Graphene nanoflakes for acute manipulation of membrane cholesterol and transmembrane signaling

Cholesterol is one of the most essential lipids in eukaryotic cell membranes. However, acute and selective manipulation of membrane cholesterol remains challenging. Here, we report that graphene nanoflakes (GNFs) insert into the plasma membrane and directly interact with cholesterol, resulting in acute cholesterol enrichment - and thus structural and functional changes. Using two representative cell preparations, we explore the utility of GNFs in modifying cell communication pathways sensitive to membrane cholesterol. In fibroblasts, GNFs enhance ATP-induced intracellular Ca2+-release by allosteric facilitation of P2Y receptors, a subtype of G protein-coupled receptors, in a cholesterol-dependent manner. In neurons, which possess higher membrane cholesterol levels than most cell types, GNFs further increase cholesterol. Consequently, GNFs change membrane fluidity, especially at synaptic boutons, and potentiate neurotransmitter release by accelerating synaptic vesicle turnover. Together, our results provide a molecular explanation for graphene9s cellular impacts and demonstrate its potential for membrane-oriented engineering of cell signaling.