Cross-linker engineering of hydrogel enables photothermal therapy and controlled drug release

Herein we disclose an approach that provides access to multifunctional polymeric hydrogels by cross-linker engineering. To this purpose, a new squaraine dye, Sq1, was synthesized. It was found that Sq1 could generate hyperthermia upon irradiation with NIR (808 nm) light. More importantly, PAAm hydrogels incorporating Sq1 as a covalent cross-linker (Sq1@PAAm) can be obtained successfully. Delightfully, cross-linker-engineered PAAm hydrogels can be used as an efficient photosensitizer for photothermal therapy. In vitro studies with human melanoma cell line (SK-MEL-30/An1) cell lines show that Sq1@PAAm hydrogels can eliminate more than 70% of cancer cells. Finally, methotrexate (MTX) as a model drug is loaded into the hydrogel, and release behavior is evaluated. Notably, sustained MTX release was possible by irradiating the Sq1@PAAm hydrogel. Overall, we have successfully shown that the cross-linker engineering of hydrogel enables photothermal therapy. Furthermore, drugs could be loaded into the porous hydrogel network, and on-demand release could be successfully achieved using the Sq1@PAAm core.