Curry Leaf Phytochemical-Mediated Synthesis of Magnetic Metal Oxide Nanomaterials with Enhanced Antimicrobial Properties

Abstract

With the increased demand for sustainable nanomaterials, research efforts have been directed towards developing green methods for their synthesis, which removes hazardous chemicals to improve the functional properties of nanomaterials. The magnetic metal oxide nanomaterials (MMONs) were synthesized using Murraya koenigii extract as a natural reducing, capping, and stabilizing agent in this study, which is an eco-friendly process. The phytochemicals contained in the curry leaf extract namely polyphenols, flavonoids, alkaloids and phenolic compounds, gave an excellent controlled synthesis of highly stable magnetic metal oxide nanoparticles with enhanced physicochemical properties. The synthesized nanomaterials were fully characterised using UV–Visible spectroscopy, Fourier Transform InfraRed Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDS), Vibrating Sample Magnetometry (VSM), and Thermogravimetric Analysis (TGA) and their crystalline structure, nanoscale morphology, elemental purity, thermal stability and superparamagnetic behaviour were confirmed. The antimicrobial activity of the synthesized magnetic metal oxide nanomaterials was tested using representative bacteria including Gram-positive and Gram-negative bacteria. The results showed that antibacterial activity was significantly improved, which is believed to be due to the synergistic effects of phytochemical functionalization on the surface of the nanoparticles, the reactive oxygen species (ROS) generation, disruption of bacterial cell membrane, and increased interaction of the nanoparticles with the microbial cells. The phytochemical coating helped to increase the antimicrobial activity and also increased the stability of the synthesized nanomaterials and its biocompatibility, which would enable the application of the synthesized nanomaterials in biomedical applications. In addition, their superior magnetic responsiveness allows for fast magnetic separation and potential reusability, facilitating their use in the medical field, environmental cleanup, antimicrobial coatings, water disinfection, and targeted therapeutic systems. In summary, the proposed synthesis method using phytochemicals offers a simple, low-cost, scalable and environmentally friendly way to synthesize multifunctional magnetic metal oxide nanomaterials with excellent antimicrobial activity. The work presented in this thesis helps towards the development of green nanotechnology combining sustainable synthesis and improved biological activity, with potential applications for next generation antimicrobial materials in biomedical, pharmaceutical and environmental applications.