Near-infrared light-responsive alginate hydrogels based on diselenide-containing cross-linkage for on demand degradation and drug release.

A biodegradable, near-infrared (NIR) - responsive hydrogel is one of the most promising strategies as a remotely triggered drug carrier. In this study, novel NIR-responsive hydrogels based on alginate structures were prepared for controllable drug release. The hydrogels were formed rapidly by reacting norbornene-functionalized alginates and tetrazine cross-linkers containing diselenide bonds via inverse electron demand Diels-Alder click chemistry. In order to manipulate their properties, we prepared hydrogels with various cross-linking densities. NIR sensitive indocyanine green (ICG) and a drug, doxorubicin (DOX) were incorporated in the hydrogel matrix during gelation. The hydrogels showed a suppressed release profile under physiological conditions, while NIR light triggered a rapid release of DOX. Under NIR-light irradiation, ICG generated reactive oxygen species which could decompose diselenide bonds in the hydrogel matrix, inducing the gel-sol transition and release of entrapped DOX. The degradation of hydrogels could be also controlled by the ratio of the precursors.