Reduced graphene oxide directed self-assembly of phospholipid monolayers in liquid and gel phases

Abstract

The response of cell membranes to the local physical environment significantly determines many biological processes and the practical applications of biomaterials. A better understanding of the dynamic assembly and environmental response of lipid membranes can help understand these processes and design novel nanomaterials for biomedical applications. The present work demonstrates the directed assembly of lipid monolayers, in both liquid and gel phases, on the surface of a monolayered reduced graphene oxide (rGO). The results from atomic force microscopy indicate that the hydrophobic aromatic plane and the defect holes due to reduction of GO sheets, along with the phase state and planar surface pressure of lipids, corporately determine the morphology and lateral structure of the assembled lipid monolayers. The DOPC molecules, in liquid phase, probably spread over the rGO surface with their tails associating closely with the hydrophobic aromatic plane, and accumulate to form circles of high area surrounding the defect holes on rGO sheets. However, the DPPC molecules, in gel phase, prefer to form a layer of continuous membrane covering the whole rGO sheet including defect holes. The strong association between rGO sheets and lipid tails further influences the melting behavior of lipids. This work reveals a dramatic effect of the local structure and surface property of rGO sheets on the substrate-directed assembly and subsequent phase behavior of the supported lipid membranes.

Dispersal of pristine graphene for biological studies

“…This suggests that the neutral lipids associated with pristine graphene and avoided aggregation in saline for longer than for rGO dispersions. 39,40 G/lipid was indicated as few-layer graphene by AFM (Table 1 and Fig. 2) and by the typical shape of the Raman 2D band (Fig.…”

“…However, neutral liposomes failed to stabilize aqueous rGO, and removal of excess positively-charged liposomes caused rGO agglomeration. 39,40 Pristine FLG has been directly exfoliated from graphite in the neutral lipid phosphatidylcholine (PC) in chloroform by formation of reverse micelles on the graphene surface. 41 FLG is also reported to be exfoliated into liposomes with stable location between the hydrocarbon chains of the phospholipid bilayer.…”

“…Liposomes have been widely used to coat lipid layers onto graphene lms, which show a variety of morphologies and structures. 39,40 From AFM and modelling studies, the lipid aliphatic chains interact with the aromatic regions of graphene in ordered parallel arrangements, which were relatively sparsely arranged compared to densely-packed liposome membranes. 40 Similar arrangements have been suggested for the destructive extraction of lipids from bacterial membranes by graphene sheets.…”

Strong hydrophobic interaction between graphene oxide and supported lipid bilayers revealed by AFM

“…Graphene‐related nanomaterials are believed to have great potential in applications in the fields of biology and biomedicine (Liu et al, , ; Sanchez et al, ; Sun et al, ; Wang et al, ; Yi and Gao, ), and have been used for biosensors (Ali et al, ; Ang et al, ; Liu et al, ; Qing et al, ), antibacterials (Dallavalle et al, ; Duan et al, ; Li et al, ; Mao et al, ; Pham et al, ; Pykal et al, ; Tu et al, ), bioimaging (Qian et al, ; Shi et al, ; Sun et al, ; Wang et al, ), regulation of cell growth and differentiation (Lee et al, ; Ruiz et al, ). Recently, the interaction between graphene oxide (GO) and cell membranes, including supported lipid bilayers (SLBs), has become the focus of many researchers (Frost et al, ; Furukawa and Hibino, ; Lei et al, ; Li et al, a,b; Okamoto et al, ; Phan et al, ; Rui et al, ; Wu et al, ) not only because cell membrane is the first barrier when GO interacts with intracellular components, but also it can provide us valuable information on physicochemical nature of GO. In terms of the structure, GO is a highly oxidized form of graphene, which retains the hydrophobic sp2‐hybridized domains, as well as the hydrophilic sp3‐hybridized groups including C–OH, C–O–C, and –COOH (Andre Mkhoyan et al, ; Boukhvalov and Katsnelson, ; Dreyer et al, ; Erickson et al, ).…”

Adsorption and binding dynamics of graphene-supported phospholipid membranes using the QCM-D technique

“…In contrast, the binding event supported on a bare Au chip ( Figure 5(b)) shows a frequency a value of -153. 30 Hz at the end of the stabilization region (steps B-C) after the adsorption of intact vesicles (step A). Then, the frequency reaches a value of -217.…”