Investigating the biosafety and toxicity of magnetic iron oxide nanoparticles in vitro and in vivo

Abstract

Nanoparticles (NPs) are promising tools for a broad range of clinical applications, including therapeutic purposes. The surfaces of NPs can be modified for targeted therapy and a controlled drug release can be achieved with NPs as drug carriers, which is particularly desirable in the treatment of cancer to reduce side effects. However, their biosafety is still of concern due to toxic effects exhibited by NPs. Furthermore, upon administration, NPs will unavoidably come into contact with blood serum proteins and cells of the innate immune system, which is the body’s first line of defence. This can result in unwanted clearance of NPs by phagocytic cells such as macrophages, thus reducing their therapeutic efficacy. Here, we aimed to investigate the intracellular fate and toxicity of starch coated fluorescent iron oxide nanoparticles (IONPs) in mouse macrophages by using immunohistochemistry and microscopy techniques. We show that different protein corona compositions on the surface of IONPs can influence their uptake and also show that IONPs can enter cells through more than one endocytic pathway, including macropinocytosis, by using different sized fluorescent dextran molecules as endocytic markers. Through cytokine profiling using qPCR and transcriptome profiling using RNA-sequencing, we investigated the cellular immunotoxicity of IONPs by identifying particular biomarkers and genes which are involved in inflammatory processes. IONP toxicity was studied in vivo using zebrafish (Danio rerio) embryos as animal models following microinjections of IONPs. Biodistribution of IONPs was studied with confocal microscopy. Macrophages were labelled by microinjecting a high molecular weight dextran to investigate uptake of IONPs by macrophages in vivo, which was low. IONPs accumulated mostly in the pericardium and liver at 5dpf and overall a low mortality rate was recorded.