Cell type-specific response to high intracellular loading of polyacrylic acid-coated magnetic nanoparticles

Abstract

Magnetic nanoparticles (NPs) are a special type of NP with a ferromagnetic, electron-dense core that enables several applications such as cell tracking, hyperthermia, and magnetic separation, as well as multimodality. So far, superparamagnetic iron oxide NPs (SPIONs) are the only clinically approved type of metal oxide NPs, but cobalt ferrite NPs have properties suitable for biomedical applications as well. In this study, we analyzed the cellular responses to magnetic cobalt ferrite NPs coated with polyacrylic acid (PAA) in three cell types: Chinese Hamster Ovary (CHO), mouse melanoma (B16) cell line, and primary human myoblasts (MYO). We compared the internalization pathway, intracellular trafficking, and intracellular fate of our NPs using fluorescence and transmission electron microscopy (TEM) as well as quantified NP uptake and analyzed uptake dynamics. We determined cell viability after 24 or 96 hours’ exposure to increasing concentrations of NPs, and quantified the generation of reactive oxygen species (ROS) upon 24 and 48 hours’ exposure. Our NPs have been shown to readily enter and accumulate in cells in high quantities using the same two endocytic pathways; mostly by macropinocytosis and partially by clathrin-mediated endocytosis. The cell types differed in their uptake rate, the dynamics of intracellular trafficking, and the uptake capacity, as well as in their response to higher concentrations of internalized NPs. The observed differences in cell responses stress the importance of evaluation of NP–cell interactions on several different cell types for better prediction of possible toxic effects on different cell and tissue types in vivo.

Keywords:

• intracellular fate
• transmission electron microscopy
• uptake quantification
• ROS
• cell viability

Acknowledgments

The authors would like to thank Nanotesla Institute Ljubljana for their technical support in the preparation of nanoparticles, Mojca Benčina, PhD, from the National Institute of Chemistry Slovenian for her help with fluorescence microscopy, and the team from the Institute of Cell Biology, Faculty of Medicine (University of Ljubljana) for the help with transmission electron microscopy. This work was supported by Slovenian Research Agency within projects J4-4324, J2-6758, Young Researchers Program, and MRIC UL IP-0510 Infrastructure Program.

Disclosure

The authors report no conflicts of interest in this work.