Aromatic Dipeptide Homologue-Based Hydrogels for Photocontrolled Drug Release

Peptide-based hydrogels are considered of special importance due to their biocompatibility and biodegradability. They have a wide range of applications in the biomedical field, such as drug delivery, tissue engineering, wound healing, cell culture media, and biosensing. Nevertheless, peptide-based hydrogels composed of natural alpha-amino acids are limited for in vivo applications because of the possible degradation by proteolytic enzymes. To circumvent this issue, the incorporation of extra methylene groups within the peptide sequence and the protection of the terminal amino group can increase the enzymatic stability. In this context, we investigated the self-assembly capacity of aromatic dipeptides (Boc-alpha-diphenylalanine and Boc-alpha-dityrosine) and their beta- and gamma-homologues and developed stable hydrogels. Surprisingly, only the Boc-diphenylalanine analogues were able to self-assemble and form hydrogels. A model drug, l-ascorbic acid, and oxidized carbon nanotubes (CNTs) or graphene oxide were then incorporated into the hydrogels. Under near-infrared light irradiation, the photothermal effect of the carbon nanomaterials induced the destabilization of the gel structure, which caused the release of a high amount of drug, thus providing opportunities for photocontrolled on-demand drug release.

Automated summary

Peptide-based hydrogels are widely used in the biomedical field due to their biocompatibility and biodegradability. However, the degradation by proteolytic enzymes limits their in vivo applications. By incorporating extra methylene groups and protecting the terminal amino group, the enzymatic stability of peptide-based hydrogels can be increased. Aromatic dipeptides were found to be able to self-assemble and form stable hydrogels, which were further used for photocontrolled drug release in combination with carbon nanomaterials.