Recent progress in the design principles, sensing mechanisms, and applications of small-molecule probes for nitroreductases

As one of the most representative hypoxic enzymes, nitroreductases (NTRs) play momentous roles in malignant tumor progression, metastasis, invasion and angiogenesis. They are also a key hallmark of highly aggressive disease in various hypoxic tumor cells. In addition, NTRs participate in essential processes of detoxification, pro-drug activation as well as radiation therapy. Thus, the detection of NTRs has great importance for theranostic and drug development. In this review, we focused on the design principles, sensing mechanisms and biological applications of small-molecule probes for NTRs detection over the past ten years (2010–2020). We also highlighted the challenges and future directions in this rapidly developing field. Significantly, we hope that some insights and inspiration for future research work will be provided to surmount the Achilles’ Heels of the small-molecule probes, such as limited application, for detecting NTRs.