Interaction and assembly of graphene oxide nano-flakes in lipid membranes

Graphene-based nano-technology is the future of biomedical devices. As cellular membrane is the first target of any foreign molecule to interact with living organism, here, the membrane is mimicked by stack of lipid bilayers and its structures have been probed by x-ray reflectivity and grazing incidence diffraction techniques. Lipid-GO complex has exhibited two sets of lamellar diffraction peaks illustrating a GO-rich micro-domain present in the matrix of phospholipid bilayers (GO-poor phase). In GO-rich phase, the flakes are observed to penetrate into the hydrophobic core of the membrane altering the bilayer thickness and electron density while in GO-poor phase they are destined to remain in hydrophilic head group region [1]. To understand the role of electrostatics, a single layer of lipids formed at air-water interface with varying charge entity has been. The surface pressure-area isotherm shows an interaction of GO with positively charged lipid while it shows a weak interaction with the zwitterionic one. The interaction with a negatively charged lipid was almost negligible. X-ray data show that the flakes bring a discerning effect in the out-of-plane ordering of the positively charged lipid layer, whereas it does not alter the in-plane structure.