Histidine-based hydrogels via singlet-oxygen photooxidation

Histidine Photooxygenation Chemistry: Mechanistic Evidence and Elucidation

Histidine photooxygenation has been the subject of extensive investigation for many years. The intricate nature of histidine distinguishes it from other amino acids, as its side chain readily undergoes changes in charge state and tautomerization in response to pH, and the polarity of the imidazole ring inverts upon oxidation. This complexity gives rise to a diverse range of oxidation products and mechanisms, posing challenges in their interpretation. This review aims to provide a thorough overview of the chemistry involved in histidine photooxygenation, encompassing a comprehensive analysis of resulting products, mechanisms engaged in their formation, and analytical techniques that have contributed to their identification. Additionally, it explores a wide range of applications stemming from this transformation, offering valuable insights into its practical implications in fields such as materials science, biomedical research, and drug development. By bridging the existing gap in literature, this review serves as a resource for understanding the intricacies of histidine photooxygenation and its diverse ramifications.

Peptide- and Metabolite-Based Hydrogels: Minimalistic Approach for the Identification and Characterization of Gelating Building Blocks

Minimalistic peptide- and metabolite-based supramolecular hydrogels have great potential relative to traditional polymeric hydrogels in various biomedical and technological applications. Advantages such as remarkable biodegradability, high water content, favorable mechanical properties, biocompatibility, self-healing, synthetic feasibility, low cost, easy design, biological function, remarkable injectability, and multi-responsiveness to external stimuli make supramolecular hydrogels promising candidates for drug delivery, tissue engineering, tissue regeneration, and wound healing. Non-covalent interactions such as hydrogen bonding, hydrophobic interactions, electrostatic interactions, and π-π stacking interactions play key roles in the formation of peptide- and metabolite-containing low-molecular-weight hydrogels. Peptide- and metabolite-based hydrogels display shear-thinning and immediate recovery behavior due to the involvement of weak non-covalent interactions, making them supreme models for the delivery of drug molecules. In the areas of regenerative medicine, tissue engineering, pre-clinical evaluation, and numerous other biomedical applications, peptide- and metabolite-based hydrogelators with rationally designed architectures have intriguing uses. In this review, we summarize the recent advancements in the field of peptide- and metabolite-based hydrogels, including their modifications using a minimalistic building-blocks approach for various applications.