Influence of oleic acid coating on the magnetic susceptibility and Fenton reaction-mediated ROS generation by the iron oxide nanoparticles

Fenton reaction-mediated reactive oxygen species (ROS) generation by the iron oxide nanoparticles (IONPs) is responsible for its antibacterial activity. In general, IONPs are surface-coated to facilitate stability, control over size, biocompatibility, solubility, etc. We hypothesize that the extent of surface coating onto the IONPs might affect Fenton reaction-mediated ROS generation, which would eventually impact its antibacterial activity. In the present study, IONPs were prepared using the co-precipitation method, and different weights of oleic acid (OA) were loaded onto the IONPs. Pristine IONPs and oleic acid-coated iron oxide nanoparticles (OA-IONPs) were characterized using Fourier transform-infrared spectroscopy, dynamic light scattering, transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry, goniometer, and thermogravimetric analysis. We found that magnetic susceptibilities of the IONPs were significantly enhanced with an increase in OA loading on the IONPs. The antibacterial study showed that the percentage inhibition was inversely related to the extent of oleic acid coating on the IONPs. The dependency of ROS generation on the extent of surface coating over IONPs was demonstrated using the 2’,7’-dichlorodihydrofluorescein diacetate (DCFDA) assay. Although pristine IONPs showed the least ROS generation, they exhibited maximum percentage inhibition of bacteria. This might be due to mechanical damage to the bacterial cells because of their crystalline nature. In vitro biocompatibility study conducted on L929 fibroblast cell lines indicated that all the nanoparticle preparations were cytocompatible. This study concluded that the extent of surface coating influences the Fenton reaction-mediated ROS generation and also the magnetic susceptibilities of the IONPs.