Exploring the catalytic, bactericidal, and anticancer potential of Ag0, Au0, and Ag0@Au0 nanoparticles: A comparative study

Abstract

Societies still struggle with the pressing need to obtain novel, non-toxic, efficacious, and sustainable nanoparticles endowed with catalytic and biomedical potential. In light of this, we used the historically significant medicinal plant (Combretum glutinosum) to synthesize AgNPs, AuNPs, and their corresponding Ag⁰-Au⁰ alloy (Ag@Au). UV-Vis confirmed the syntheses by exposing their surface plasmon resonance peaks at 406 nm (Cg.AgNPs), 546 nm (Cg.AuNPs), and 516 nm (Cg.Ag@AuNPs). The biomolecules that mediated the synthesis were identified through phytochemical screening and confirmed by FTIR. FESEM, SEM, and TEM unveiled their morphologies as spherical for Cg.AgNPs, and Cg.Ag@AuNPs, whereas Cg.AuNPs showed multiple morphologies. DLS unveiled non-uniform size distributions with a mean value of 27.86 nm for Cg.AgNPs and 45.2 nm for Cg.AuNPs and EDX probed their elemental constituents, while their average crystallite sizes, lattices constant, interplanar distances, and other parameters were determined by PXRD analysis. The synthesized nanoparticles exhibited extra stability and remarkable catalytic action in the conversion of the substrate (4-nitrophenol) to the product (4-aminophenol). The catalytic rate was calculated for each sample and found to be 0.126±0.0021 (Cg.AgNPs), 0.1044±0.00271 (Cg.AuNPs), and 0.0809±0.00145 (Cg.Ag@AuNPs), and catalytic efficiency of 91.12 %, 80.05 %, and 90.87 %, respectively. The robust catalytic action is a result of high surface area which was found to be 105,984.96 m²/Kg and 44,693.46 m²/Kg for Cg.AgNPs, 61,820 m²/Kg and 10,530 m²/Kg for Cg.AuNPs, 73,850 m²/Kg and 19,830 m²/Kg for Cg.Ag@AuNPs, as calculated from the generated PXRD and TEM data, respectively. These nanoparticles are also bactericidal with minimum inhibition concentrations of 50 µg over Pseudomonas aeruginosa and Staphylococcus aureus. Additionally, they exhibited a cytotoxic effect against cancer cells of the lungs (A549), with 74.1, 63.7, and 48.7 μg per ml as the IC₅₀ values for Cg.AgNPs, Cg.AuNPs, and Cg.Ag@AuNPs, respectively. The outcomes of this study suggest that the green synthesized nanoparticles could be used as nanocatalysts that can potentially degrade 4-nitrophenol, and other related organic contaminants, and at the same time bactericidal against pathogenic microbes present in contaminated water bodies, and cytotoxic to cancer cell lines especially A549.