Dextran-coated iron oxide nanoparticle-induced nanotoxicity in neuron cultures

Ryan P Badman,Jessica L Killian,Michelle D Wang,Thomas A Cleland,Fenghua Hu,Shanna L Moore,Tuancheng Feng

doi:10.1038/s41598-020-67724-w

Abstract

Recent technological advances have introduced diverse engineered nanoparticles (ENPs) into our air, water, medicine, cosmetics, clothing, and food. However, the health and environmental effects of these increasingly common ENPs are still not well understood. In particular, potential neurological effects are one of the most poorly understood areas of nanoparticle toxicology (nanotoxicology), in that low-to-moderate neurotoxicity can be subtle and difficult to measure. Culturing primary neuron explants on planar microelectrode arrays (MEAs) has emerged as one of the most promising in vitro techniques with which to study neuro-nanotoxicology, as MEAs enable the fluorescent tracking of nanoparticles together with neuronal electrical activity recording at the submillisecond time scale, enabling the resolution of individual action potentials. Here we examine the dose-dependent neurotoxicity of dextran-coated iron oxide nanoparticles (dIONPs), a common type of functionalized ENP used in biomedical applications, on cultured primary neurons harvested from postnatal day 0–1 mouse brains. A range of dIONP concentrations (5–40 µg/ml) were added to neuron cultures, and cells were plated either onto well plates for live cell, fluorescent reactive oxidative species (ROS) and viability observations, or onto planar microelectrode arrays (MEAs) for electrophysiological measurements. Below 10 µg/ml, there were no dose-dependent cellular ROS increases or effects in MEA bursting behavior at sub-lethal dosages. However, above 20 µg/ml, cell death was obvious and widespread. Our findings demonstrate a significant dIONP toxicity in cultured neurons at concentrations previously reported to be safe for stem cells and other non-neuronal cell types.

Highlights

Recent technological advances have introduced diverse engineered nanoparticles (ENPs) into our air, water, medicine, cosmetics, clothing, and food
To assess the safety of exposing the mammalian central nervous system (CNS) to dextran-coated iron oxide nanoparticles (dIONPs), we explored their effects on mature, primary mammalian neuron health, in terms of both cell viability and electrophysiological activity measured with planar microelectrode arrays (MEAs)[28]
The lack of a dose-dependent increase in reactive oxidative species (ROS) is qualitatively consistent with previous in vitro nanotoxicology studies in fibroblasts[19] suggesting that there is a threshold concentration of internalized dIONPs that leads to cell death, rather than cell death arising from excess ROS generation[38]

Summary

Introduction

Recent technological advances have introduced diverse engineered nanoparticles (ENPs) into our air, water, medicine, cosmetics, clothing, and food. There are several limited in vitro and in vivo results demonstrating that there may be detrimental long-term effects of dIONPs in organs beyond the liver[15,17,19,20], and iron accumulation is increasingly implicated in neurodegenerative diseases[17,21] because IONPs have almost molecular size, they have a high surface-to-volume ratio. Their reactivity is much higher than larger particles and their interactions with subcellular structures can change dramatically with just slight alterations in ENP shape or surface properties[22,23]. While progress has been made in optimizing low-toxicity IONP coatings for applications that do not require cell internalization, such as drug delivery[24,25] or vascular imaging[26], challenges remain in synthesizing safe coatings on IONPs for applications that require neuronal cell uptake for long-term labeling[15]

Methods

Results

Conclusion