Structural Fine-Tuning and Gel-Forming Properties of Peptides Containing Aromatic Amino Acid Residues

Background Peptides are versatile building blocks for nanomaterials. Their self-assembled hydrogels feature tunable properties and good biocompatibility, enabling applications in cell culture, tissue engineering, and drug delivery. Peptide self-assembly arises from the synergy of multiple noncovalent interactions; among them, π–π stacking between aromatic residues is widely considered to be associated with ordered assembly in aromatic peptides. Methods Eight aromatic heptapeptides containing a “-Y-F-F-” motif were designed to examine how subtle variations in side-chain hydrophobicity correlate with self-assembly and gelation behaviors commonly attributed to aromatic stacking. Results Fluorescence and FT-IR results indicated that replacing Gly with the slightly bulkier and more hydrophobic Ala between two Phe residues is associated with more ordered networks, and only AA, GA, Fmoc-AA, and Fmoc-GA formed hydrogels under the tested conditions. And TEM/AFM and rheological measurements further revealed qualitative differences in nanofiber morphologies and sequence-dependent self-healing behavior among these gels. As a proof of concept, AA and GA gels exhibited low cytotoxicity, and their DOX-loaded gels displayed pH-responsive release. Notably, A-DOX showed a 66.91% higher cumulative release at pH 6.0 than at pH 7.4, leading to more sustained inhibition of HeLa cell proliferation compared with free DOX. Conclusion These results revealed that aromatic stacking together with an appropriate degree of hydrophobicity favors ordered peptide assembly, and that modest sequence changes can translate into distinct gel structures and drug-release functions.