Membrane cholesterol mediates the cellular effects of monolayer graphene substrates

Abstract

Graphene possesses extraordinary properties that promise great potential in biomedicine. However, fully leveraging these properties requires close contact with the cell surface, raising the concern of unexpected biological consequences. Computational models have demonstrated that graphene preferentially interacts with cholesterol, a multifunctional lipid unique to eukaryotic membranes. Here we demonstrate an interaction between graphene and cholesterol. We find that graphene increases cell membrane cholesterol and potentiates neurotransmission, which is mediated by increases in the number, release probability, and recycling rate of synaptic vesicles. In fibroblasts grown on graphene, we also find an increase in cholesterol, which promotes the activation of P2Y receptors, a family of receptor regulated by cholesterol. In both cases, direct manipulation of cholesterol levels elucidates that a graphene-induced cholesterol increase underlies the observed potentiation of each cell signaling pathway. These findings identify cholesterol as a mediator of graphene’s cellular effects, providing insight into the biological impact of graphene.

Impact of Graphene on the Efficacy of Neuron Culture Substrates

“…Other studies examining the physiology of neurons cultured on graphene have found a potentiation of neurotransmission through increased presynaptic vesicle number, release probability, and turnover rate. [55] Graphene producing an increase in presynaptic neurotransmission could lead to increased postsynaptic cation channel activity, which is consistent with our thallium flux results on graphene-integrated platforms.…”

“…This reduction in cation channel expression could arise from a myriad of alterations, including transcription, translation, protein trafficking, and membrane structure. [55] Despite differences in ion channel representation, analysis of overall inward and outward current profiles revealed no significant difference between RGCs cultured on substrate-only or graphene-integrated platforms, indicating that graphene overlay does not alter the overall biophysical properties of RGCs. This is supported by previous studies showing that neurons cultured on graphene substrates do not show significantly altered electro-physiological properties, compared to neurons cultured on traditional culture substrates.…”

An Increase in Membrane Cholesterol by Graphene Oxide Disrupts Calcium Homeostasis in Primary Astrocytes

“…From a mechanistic standpoint, two nonmutually exclusive scenarios are possible: i) cholesterol may be attracted from other districts of the membrane to the point of contact with GNMs. This would stimulate further cholesterol synthesis, thus increasing the overall cellular cholesterol content; ii) GNMs might bind cholesterol present in the cell medium and carry it into cell membrane at the site of contact . Our LC‐MS analysis provided data for individual cholesteryl esters species, clearly indicating that the whole cholesterol metabolism is upregulated, including its esterification with fatty acids.…”

“…Interestingly, and in line with our findings, increased membrane cholesterol levels have been recently reported in primary neurons and cell lines grown onto to graphene substrates. Remarkably, cholesterol was the principal mediator of the cellular and physiological alterations induced by graphene on the overlying cell cultures . The cellular mechanisms mediating the interaction between GNMs and membrane cholesterol are of high interest, but still incompletely understood.…”

3D electronic and photonic structures as active biological interfaces

“…Biointerfaces, which are defined as the interfaces between biological systems and synthetic materials, act as an interdisciplinary area to explore biological science and clinical applications. In past decades, micro‐, nano‐, and mesoscale structural biointerfaces have been designed and formed by transforming synthetic materials into various geometries, including zero‐dimensional (0D), one‐dimensional (1D), two‐dimensional (2D), and three‐dimensional (3D) configurations . Due to their cellular and subcellular size, low‐dimensional (0D, 1D, and 2D) materials and structures present particular physical and chemical characters pertinent to biological systems, promoting their usages for revolutionary biological studies as functional biointerfaces .…”