Selective tuning of side chain polarity in an aromatic peptide results supramolecular nanofibrils having amyloidogenic property. These nanofibrils also can arrest solvent molecules leading to sol-to-gel phase transition. Interestingly, the hydrogel material is mechanically robust and thixotropic in nature.

Triggering higher order assembly, peptides form a number of nanoscale architectures. Self-assembly of phenylalanine homopeptides and its derivatives have been studied extensively, but the supramolecular assembly of aromatic peptides in interplay with side chain polarity is yet to be understood. Herein, the p-nitrophenylalanine, H-Phe(p-NO₂)-OH, a chemically modified aromatic amino acid, has been shuffled in a highly aromatic peptide, Boc-Phe-Phe-Phe-OH (P1), which results three mutated analogs having different polarity. The morphological investigation reveals that except Boc-Phe(p-NO₂)-Phe-Phe-OH (P2), all peptides aggregate into supramolecular nanofibrils in aqueous solution. The long entangled nanofibrils formed by Boc-Phe-Phe(p-NO₂)-Phe-OH (P3) are able to arrest the solvent molecules leading to “sol-to-gel” phase transition. Interestingly, the hydrogel is mechanically robust and the gel fibrils are amyloidogenic in nature. Conformational analysis reveals the presence of cross-β arrangement of the β-strand in the gel fibrils. The rheological studies explore the thixotropic property of the self-supported hydrogel matrix. The studies establish that the supramolecular interactions can be tuned modulating the side-chain polarity of the amino acid residues. Overall, it paves a new paradigm to fabricate peptide-based biomaterials for imminent applications.