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In the context of prodrug nanomedicines for cancer therapy, one of the great challenges is the slow and variable release of the parent drug in tumors. Recently, many smart redox-sensitive nanocarriers have been developed to address this problem. However, due to significant tumor heterogeneity, some redox-sensitive nanomedicines still show poor selectivity in drug release. Herein, we report the design and synthesis of a ROS-triggered prodrug nanoplatform fabricated with oxidation-responsive cabazitaxel (CTX) prodrugs for synergistic chemo-photodynamic therapy, thioether-/selenoether-linked conjugates of CTX and oleic acid (OA). These prodrugs can be readily self-assembled into nanoparticles, with pyropheophorbide a (PPa) co-encapsulated into the prodrug-nanosystem for combination therapy. The dual-source ROS-responsive prodrug nanosystems selectively and rapidly release CTX not only in response to endogenous ROS overproduced in tumor cells, but also to exogenous PPa-generated ROS under laser irradiation. Moreover, the selenium-containing linkage demonstrates significant advantages over a sulfur-containing linkage in terms of ROS-triggered drug release and cytotoxicity. The prepared prodrug-nanosystems significantly prolong the systemic circulation and tumor distribution of both CTX and PPa, thereby demonstrating synergistic chemo-photodynamic therapy in vivo. All these drug delivery advantages render the nanosystem extremely promising for cancer treatment.

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Hyaluronic acid (HA) is a natural ligand of tumor-targeted drug delivery systems (DDS) due to the relevant CD44 receptor overexpressed on tumor cell membranes. However, other HA receptors (HARE and LYVE-1) are also overexpressing in the reticuloendothelial system (RES). Therefore, polyethylene glycol (PEG) modification of HA-based DDS is necessary to reduce RES capture. Unfortunately, pegylation remarkably inhibits tumor cellular uptake and endosomal escapement, significantly compromising the in vivo antitumor efficacy. Herein, we developed a Dox-loaded HA-based transformable supramolecular nanoplatform (Dox/HCVBP) to overcome this dilemma. Dox/HCVBP contains a tumor extracellular acidity-sensitive detachable PEG shell achieved by a benzoic imine linkage. The in vitro and in vivo investigations further demonstrated that Dox/HCVBP could be in a "stealth" state at blood stream for a long circulation time due to the buried HA ligands and the minimized nonspecific interaction by PEG shell. However, it could transform into a "recognition" state under the tumor acidic microenvironment for efficient tumor cellular uptake due to the direct exposure of active targeting ligand HA following PEG shell detachment. Such a transformative concept provides a promising strategy to resolve the dilemma of natural ligand-based DDS with conflicting two processes of tumor cellular uptake and in vivo nonspecific biodistribution.