Design of light/ROS cascade-responsive tumor-recognizing nanotheranostics for spatiotemporally controlled drug release in locoregional photo-chemotherapy

Carrier-free nanotheranostics with high drug loading and no carrier-related toxicity are highly promising cancer therapy agents. However, the limited tumor accumulation and poorly controlled drug release of these nanotheranostics continue to be major challenges that restrict clinical applications. In this study, we develop a tumor-recognizing carrier-free nanotheranostic with light/reactive oxygen species (ROS) cascade-responsiveness for spatiotemporally selective photo-chemotherapy. The nanotheranostic is constructed by co-assembly of the indocyanine green (ICG) photosensitizer and the mannose-thioketal-doxorubicin conjugate (MAN-TK-DOX) (abbreviated as IMTD), efficiently preventing premature DOX leakage during blood circulation while reducing nonspecific damage to normal tissues/cells. Once accumulated in tumor tissues, IMTD rapidly diffuses into cancer cells via lectin receptors-mediated endocytosis. Photoacoustic/fluorescence-imaging-guided laser irradiation induces local hyperthermia and ROS generation in tumor cells, thereby promoting apoptosis. Together, the ICG-generated ROS and the endogenous ROS in cancer cells synergistically enhance DOX release, resulting in more efficient chemotherapeutic effects. The in vitro and in vivo results consistently demonstrate that IMTD achieves superior tumor accumulation, highly controllable drug release, and synergetic photo-chemotherapy. Therefore, the co-assembly of an ROS-sensitive targeting ligand-chemodrug conjugate and a photosensitizer could be used to develop spatiotemporally light-activatable nanotheranostics for precision cancer therapy. Synergistic phototherapy and chemotherapy have been considered as a promising cancer treatment modality to maximize the therapeutic efficacy. Unfortunately, most nanodrugs consisting of chemotherapeutic drug and photosensitizer suffer from suboptimal tumor accumulation and poorly controlled drug release, which results in reduced therapeutic outcome. In this study, Mannose (MAN) was conjugated to the anticancer drug doxorubicin (DOX) by a ROS-sensitive thioketal linker (TK), the obtained amphiphilic MAN-TK-DOX could serve as an ideal self-carrier material to deliver photosensitizer, thus to achieve high-efficient tumor-targeting, spatiotemporal controlled drug release, and superior antitumor effect. We believe that the ROS-sensitive amphiphilic targeting ligand-chemodrug conjugate could be developed as a universal approach for designing tumor-targeted nanodrugs with precisely controlled drug release.