Tracking Cancer Metastasis In Vivo by Using an Iridium-Based Hypoxia-Activated Optical Oxygen Nanosensor.

We have developed a nanosensor for tracking cancer metastasis by noninvasive real-time whole-body optical imaging. The nanosensor is prepared by the formation of co-micelles from a poly(N-vinylpyrrolidone)-conjugated iridium(III) complex (Ir-PVP) and poly(ε-caprolactone)-b-poly(N-vinylpyrrolidone) (PCL-PVP). The near-infrared phosphorescence emission of the nanosensor could be selectively activated in the hypoxic microenvironment induced by cancer cells. The detection ability of the nanosensor was examined in cells and different animal models. After intravenous injection, the nanosensor can be effectively delivered to the lung and lymph node, and cancer cell metastasis through bloodstream or lymphatics can be quickly detected with high signal-to-background ratio by whole-body imaging and organ imaging. Moreover, the nanosensor exhibits good biocompatibility both in vitro and in vivo. The nanosensor is believed to be a powerful tool for the diagnosis of cancer metastasis.