Green Synthesized Ag@ZnO Bimetallic Nanoparticles from Couroupita guianensis: Superior Anticancer, Antioxidant, and Antibacterial Activities

This study addresses a critical challenge in nanomedicine: the development of sustainable and highly effective bio nanomaterials for diverse therapeutic applications. Conventional nanoparticle synthesis often relies on harsh chemicals, raising environmental and biocompatibility concerns. Here, we report an innovative green synthesis of silver-zinc oxide bimetallic nanoparticles (Ag@ZnONPs), utilizing the natural bio reductants and stabilizers inherent in Couroupita guianensis leaf Extract. Comprehensive characterization via UV–Vis, FTIR, XRD, TEM, and NTA confirmed the successful formation of highly crystalline, spherical Ag@ZnONPs, with a size of approximately 30 nm. The Ag@ZnONPs demonstrated significant antioxidant activity, achieving 72.2% DPPH scavenging at 10 μg/mL, comparable to ascorbic acid. Crucially, they exhibited potent broad-spectrum antibacterial efficacy against both Gram-positive (Staphylococcus aureus (IC₅₀: 38 μg/mL), Bacillus subtilis (IC₅₀: 36 μg/mL)) and Gram-negative (Escherichia coli (IC₅₀: 36 μg/mL), Salmonella typhi (IC₅₀:37 μg/mL)) bacterial strains. This antibacterial performance substantially surpassed that of the crude leaf extract and the standard antibiotic chloramphenicol, underscoring their potential in combating antimicrobial resistance. The in-vitro anticancer assessments, the Ag@ZnONPs induced a significant dose-dependent cytotoxic effect on Hep-G2 liver cancer cells, with a compelling IC₅₀ of 26.8 μg/mL, indicating a synergistic effect superior to the leaf extract alone (IC₅₀: 32.2 μg/mL). These findings position Couroupita guianensis-mediated Ag@ZnONPs as highly promising, multifunctional nontherapeutic agents with significant implications for addressing global health challenges in oxidative stress, infectious diseases, and oncology, contributing valuable insights to the field of sustainable nanotechnology.