Study of the interaction between graphene oxide and cholesterol using different artificial membrane models

Graphene Oxide (GO), the hydrophilic derivative of graphene, has attracted growing attention in nanomedicine due to its ability to interact with lipid membranes and modulate their physico-chemical properties. Its amphiphilic character and high density of oxygen-containing functional groups enable strong interactions with phospholipids and cholesterol, two key components that regulate membrane fluidity, permeability and structural integrity. In this work, we investigated the effect of GO on artificial membrane models, comprising liposomes and droplet interface bilayers (DIBs), composed by cholesterol and 1,2-dioleoyl-sn-glycero-3-phosphocoline (DOPC). A multidisciplinary approach combining fluorescence leakage assays, differential scanning calorimetry, nuclear magnetic resonance, Raman and fluorescence spectroscopy, and water permeability studies was employed. Results demonstrated that GO alters bilayer organization by weakening lipid-lipid interactions, lowering phase transition cooperativity, and increasing bilayer fluidity and permeability. NMR quantification revealed a significant reduction in the DOPC:Chol ratio, consistent with cholesterol displacement or redistribution within the bilayer. Fluorescence analysis using Filipin III further indicated an increased cholesterol exposure at the outer leaflet, suggesting sterols reorientation in the presence of GO. These effects were observed without complete vesicle disruption, highlighting a remodeling rather than a destructive action. Compared to methyl-β-cyclodextrin (MβCD), the gold standard cholesterol extractor, GO induced more profound changes by simultaneously promoting cholesterol exposure, modulating phospholipid order, and enhancing water penetration across the bilayer. Overall, this study provides mechanistic insights into GO-lipid interactions, suggesting its potential as a novel nanomaterial for controlled modulation of membrane properties, with promising implications in reproductive biology and assisted fertilization technologies.