Green synthesis of nickel oxide nanoparticles using Hibiscus rosa-sinensis leaf extract: characterization, antimicrobial, antioxidant, and cytotoxicity properties

This study presents an inexpensive and eco-friendly method for the synthesis of Nickel Oxide Nanoparticles (NiO NPs) using Hibiscus rosa-sinensis leaf extract with aqueous solutions. It was characterized using several analytical techniques, including UV-Vis, FTIR, XRD, SEM-EDX mapping, and HR-TEM-SAED. The functional groups indicated metal-oxygen bonding, confirming the presence of NiO. The cubic cell shape of NiO was confirmed by the XRD pattern with an average crystallite size of 18 nm. The images of both FE-SEM and HR-TEM showed spherical-shaped nanoparticles in the range of 18-50 nm. The synthesized NiO NPs were subjected to an antimicrobial study using the Kirby-Bauer method against 6 different bacterial strains: B. subtilis, E. faecalis, S. aureus, E. coli, P. aeruginosa , and S. marcescens, and 3 different fungal strains: A. niger, C. albicans , and C. parapsilosis . The nanoparticles exhibit antimicrobial activity with an effective range of 62.5 to 500 nmol/disc. The IC 50 measured via the CUPRAC assay related to antioxidant activity was 326.9 µM, and the IC 50 from the MTT assay, concerning in vitro cytotoxicity against MCF 7 breast cancer cells, was 345.7 µg mL -1 . This reinforces the low cytotoxicity of the tested samples. The results show that H. rosa-sinensis-mediated NiO NPs have potential for biomedical applications due to their antimicrobial and antioxidant activities and good biocompatibility.