injectable NIR-responsive supramolecular hydrogels encapsulating ROS-triggered chain-breakage prodrug micelles and hydrophilic FeO nanoparticles for enhanced synergistic chemo-photothermal therapy.

Efficient synergistic therapeutic strategies for tumors with high specificity and sensitivity remain a major challenge. An injectable near-infrared (NIR)-responsive supramolecular hydrogel was prepared host-guest interactions between conjugated poly(-phenylglycine)-poly(ethylene glycol) (PNPG-PEG) and α-cyclodextrin. A reactive oxygen species (ROS)-triggered chain-breakage prodrug was composed of a thioketal (TK) linkage of methoxy poly(ethylene glycol) (mPEG) and doxorubicin (DOX). The resulting amphiphilic conjugate mPEG-TK-DOX can self-assemble into prodrug micelles. PEG/poly(etherimide) (PEI)@FeO nanoparticles (PEG/PEI@FeO NPs) were prepared using a thermal decomposition method. The prodrug micelles and PEG/PEI@FeO NPs can be well dispersed into the hydrogel system. In a tumor micro-acid environment, PEG/PEI@FeO NPs catalyze the decomposition of HO to highly toxic ˙OH a Fenton reaction to induce the breakage of ROS-responsive TK bonds for the dissociation of micelles and the continuous release of DOX. PEG/PEI@FeO NPs can also generate an NIR-thermal effect and enhance the photothermal therapy. Notably, by combining with controllable photothermal therapy, the composite hydrogel system shows enhanced synergistic chemo-photothermal therapy for tumors and almost complete and tumor suppression, providing a promising synergistic tumor treatment strategy.