Ultra-sensitive responsive near-infrared fluorescent nitroreductase probe with strong specificity for imaging tumor and detecting the invasiveness of tumor cells.

Hypoxia plays an important role in cancer progression, which is a characteristic feature of the tumor micro-environment and reflects the invasiveness of tumor cells. Nitroreductase (NTR) is overexpressed in hypoxic tumors, which making it an efficient target for detecting the hypoxic state in tumor. In this work, a new type of nitro-based fluorescent probe, named HNT-NTR, has been proposed, HNT-NTR could detect specifically and rapidly the NTR degree, which reflects the level of hypoxia in bidimensional (2D) tumor cells, three-dimensional (3D) tumor spheres and even the real tumors in vivo without biological toxicity. Most importantly, according to the research, HNT-NTR even could distinguish tumor cells from other normal cells in vivo and reflect the invasiveness of tumor cells by the near-infrared fluorescence intensity, which provides a new way of clinical pathologic diagnosis. All in all, HNT-NTR not only is proven to be an ideal probe for detecting solid tumors in vivo, but also has great potential to distinguish if cells are benign or malignant and even guide therapeutic applications in the clinic.