A common strategy used to functionalize the surface of a biomaterial is to coat it with proteins or peptides. Our group has used GRGDSP 'peptide amphiphiles' - peptides conjugated to lipid-like tails - to create biomimetic assemblies, i.e. supported bilayers, that are capable of inducing fibroblast adhesion and proliferation. A special feature of the supported bilayer is that it allows control of the density and spatial organization of the ligand in a biologically relevant fashion. In this contribution we highlight the specifics of the vesicle fusion method used to create smooth supported bilayers as determined by fluorescence microscopy, FRAP and QCM. We describe the effect of changing the ligand density and accessibility (in terms of the distance of the RGD group from the surface) on cell adhesion. Further, we explore the structure of mixed supported bilayers incorporating RGD ligands using AFM to probe for the formation of locally phase-separated domains enriched in RGD that can enhance cell adhesion and focal contact formation.