Programmable Release of Chemotherapeutics from Ferrocene‐Based Injectable Hydrogels Slows Melanoma Growth

Abstract Hydrogel‐based injectable drug delivery systems provide temporally and spatially controlled drug release with reduced adverse effects on healthy tissues. Therefore, they represent a promising therapeutic option for unresectable solid tumor entities. In this study, a peptide‐starPEG/hyaluronic acid‐based physical hydrogel is modified with ferrocene to provide a programmable drug release orchestrated by matrix‐drug interaction and local reactive oxygen species (ROS). The injectable ROS‐responsive hydrogel (hiROSponse) exhibits adequate biocompatibility and biodegradability, which are important for clinical applications. HiROSponse is loaded with the two cytostatic drugs (hiROSponse dox/ptx ) doxorubicin (dox) and paclitaxel (ptx). Dox is a hydrophilic compound and its release is mainly controlled by Fickian diffusion, while the hydrophobic interactions between ptx and ferrocene can control its release and thus be regulated by the oxidation of ferrocene to the more hydrophilic state of ferrocenium. In a syngeneic malignant melanoma‐bearing mouse model, hiROSponse dox/ptx slows tumor growth without causing adverse side effects and doubles the relative survival probability. Programmable release is further demonstrated in a tumor model with a low physiological ROS level, where dox release, low dose local irradiation, and the resulting ROS‐triggered ptx release lead to tumor growth inhibition and increased survival.