Lipid Membrane Formation on h-BN Modified by Self-Assembled Peptides

Graphene and other two-dimensional (2D) nanomaterials have garnered significant attention as platforms for highly sensitive biosensors due to their exceptional electrical and physical properties [1]. The functionalization of graphene surfaces is pivotal in the development of effective biosensors. Transmembrane proteins perform their native functions within cell membranes, and by mimicking the cell membrane on a graphene surface, we can create innovative graphene biosensors incorporating transmembrane proteins. Indeed, several studies have demonstrated the formation of supported lipid bilayers (SLBs) on graphene at the solid-liquid interface [2]. However, the hydrophobic nature of graphene presents challenges in forming stable SLBs on its surface [3]. Therefore, it is crucial to modify the surface chemistry of graphene without compromising its electronic properties to enable the stable formation of uniform SLBs.
In this study, we developed a method to form stable supported lipid bilayers (SLBs) by modifying the surface of 2D nanomaterials with peptides. Certain peptides are known to self-assemble into monomolecular thick, uniform layers on the surfaces of 2D nanomaterials such as graphene and hexagonal boron nitride (h-BN) [4,5]. They are capable of modifying graphene biosensors as biomolecular scaffold [6-8]. Previous research has shown that peptides with dipeptide repeats of glycine (G) and alanine (A) exhibit ordered self-assembled structures on these 2D materials [9]. We utilized these peptides to enhance the surface modification of 2D materials, aiming to improve SLB formation.
In our experiments, we employed fluorescence microscopy to investigate SLB formation. h-BN, being optically transparent in the visible light range, is well-suited for fluorescence measurements, making it an ideal substrate for our studies. We aimed to determine whether peptide-modified h-BN supports SLB formation. Additionally, we used atomic force microscopy (AFM) to verify peptide self-assembly and SLB formation on h-BN.
To monitor SLB formation, we applied vesicle rupture and fusion methods on h-BN. Fluorescent-tagged lipids were used for fluorescence measurements. During the SLB formation process, the fluorescence intensity of lipids on peptide-modified h-BN significantly increased compared to unmodified h-BN, indicating that peptide surface modification facilitates SLB formation. AFM measurements showed that the height of the SLB on peptide-modified h-BN was approximately 5 nm, consistent with the typical thickness of a lipid bilayer, confirming SLB formation on the substrate.
In the future, it will be possible to design a variety of peptides with the capability to control interactions with SLBs, enabling the formation of cell membrane-like SLBs. These findings illuminate the potential for developing cell membrane-mimicking graphene biosensors using designed peptides.

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