Bioorthogonal chemistry and illumination controlled programmed size-changeable nanomedicine for synergistic photodynamic and hypoxia-activated therapy

Photodynamic therapy (PDT) can aggravate the hypoxia aggravation and be further utilized for the activation of hypoxia-activated prodrug (HAP). Ideally, photosensitizers (PSs) are mainly administrated to tumor vasculatures adjacent to regions with high oxygen to effectively generate reactive oxygen species (ROS) effectively and further aggravate tumor hypoxia, while the HAP is delivered to the inner tumor as far as possible for efficient activation. However, a delivery system capable of transporting PSs and HAP to the desired region respectively for the optimum effect is urgently needed. Here, we developed a bioorthogonal click chemistry and illumination controlled programmed size-changeable nanomedicine for synergistic photodynamic and hypoxia-activated therapy. It utilized tumor acidity responsive bioorthogonal click reaction for crosslinking nanoparticles to construct a drug depot with tumor vasculatures adjacent region retention for PDT in normoxia. Under laser illumination, cleavage of the ROS-responsive thioketal (TK) crosslinker to release small sized poly(amidoamine) (PAMAM) dendrimer conjugated with HAP for enhanced tumor penetration into the hypoxic region. Therefore, this strategy could differentially deliver PSs and HAP in desired spatial distribution, eventually achieving the enhanced synergistic enhancement in the combined PDT and hypoxia-activated therapy.