Ir(III) complexes have attracted much attentions in bio-imaging and targeted therapies due to their outstanding advantages such as large Stokes shift, short incubation time, long luminescence lifetime, enhanced photo-stability and simple color tuning method. Furthermore, Ir(III) complexes showed remarkable efficiency of reactive oxygen species (ROS) generation as photosensitizers via electron (type I) and energy transfer (type II). Despite these great characteristics, the use of Ir(III) complexes as therapeutic agents has been limited because of their poor biocompatibility and water solubility.
 Herein, we provide reduction-triggered self-cross-linked nanogel which is compatible with iridium complexes and hydrophilic. We synthesized iridium complexes(TIr3) encapsulated in self-cross-linked hyperbranched polyglycerol nanogels(Naph-P(G-co-SSG) nanogels) by using the thiol-disulfide intermolecular exchanges. This Ir(III) complex involved nanogel was much soluble in physiological environments compared to the Ir(III) complex. Through DLS and TEM, the size of nanogels were confirmed and release profile of iridium complex in physiological environment were detected by UV-vis absorption. With these formed nanoparticles, we expect enhancement of cell viability and photo-toxicity index for cancer cells due to better biocompatibility and enhanced permeability and retention (EPR) effect of nanoparticles.