Onion peel-mediated biosynthesis of TiO2-ZnO bimetallic nanoparticles: Antimicrobial, antibiofilm, and anticancer activities

Abstract

The rising challenges of antibiotic resistance and cancer necessitate the development of sustainable, cost-effective, and multifunctional therapeutic agents. This study introduces a green synthesis approach for bimetallic nanoparticles (BNPs) using agro-waste materials. For the first time, bimetallic titanium dioxide–zinc oxide (TiO 2 -ZnO) BNPs were synthesized using onion peel extract as a natural reducing and stabilizing agent. UV-Vis spectroscopy confirmed nanoparticle formation with a peak corresponding to a size of approximately 320 nm. DLS showed an average hydrodynamic diameter of 145.1 nm, and TEM revealed monodispersed nanoparticles, ranging from 80 to 150 nm. The BNPs exhibited broad-spectrum antimicrobial activity with MIC values of 500 μg/mL against Bacillus subtilis , Pseudomonas aeruginosa , and Candida albicans ; 1000 μg/mL against Staphylococcus aureus ; and 250 μg/mL against Escherichia coli . They also demonstrated significant antibiofilm activity against B. subtilis -MRSA with a 63.1% inhibition rate at 125 μg/mL. Additionally, TiO 2 -ZnO BNPs showed potent cytotoxic effects on MCF-7 breast cancer cells, with an IC 50 of 5.97 ± 0.37 μg/mL, and anticancer activity was mediated by caspase-8 activation and VEGFR-2 downregulation. This green-synthesized TiO 2 -ZnO BNPs offer a promising dual-function nanoplatform for combating microbial infections and cancer, highlighting the potential of sustainable nanotechnology for biomedical applications.