Unveiling the structural dynamics and anticancer potential of zinc and iron oxide nanoparticles derived from Allium cepa peels

This study focuses on synthesizing iron and zinc oxide nanoparticles (IO NPs/ZnO NPs) using Allium cepa (red onion skin extract, ROSE). The aqueous extract from A. cepa was analyzed using LC-MS to identify key phytochemicals, which were used to synthesize IO NPs/ZnO NPs. These NPs were characterized by UV-visible, SEM, EDX, XRD, FT-IR and DLS techniques. The nanoparticles were found to be polycrystalline, mono to poly-disperse, and spherical with average sizes of 55 nm for IO NPs and 56 nm for ZnO NPs. The IO NPs showed strong antimicrobial activity against Salmonella typhi, while ZnO NPs were more effective against Staphylococcus aureus. The ZnO NPs exhibited superior antioxidant activity (57.057% at 150 μg mL⁻¹) and brine shrimp lethality (LC₅₀ of 42.77 μg mL⁻¹) compared to IO NPs. In a similar pattern, ZnO NPs exhibited low hemolysis (%) and proved to be compatible with human RBCs. Zeta potential measurements indicated moderate stability, with values of −18.7 mV for IO NPs and −20.4 mV for ZnO NPs depicting moderate stability and poor flocculation for ZnO NPs. The ZnO NPs demonstrated better anticancer activity than IO NPs against HT29 cells (IC₅₀ of 86.95 μg mL⁻¹) and showed higher effectiveness against HepG2 cells (IC₅₀ of 68.01 μg mL⁻¹). Flow cytometry results indicated that ZnO NPs induced higher early and late apoptotic rates in cancer cells. Additionally, ZnO NPs showed greater biocompatibility with human RBCs, suggesting better potential for biomedical applications.