Azadirachta indica (AI) leaf extract coated ZnO-AI nanocore–shell particles for enhanced antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA)

Abstract

With the rise in microbial resistance to traditional antibiotics and disinfectants, there is a pressing need for the development of novel and effective antibacterial agents. Two major approaches being adopted worldwide to overcome antimicrobial resistance are the use of plant leaf extracts and metallic nanoparticles (NPs). However, there are no reports on the antibacterial potential of NPs coated with plant extracts, which may lead to novel ways of treating infections. This study presents an innovative approach to engineer antibacterial NPs by leveraging the inherent antibacterial properties of zinc oxide NPs (ZnO NPs) in combination with Azadirachta indica (AI) leaf extract, resulting in enhanced antibacterial efficacy. ZnO NPs were synthesised by the precipitation method and subsequently coated with AI leaf extract to produce ZnO-AI nanocore–shell structures. The structural and morphological characteristics of the bare and leaf extract coated ZnO NPs were analysed by x-ray diffraction and field emission scanning electron microscopy, respectively. The presence of an AI leaf extract coating on ZnO NPs and subsequent formation of ZnO-AI nanocore–shell structures was verified through Fourier transform infrared spectroscopy and photoluminescence techniques. The antibacterial efficacy of both ZnO NPs and ZnO-AI nanocore–shell particles was evaluated against methicillin-resistant Staphylococcus aureus using a zone of inhibition assay. The results showed an NP concentration-dependent increase in the diameter of the inhibition zone, with ZnO-AI nanocore–shell particles exhibiting superior antibacterial properties, owing to the combined effect of ZnO NPs and the poly phenols present in AI leaf extract. These findings suggest that ZnO-AI nanocore–shell structures hold promise for the development of novel antibacterial creams and hydrogels for various biomedical applications.