Advances in organic fluorescent probes for bromide ions, hypobromous acid and related eosinophil peroxidase-A review

Elemental bromine is among the essential elements for human health. In living organisms, bromide (Br−) and hydrogen peroxide (H2O2) can be catalyzed by eosinophil peroxidase (EPO) to generate a reactive oxygen species (ROS), hypobromous acid (HOBr), which exhibits properties similar to those of hypochlorous acid (HOCl). Moreover, HOBr possesses strong oxidative and antibacterial properties, which are believed to play an important role in the neutrophil host defense system. However, overexpression or misexpression of HOBr can cause organismal and tissue damage, which is closely related to the development of various diseases. Therefore, an increasing number of studies has demonstrated physiological associations with the conversion of Br− to HOBr. With the development of fluorescence imaging technology, developing fluorescent probes with novel structures and high selectivity to detect changes in Br−, HOBr, and the related enzyme EPO levels in organisms has become very important. This paper summarizes Br−, HOBr, and EPO fluorescent probes reported in recent years, including the design principles, mechanisms, optical properties, and bioapplications. Finally, the application prospects and challenges are also discussed.