Comparative Study of Silver, Gold, and Zinc Oxide Nanoparticles for Their Antimicrobial Activity and Cytotoxicity Against Cancer Cell Lines

Abstract

The rapid advancement of nanotechnology has positioned metallic nanoparticles as promising alternatives to conventional antimicrobial and anticancer agents. This review provides a comprehensive comparative analysis of silver (Ag), gold (Au), and zinc oxide (ZnO) nanoparticles, focusing on their synthesis strategies, physicochemical characteristics, antimicrobial efficacy, and cytotoxic potential against various cancer cell lines. Emphasis is placed on the influence of synthesis routes particularly green synthesis on particle morphology, stability, and biocompatibility, highlighting how phytochemical-mediated approaches enhance therapeutic performance while reducing toxicity. Among the three nanomaterials, Ag nanoparticles demonstrate the strongest broad-spectrum antimicrobial activity due to sustained Ag⁺ ion release and membrane disruption, while ZnO nanoparticles exhibit potent reactive oxygen species (ROS)-mediated antibacterial effects and notable selective cytotoxicity against cancer cells. Au nanoparticles, although relatively inert in antimicrobial applications, serve as highly effective drug delivery platforms and sensitizing agents in combination therapies. The review further discusses the mechanistic basis of anticancer activity, including oxidative stress induction, mitochondrial dysfunction, DNA damage, and activation of apoptotic signaling pathways such as p53 and caspase cascades. Comparative cytotoxicity data indicate that nanoparticle efficacy is strongly dependent on size, shape, dose, and surface functionalization, with smaller and biogenically synthesized particles generally exhibiting higher biological activity. Additionally, hybrid nanocomposites such as Ag/ZnO and Au/ZnO show synergistic effects, enabling enhanced antimicrobial and anticancer performance at reduced dosages. Despite their promising biomedical applications, challenges such as long-term toxicity, biodistribution concerns, and regulatory limitations remain significant barriers to clinical translation. Overall, this review underscores the potential of Ag, Au, and ZnO nanoparticles particularly in green-synthesized and hybrid forms as next-generation therapeutic agents for addressing multidrug-resistant infections and improving cancer treatment outcomes