Fluorescent probes for the detection of alkaline phosphatase in biological systems: Recent advances and future prospects

Alkaline phosphatase (ALP), an important enzyme in living organisms, plays significant roles in the hydrolysis of phosphate groups from nucleic acids, proteins, and other substrates. Abnormal level of ALP in serum is related to a variety of diseases. Low expression of ALP can cause blood diseases, such as anemia and leukemia, while over-expression of ALP can lead to disorders in liver, prostate, endocrine system, and bone tissues. Therefore, to monitor the ALP level in physiological and pathological events, it is in urgent need to develop a rapid, accurate, sensitive, and non-invasive approach, which can also be of great significance for the improvement of corresponding clinical agents. With the development of fluorescent probes, many advantages of fluorescent probes for ALP detection, such as simple operation, non-invasive, real-time imaging, economy, fast response, and so on, have been gradually highlighted. In this review, we enumerated almost all the ALP fluorescent probes from 2009 to now and summarized their respective characteristics, in order to provide a unified platform for their standardized evaluation. Meanwhile, we tried to systematically review the research progress of ALP fluorescent probes, including both small-molecule and nanoscale ones. Logically, we focused on the structures, reaction mechanisms, and biological applications of ALP fluorescent probes. In addition, the prospects of ALP in the near future have also been foreseen. We hope that this review will be helpful for the investigators who are interested in ALP-associated biological procedures, and even in the regulation of more extensive enzyme levels.