The spontaneous assembly of a peptide bolaamphiphile in water, namely, RFL₄FR (R, arginine; F, phenylalanine; L, leucine) is investigated, along with its novel properties in surface modification and usage as substrates for cell culture. RFL₄FR self-assembles into nanosheets through lateral association of the peptide backbone. The L₄ sequence is located within the core of the nanosheets, whereas the R moieties are exposed to the water at the surface of the nanosheets. Kinetic assays indicate that the self-assembly is driven by a remarkable two-step process, where a nucleation phase is followed by fast growth of nanosheets with an autocatalysis process. The internal structure of the nanosheets is formed from ultrathin bolaamphiphile monolayers with a crystalline orthorhombic symmetry with cross-β organization. We show that human corneal stromal fibroblast (hCSF) cells can grow on polystyrene films coated with films dried from RFL₄FR solutions. For the first time, this type of amphiphilic peptide is used as a substrate to modulate the wettability of solid surfaces for cell culture applications.

The bola-amphiphilic arginine-capped peptide RFL₄RF self-assembles into nanotubes in aqueous solution. The nanostructure and rheology are probed by in situ simultaneous rheology/small-angle scattering experiments including rheo-SAXS, rheo-SANS, and rheo-GISANS (SAXS: small-angle X-ray scattering, SANS: small-angle neutron scattering, GISANS: grazing incidence small-angle neutron scattering). Nematic alignment of peptide nanotubes under shear is observed at sufficiently high shear rates under steady shear in either Couette or cone-and-plate geometry. The extent of alignment increases with shear rate. A shear plateau is observed in a flow curve measured in the Couette geometry, indicating the presence of shear banding above the shear rate at which significant orientation is observed (0.1–1 s^–1). The orientation under shear is transient and is lost as soon as shear is stopped. GISANS shows that alignment at the surface of a cone-and-plate cell develops at sufficiently high shear rates, very similar to that observed in the bulk using the Couette geometry. A small isotope effect (comparing H₂O/D₂O solvents) is noted in the CD spectra indicating increased interpeptide hydrogen bonding in D₂O, although this does not influence nanotube self-assembly. These results provide new insights into the controlled alignment of peptide nanotubes for future applications.