Injectable photosensitizing supramolecular hydrogels: A robust physically cross-linked system based on polyvinyl alcohol/chitosan/tannic acid with self-healing and antioxidant properties

The development of injectable and photosensitizing supramolecular hydrogels has proved to be a challenging and interesting task. In this study, N, N' -di-(L-alanine)-3,4,9,10-perylene tetracarboxylic diimide (PDI-Ala), as a photosensitizing agent, was incorporated into single (PVA-CS-PDI/TA) and double cross-linked (PVA-CS-PDI/ TA/Fe (III)) hydrogels formed by poly (vinyl alcohol) (PVA), chitosan (CS), and tannic acid (TA) through a freeze-thawing method based on non-covalent interaction (hydrogen bonding and metal coordination). TA molecules act as cross-linkers to connect polymer chains through multiple hydrogen bonds and cross-link them using coordinate bonds in the presence of Fe (III) ions. The double cross-linked hydrogels had a higher singlet oxygen quantum yield than single cross-linked hydrogels under 660 nm laser irradiation, indicating those that could be more efficient in photodynamic therapy (PDT). Supramolecular hydrogels with interconnected porous morphologies exhibited mechanical strength, injectability, self-healing and shear-thinning capabilities, antioxi-dant and antibacterial properties. Additionally, the supramolecular photosensitizing hydrogels showed excellent biocompatibility without showing evident cytotoxicity and hemolysis in vitro. This study presents a straight-forward and cost-effective approach to prepare multifunctional physical cross-linking supramolecular hydrogels, appropriate for large-scale preparation, which shows great potential in biomedical applications such as PDT and wound dressings.

Automated summary

This study developed injectable and photosensitizing supramolecular hydrogels with interconnected porous morphology. The hydrogels exhibited mechanical strength, injectability, self-healing and shear-thinning capabilities, as well as antioxidant and antibacterial properties. They also showed excellent biocompatibility and potential for biomedical applications.