Cellular internalization and detailed toxicity analysis of protein-immobilized iron oxide nanoparticles

Iron oxide nanoparticles (IONPs) have been extensively used for biomedical applications like in the diagnosis and treatment of various diseases, as contrast agents in magnetic resonance imaging, and in targeted drug delivery. Despite several attempts, there is a dearth of information with respect to the cellular response and in-depth toxicity analysis of the nanoparticles. Considering the potential benefits of IONPs, there is a need to study the potential cellular damage associated with IONPs. The size and surface of the particles are some critical factors that should be analyzed when evaluating cytotoxicity. Therefore, in this study, we synthesized and characterized bare (7-9 nm) and protein-coated IONPs of diameter 50-70 nm, and evaluated their toxicity on membrane integrity, intracellular accumulation of reactive oxygen species, and mitochondrial activity in mouse fibroblast cell line by lactate dehydrogenase, 2',7'-dichlorofluorescein diacetate, and [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] (MTT) assays, respectively. Our extensive cytotoxicity analysis demonstrated that the size of the IONPs and their surface coating are the critical determinants of cellular response and potential mechanism toward cytotoxicity. The study of the interactions and assessment of potential toxicity of the nanoparticles with cells/tissues is a key determinant when considering their translation in biomedical applications.