Recent advances in fluorescent probes for cellular antioxidants: Detection of NADH, hNQO1, H2S, and other redox biomolecules

Abstract

Maintaining redox homeostasis is critical for cellular function. To maintain a redox balance, a cell defense system that regulates the production of endogenous oxidants and antioxidants is of vital importance. Many biomolecules act as oxidants or antioxidants in cells and demonstrate complex crosstalk systems. Effective monitoring and detection of a given biomolecule are essential for understanding complex redox signals and related pathological properties. In this review, we outline recent advances in the development of small molecule-based fluorescent probes capable of detecting several representative antioxidants such as reduced nicotinamide adenine dinucleotide (NADH), human NAD(P)H:quinone oxidoreductase 1 (hNQO1) and H2S, and exploring complex crosstalk with other redox reactive biomolecules, including H2O2, HClO, SO2 and nitroreductase (NTR), by emitting fluorescence signals that are readily detected in vitro and in vivo. The basic design concepts involving small fluorescent molecules composed of a fluorescent reporter and recognition moiety that undergo a fluorogenic reaction in response to analytes are described. In addition, this review demonstrates the validation of such fluorescent molecules with a variety of biological models such as live cancer cells, cancer cell spheroids, tissues, mice, and zebrafish. Prospects for future directions are delineated by presenting the physiological importance of fluorescence-based detection of cellular antioxidants. © 2020 Elsevier B.V.