Comparative evaluation of Abrus precatorius mediated ZnO and CeO2 nanoparticles for biological applications

The green synthesis of metal oxide nanoparticles (NPs) using plant extracts has become popular as an environmentally sustainable alternative to conventional synthesis methods, but little comparative research is available on the plant-mediated synthesis of zinc oxide nanoparticles (ZnO NPs) and cerium dioxide nanoparticles (CeO 2 NPs) using Abrus precatorius leaf extract. This study was, therefore, designed to synthesize, comparatively characterize and screen the multifunctional biological activities of ZnO and CeO 2 NPs utilizing A. precatorius leaf extract as a dual reducing and stabilizing agent. The synthesized NPs were characterized in detail and their antioxidant, antibacterial, cytocompatibility and wound-healing characteristics were evaluated. Comprehensive characterization indicated successful creation of highly crystalline, thermally stable nanostructures with average particle sizes of 36 nm for ZnO and 22.6 nm for CeO2 NPs and optical band gap energies of 3.31 eV and 3.54 eV, respectively. Biological investigation showed that CeO₂ NPs had better antioxidant activity (IC 50 = 19 µg/mL) than ZnO NPs (IC 50 = 27 µg/mL), whereas ZnO NPs exhibited better antibacterial activity, especially against Gram-positive pathogens. ZnO NPs exhibited zones of inhibition of 12.0 ± 0.96 mm against Enterococcus faecalis at 1000 µg/mL, 11.0 ± 0.50, 12.0 ± 0.58, and 14.0 ± 0.45 mm against Streptococcus mutans, and 12.0 ± 0.56, 16.0 ± 0.63, and 18.0 ± 0.57 mm against Staphylococcus aureus at 250, 500, and 1000 µg/mL, respectively. Both NPs showed good cytocompatibility towards human embryonic kidney (HEK-293) cells with 55.0 ± 0.55% and 70.0 ± 0.60% cell viability at 200 µg/mL for ZnO and CeO2 NPs, respectively. ZnO NPs were further examined for wound healing based on their balanced antibacterial activity and cytocompatibility and greatly enhanced the wound closure in NCTC clone 929 (L929) fibroblast cells. In general, the present study relates the physicochemical properties to the biological performance of plant-mediated ZnO and CeO₂ NPs in a clear-cut manner. The comparative evaluation discussed in this paper generally improves the understanding of plant-mediated metal oxide NPs and gives useful insights for the selection of optimal nanomaterials for particular biomedical applications. These results provide a durable comparative basis for sensible selection and future development of plant-mediated metal oxide NPs for biomedical applications.