New RGD-peptide amphiphile mixtures containing a negatively charged diluent

Here, we studied the self-assembly of two peptide amphiphiles, C₁₆-Gly-Gly-Gly-Arg-Gly-Asp (PA 1: C₁₆-GGG-RGD) and C₁₆-Gly-Gly-Gly-Arg-Gly-Asp-Ser (PA 2: C₁₆-GGG-RGDS). We showed that PA 1 and PA 2 self-assemble into nanotapes with an internal bilayer structure. C₁₆ chains were highly interdigitated within the nanotape cores, while the peptide blocks formed water-exposed β-sheets too. PA 1 nanotapes were characterized by one spacing distribution, corresponding to a more regular internal structure than that of PA 2 nanotapes, which presented two different spacing distributions. We showed that it is possible to obtain homogeneous nanotapes in water by co-assembling PA 1 or PA 2 with the negatively charged diluent C₁₆-Glu-Thr-Thr-Glu-Ser (PA 3: C₁₆-ETTES). The homogeneous tapes formed by PA 1–PA 3 or PA 2–PA 3 mixtures presented a structure similar to that observed for the corresponding pure PA 1 or PA 2 nanotapes. The mixed nanotapes, which were able to form a stabilized matrix containing homogeneously distributed cell adhesive RGD groups, represent promising materials for designing new cell adhesion substrates.