Surface carboxylation of iron oxide nanoparticles brings reduced macrophage inflammatory response through inhibiting macrophage autophagy

Macrophage autophagy is a common biological response triggered by nanomaterials, which is closely related to the regulation of inflammation. Superparamagnetic iron oxide (SPIO) nanoparticles have been used for study of autophagy response due to their broad biomedical applications. However, few reports have focused on how to regulate the macrophage autophagy response induced by SPIO nanoparticles. In this study, SPIO nanoparticles grafted with carboxyl groups were synthesized and for the comparison of macrophage autophagy with unmodified nanoparticles. The study on the correlation between autophagy and inflammation induced by the two kinds of SPIO nanoparticles was also included, and the one that grafted with carboxyl groups shows a reduction of autophagy and thereby caused a milder inflammatory response. We proposed that the increased amount of albumin adsorption on the surface of carboxylated SPIO nanoparticles, a protein previously proven to attenuate autophagy, can be considered an important reason for reducing autophagy and inflammation. In general, the carboxyl modification of SPIO nanoparticles has been demonstrated to reduce inflammation by inhibiting macrophage autophagy, which may provide some insights for the design of nanomaterials in the future.