Graphene oxide nanosheets disrupt lipid composition, Ca2+ homeostasis and synaptic transmission in primary cortical neurons

TL;DR

This study investigates how graphene oxide nanosheets affect primary cortical neurons, revealing disruptions in lipid composition, calcium homeostasis, and synaptic transmission, which are crucial for neural function and biomedical applications.

Contribution

It provides a comprehensive analysis of graphene oxide's effects on neurons, highlighting its impact on synaptic activity and calcium regulation, which was previously not well characterized.

Findings

GO causes inhibition of excitatory transmission

GO reduces excitatory synaptic contacts

GO induces autophagy and alters Ca2+ dynamics

Abstract

Graphene has the potential to make a very significant impact on society, with important applications in the biomedical field. The possibility to engineer graphene-based medical devices at the neuronal interface is of particular interest, making it imperative to determine the biocompatibility of graphene materials with neuronal cells. Here we conducted a comprehensive analysis of the effects of chronic and acute exposure of rat primary cortical neurons to few-layers pristine graphene (GR) and monolayer graphene oxide (GO) flakes. By combining a range of cell biology, microscopy, electrophysiology and omics approaches we characterized the graphene neuron interaction from the first steps of membrane contact and internalization to the long-term effects on cell viability, synaptic transmission and cell metabolism. GR/GO flakes are found in contact with the neuronal membrane, free in the cytoplasm and internalized through the endolysosomal pathway, with no significant impact on neuron viability. However, GO exposure selectively caused the inhibition of excitatory transmission, paralleled by a reduction in the number of excitatory synaptic contacts, and a concomitant enhancement of the inhibitory activity. This was accompanied by induction of autophagy, altered Ca2+ dynamics and by a downregulation of some of the main players in the regulation of Ca2+ homeostasis in both excitatory and inhibitory neurons. Our results show that, although graphene exposure does not impact on neuron viability, it does nevertheless have important effects on neuronal transmission and network functionality, thus warranting caution when planning to employ this material for neuro-biological applications.