to produce CuO NPs and CuO/ZnO nanocomposites in this work. X-ray diffraction patterns showed the proper phase of the synthesized sample, and using Scherrer’s equation, the mean crystallite sizes were calculated to be 13.05 nm and 13.07 nm for CuO nanoparticles (NPs) and CuO/ZnO nanocomposite, respectively. From transmission electron microscopy images and particle size distribution from ImageJ, the samples had larger sizes of 84.6 nm and 96.6 nm, respectively. Fourier transform infrared (FTIR) spectroscopy also indicated the successful fabrication of the CuO NPs and CuO/ZnO nanocomposite, as the IR spectrum showed peaks at 611 and 521 cm⁻¹ for Cu–O and Zn–O, respectively. The biological activities were found to be higher for the CuO/ZnO nanocomposite than the CuO NPs alone. The inhibition zones recorded were 28 mm and 25 mm for Bacillus. subtilis and Staphylococcus aureus, respectively, followed by 24 mm and 21 mm for Salmonella typhi and Klebsiella pneumoniae, respectively. The nanocomposite exhibited selective cytotoxicity properties because the IC₅₀ values for Wi38 (normal human fibroblast cells) and SKOV3 (human ovarian carcinoma cells) were 295.48 and 81.87 µg/mL, respectively. Antioxidant analysis of (2,2-diphenyl-1-picrylhydrazyl) (DPPH) radical scavenging activity was found to be 6.93 µg/mL for the nanocomposite.