Green-Synthesized Leucas aspera-Functionalized ZnO Nanoparticles for Antibacterial and Anticancer Biomedical Applications

Biogenic and bioactive nanomaterials synthesized through green approaches have gained considerable attention for therapeutic applications. In this study, zinc oxide nanoparticles (ZnO NPs) were successfully synthesized using an aqueous leaf extract of Leucas aspera as a natural reducing and capping agent to produce phytochemical-functionalized ZnO nanoparticles (LA-ZnO). The synthesized nanoparticles were characterized using UV-Vis, FTIR, XRD, SEM, EDX, and DLS analyses. UV-Vis spectra showed absorption peaks at 391 nm for ZnO and 313 nm for LA-ZnO, while XRD confirmed a hexagonal wurtzite structure with average crystallite sizes of 50.19 and 33.72 nm, respectively. SEM analysis revealed rod-like ZnO and flower-like LA-ZnO morphologies, and EDX confirmed Zn and O with trace carbon from phytochemical surface functionalization. DLS measurements indicated effective colloidal stabilization of LA-ZnO nanoparticles. The bioactive LA-ZnO exhibited concentration-dependent antibacterial activity against Gram-positive and Gram-negative bacteria, showing maximum inhibition against Staphylococcus aureus (18 mm at 2000 µg). In vitro MTT assays demonstrated cytotoxicity toward A549 and MCF-7 cancer cells with IC50 values of 22.55 and 81.15 µg/mL, respectively. These findings highlight Leucas aspera-mediated ZnO nanoparticles as promising biogenic nanomaterials for antimicrobial and therapeutic biomedical applications.