Luminescent ultrashort peptide hydrogelator with enhanced photophysical implications and biocompatibility†

Abstract

Luminescent peptide hydrogelators have garnered significant attention in biomedical sciences and materials chemistry due to their biological relevance and tunable photophysical features. In this work, we have designed and synthesized a novel ultrashort peptide hydrogelator comprising a tripeptide sequence (FFE) integrated with 1,8-naphthalimide (NI) as an aggregation-induced emissive unit having rich and tuneable photophysical properties. The hydrogelator could self-assemble and form a self-supporting hydrogel having a highly ordered intertwined network structure at pH 5.5 with a minimum gelation concentration of 1 wt/v%. Interestingly, due to the presence of the emissive unit, the assembly could demonstrate strong blue luminescence, which has been thoroughly investigated experimentally. Moreover, spectroscopic investigations and molecular dynamics simulation studies suggest the formation of a β-sheet structure through extended intermolecular H-bonding interactions within the peptide backbones and the strong π–π-stacking interaction among aromatic units, which drive the self-assembly and hydrogelation. The emissive unit of the peptide could arrange in a J-type aggregation pattern and adopt right-handed helical induced chirality in the assembled state. Additionally, the system could exhibit a high safety profile and excellent biocompatibility, when tested in a series of cell lines in vitro. Finally, the intracellular uptake of the system has been exploited, showcasing its luminescence characteristics for potential applications in cellular imaging. The luminescent system holds significant promise for advancing cellular imaging techniques, offering new avenues for research in the future. Briefly, this work highlights the importance of luminescent ultrashort peptide hydrogelators for developing next-generation low-cost functional biomaterials.