Recent research progress of red-emitting/near-infrared fluorescent probes for biothiols

Small-molecule biological thiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), occupy a vital position in physiological and pathological activities. Abnormal fluctuations of their concentrations are often closely connected with a variety of diseases. Rapid and accurate detection of these biothiols is of great importance. Due to the advantages such as low background interference, strong tissue penetration and less damage to biological samples, studies on red-emitting/near-infrared fluorescent probes have attracted great interest from researchers. Many red-emitting/near-infrared fluorescent probes for biothiols have been reported. However, there are few reviews about these probes. Here, we focus on the biothiol fluorescent probes with excellent performance and red emission/near-infrared emission signals reported in the past five years (2017-2021). They are classified according to the types of fluorophores constituting the probe molecules, including dicyanoisophorone, tricyanofuran, rhodamine, dipyrrole fluoroboron (BODIPY), cyanine and other fluorophores. The properties of the fluorophores mentioned above are introduced at first. Then the red/near-infrared biothiol fluorescent probes harboring these fluorophores are described in detail from the molecular designs, fluorescence properties, recognition mechanisms, and biological applications. Finally, the problems and development prospects of red/near-infrared biothiol fluorescent probes are discussed. We believe that this brief review can provide a reference for beginners to quickly understand this field and some help for researchers who design novel near-infrared biothiol fluorescent probes.

Automated summary

This article reviews the recent advances in red-emitting/near-infrared fluorescent probes for small-molecule biological thiols. The probes are classified based on the types of fluorophores used, and their molecular designs, fluorescence properties, recognition mechanisms, and biological applications are discussed in detail. The challenges and future prospects of red/near-infrared biothiol fluorescent probes are also addressed.