Green Synthesis and Pharmaceutical Applications of Metallic Nanoparticles: A Comprehensive Review

Abstract

In recent decades, nanotechnology has emerged as a revolutionary discipline with profound implications for the biomedical and pharmaceutical sectors. Among various nanomaterials, metallic nanoparticles (MNPs), including gold (Au), silver (Ag), zinc oxide (ZnO), and copper oxide (CuO), have garnered substantial interest due to their unique physico-chemical, optical, electrical, and catalytic properties. Traditional physical and chemical modalities of synthesized nanoparticles often carry significant drawbacks, such as the deployment of highly toxic reducing agents, substantial environmental toxicity, and exorbitant operational expenditures. Consequently, the paradigm of 'Green Synthesis' has arisen as a sustainable, ecofriendly, cost-effective, and safe alternative. This review provides an exhaustive and critical evaluation of the green synthesis protocols utilizing diverse biological entities, including plant extracts (leaves, roots, bark), macro/microalgae, fungi, and bacterial strains. It delineates the underlying mechanistic pathways of bioreduction, wherein primary and secondary metabolites like polyphenols, flavonoids, terpenoids, proteins, and polysaccharides function simultaneously as reducing, capping, and stabilizing agents. Furthermore, this paper provides a comprehensive overview of the pharmaceutical applications of these biogenic nanoparticles. Specifically, we explore their potent antimicrobial, antifungal, antiviral, anticancer, antioxidant, and anti-inflammatory activities, alongside their emerging role as highly selective targeted drug delivery vehicles anddiagnostic contrast agents. The paper also systematically reviews the criticalcharacterization methodologies essential for confirming synthesis, such asUV-Vis spectroscopy, XRD, FTIR, DLS, SEM, and TEM. Finally, currentchallenges, including toxicity profiles, polydispersity, regulatory bottlenecks,and scale-up constraints, are addressed, providing a strategic roadmap for future clinical translation. EYWORDS: Green Synthesis; Metallic Nanoparticles; Bioreduction;Antimicrobial Activity; Anticancer Therapeutics; Drug Delivery Systems;Biogenic Nanotechnology.