Eco-friendly synthesis of Ag/ZnO nanocomposite using Coleus amboinicus: Structural characterization and evaluation of antibacterial and anticancer activities

The pursuit of eco-friendly nanomaterials with both antibacterial and anticancer properties is gaining momentum in biomedical research. This study reports the green synthesis of Silver and Zinc oxide (Ag/ZnO) nanocomposite using Coleus amboinicus leaf extract as a natural reducing and stabilizing agent. Characterization via UV–Vis spectroscopy revealed absorption peaks at approximately 280 nm and 370 nm, indicative of Ag and ZnO nanoparticles, respectively. FTIR analysis identified phytochemical-derived functional groups responsible for particle stabilization, while SEM imaging showed agglomerated nanoparticles with diameters ranging from 100 to 150 nm. XRD analysis confirmed the crystalline nature of the nanocomposites. The biosynthesized Ag/ZnO nanocomposite exhibited potent antibacterial activity against multidrug-resistant strains including Enterococcus faecalis , Pseudomonas aeruginosa , MRSA, and Klebsiella pneumoniae , with significant zones of inhibition observed at a concentration of 80 μg/mL. Furthermore, the nanocomposite displayed promising anticancer activity against A549 lung cancer cells, achieving an IC₅₀ of 60 μg/mL after 24 h, as determined by MTT assay. Morphological features of apoptosis, such as membrane blebbing and nuclear condensation, were observed, while AO/EtBr, DCFDA, and Rhodamine 123 staining confirmed elevated reactive oxygen species (ROS) generation and disruption of mitochondrial membrane potential. These findings suggest a ROS mediated mechanism underlying the dual antibacterial and anticancer activities of the Ag/ZnO nanocomposite. This green synthesis approach provides a sustainable strategy for developing multifunctional nanomaterials, although further in vivo studies are required to confirm efficacy and elucidate the molecular mechanisms involved for future therapeutic applications.