Biogenic and green approach for ZnO nanoparticle synthesis via Bacillus licheniformis and their antimicrobial and anticancer potential

Microbial synthesis of nanoparticles has gained attention as an eco-friendly, efficient, and cost-effective alternative to conventional chemical and physical approaches. This study reports the biosynthesis of Zinc Oxide nanoparticles (ZnO NPs) through the use of the cell-free extract of Bacillus licheniformis strain FC14167, isolated from soil. The ZnO nanoparticles obtained in this study were characterized using a combination of UV–visible spectroscopy, FTIR, XRD, SEM–EDX, and TEM to assess their optical, structural, and morphological properties. ZnO nanoparticles showed a distinct UV-Vis apeak at 331 nm, FTIR analysis revealed functional groups contributing to nanoparticle synthesis, while XRD patterns verified the crystalline structure and purity. The ZnO NPs exhibited a well-defined hexagonal shape, averaging 36 nm in diameter, evident from SEM and TEM micrographs, and the presence of Zn was confirmed through the EDX spectral analysis. Biosynthesized ZnO NPs were found to possess effective antimicrobial activity and zones of inhibition against certain bacterial and fungal pathogens. Furthermore, the nanoparticles demonstrated cytotoxicity against HT-29 cancer cell lines, resulting to considerable necrotic and abnormal shapes in cancer cells with an IC₅₀ value determined to be 56.55 µg/mL. The current investigation indicates, biosynthesized ZnO NPs possess substantial anticancer activity and inhibitory effects against HT-29 cancer cell lines. Accordingly, this study conjectures the potential of bacteria-mediated ZnO NPs as effective anticancer agents.