Targeting tumor hypoxia with stimulus-responsive nanocarriers in overcoming drug resistance and monitoring anticancer efficacy

Although existing nanomedicines have focused on the tumor microenvironment with the goal of improving the effectiveness of conventional chemotherapy, the penetration of a tumor’s core still represents a formidable barrier for existing drug delivery systems. Therefore, a novel multifunctional hypoxia-induced size-shrinkable nanoparticle has been designed to increase the penetration of drugs, nucleic acids, or probes into tumors. This cooperative strategy relies on three aspects: (i) the responsiveness of nanoparticles to hypoxia, which shrink when triggered by low oxygen concentrations; (ii) the core of a nanoparticle involves an internal cavity and strong positive charges on the surface to deliver both doxorubicin and siRNA; and (iii) a reactive oxygen species (ROS) probe is incorporated in the nanoparticle to monitor its preliminary therapeutic response in real time, which is expected to realize the enhanced efficacy together with the ability to self-monitor the anticancer activity. A more effective inhibition of tumor growth was observed in tumor-bearing zebrafish, demonstrating the feasibility of this cooperative strategy for in vivo applications. This research highlights a promising value in delivering drugs, nucleic acids, or probes to a tumor’s core for cancer imaging and treatment.