Highly-controllable drug release from core cross-linked singlet oxygen-responsive nanoparticles for cancer therapy.

Highly-controllable release consisting of preventing unnecessary drug leakage at physiologically normal tissues and triggering sufficient drug release at tumor sites is the main aim of nanoparticle-based tumor therapy. Developing drug-conjugation strategies with covalent bonds in response to a characteristic stimulus, such as reactive oxygen species (ROS) generated by photodynamic therapy (PDT) has attracted much attention. ROS can not only cause cytotoxicity, but also trigger the cleavage of ROS-responsive linkers.