Domain Localization by Graphene Oxide in Supported Lipid Bilayers

Area of Science:

• Materials Science
• Surface Chemistry
• Biophysics

Background:

• Supported lipid bilayers (SLBs) mimic cell membranes and are crucial for studying lipid-protein interactions.
• Graphene oxide (GO) is a novel material with unique surface properties, including amphiphilicity.
• Understanding lipid domain formation and localization on surfaces is key to designing advanced biomaterials.

Purpose of the Study:

• To investigate the localization mechanism of gel-phase lipid domains on graphene oxide (GO) within supported lipid bilayers (SLBs).
• To elucidate the role of GO's amphiphilic properties in directing lipid domain formation and distribution.
• To explore the phase behavior of lipid bilayers containing cholesterol on GO surfaces.

Main Methods:

• Fabrication of binary and ternary supported lipid bilayers (SLBs) on SiO2/Si substrates functionalized with graphene oxide (GO) flakes.
• Utilizing fluorescence microscopy and atomic force microscopy (AFM) to visualize and analyze lipid domain distribution and morphology.
• Controlled cooling rates were employed to study the effect on gel-phase domain condensation.

Main Results:

• Gel-phase domains (composed of DPPC) preferentially localized on GO flakes, while the liquid crystalline (Lα) phase enriched the bare SiO2 surface.
• Lower cooling rates enhanced the condensation of gel-phase domains on GO.
• In ternary bilayers, liquid ordered (Lo) phase domains also segregated onto GO, leaving fluid components in the surrounding regions.

Conclusions:

• Graphene oxide's amphiphilic surface properties drive the preferential nucleation and condensation of rigid lipid domains (gel and Lo phases) during SLB formation.
• This selective localization mechanism on GO influences the overall phase distribution within the supported lipid bilayer.
• GO serves as a platform for controlling lipid organization, with potential applications in biosensing and membrane biophysics.