Stabilisation of lipid membranes by β-peptide fibres

Hydrogels are three-dimensional networks of nanofibres that have the ability to retain biological fluids and are currently being investigated in a variety of biomedical applications. The ability to tune their physical and chemical properties makes peptide-hydrogels ideal candidates for mimicking the extracellular matrix or supporting soft-tissues in an in vivo setting. However, the physical interactions between the peripheries of the hydrogels and the cellular membranes, which are crucial for their successful integration within the biological environment, have not been extensively studied. We have recently developed β-peptides as a new class of self-assembled peptide-based hydrogels for use in a variety of in vitro and in vivo applications. The aim of this study was to use β-peptide fibres as a substrate to form a supported lipid bilayer (SLB) system in order to assess the impact of the β-peptide 2-D scaffold on the topography and nanomechanical properties of the lipid membrane using atomic force microscopy (AFM). Mica-SLBs were first used as model phospholipid membranes to image the topography of the lipid bilayer with AFM. Four N-acetyl-lipidated β-peptide monomers were then self-assembled in solution, dried on a mica surface and the liposomes deposited, to cushion the SLBs. High resolution AFM imaging of the β-peptide fibres revealed the formation of two distinct populations: a fibre underlayer that fully covered the entire mica surface and large fibres on top of the underlayer. The interactions of the β-peptide fibres with SLBs were further analysed by quantifying the nanomechanical properties of the SLBs and showed increased stability of the POPC/POPE/POPS (6:3:1) lipid bilayer domains. The results indicate that the presence of RGD motifs within the β-peptide fibres enhanced the stability of bilayer domains by electrostatic interactions with the phosphate groups within the SLBs.