Cellular Uptake and Antioxidant Activity of H₂S-Releasing Tetrapeptide Supramolecular Polymer Nanostructures

Self-assembled peptide–H₂S donor conjugates (PHDCs) can deliver hydrogen sulfide in vitro and in vivo, yet the link between the supramolecular nanostructure morphology and cellular uptake remains unclear. Herein, we designed constitutionally isomeric PHDCs that self-assembled in aqueous solution into either nanoribbons, nanofibers, or nanobelts with various dimensions based on cryogenic transmission electron microscopy and small-angle X-ray scattering. Nile-red loaded PHDCs showed morphology-dependent uptake by H9C2 cells based on fluorescence microscopy combined with flow cytometry and confocal imaging, where narrow, helically twisted nanoribbons entered most efficiently. All PHDCs released H₂S at similar rates, but the amount of H₂S released inside the cells depended on the internalization ability of each PHDC. Consistent with these results, the narrow twisted nanoribbons afforded the greatest protection against H₂O₂-induced oxidative stress. Overall, this study highlights how subtle molecular-level changes can influence nanostructure formation in supramolecular assemblies and ultimately affect their cellular uptake and biological activities.