Fluorescent Probes with Multiple Binding Sites for the Discrimination of Cys, Hcy, and GSH

Abstract

Biothiols such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) play crucial roles in maintaining redox homeostasis in biological systems. This Minireview summarizes the most significant current challenges in the field of thiol-reactive probes for biomedical research and diagnostics, emphasizing the needs and opportunities that have been under-investigated by chemists in the selective probe and sensor field. Progress on multiple binding site probes to distinguish Cys, Hcy, and GSH is highlighted as a creative new direction in the field that can enable simultaneous, accurate ratiometric monitoring. New probe design strategies and researcher priorities can better help address current challenges, including the monitoring of disease states such as autism and chronic diseases involving oxidative stress that are characterized by divergent levels of GSH, Cys, and Hcy.

Nanoquencher‐Based Selective Imaging of Protein Glutathionylation in Live Mammalian Cells

“…[3] GSH and protein-SSG are therefore important biomarkers. [5][6][7][8][9][10][11][12][13] As the most abundant thiol in mammalian cells (1-10 mm), GSH could be readily imaged intracellularly despite the presence of other competing thiols (i.e.c ysteine and homocysteine); [9][10][11][12] al arge number of reaction-based, small-molecule fluorescent probes have been reported, some of which could even be used for realtime,q uantitative GSH imaging in live cells and tissues. [5][6][7][8][9][10][11][12][13] As the most abundant thiol in mammalian cells (1-10 mm), GSH could be readily imaged intracellularly despite the presence of other competing thiols (i.e.c ysteine and homocysteine); [9][10][11][12] al arge number of reaction-based, small-molecule fluorescent probes have been reported, some of which could even be used for realtime,q uantitative GSH imaging in live cells and tissues.…”

“…[5][6][7][8][9][10][11][12][13] As the most abundant thiol in mammalian cells (1-10 mm), GSH could be readily imaged intracellularly despite the presence of other competing thiols (i.e.c ysteine and homocysteine); [9][10][11][12] al arge number of reaction-based, small-molecule fluorescent probes have been reported, some of which could even be used for realtime,q uantitative GSH imaging in live cells and tissues. [13] Recent efforts have focused on fluorescent probes capable of imaging various thiols at spectrally distinct wavelengths. [13] Recent efforts have focused on fluorescent probes capable of imaging various thiols at spectrally distinct wavelengths.…”

“…[11,12] Most claimed GSH-selective probes are however universally thiol-reactive and possess poor selectivity over other endogenous thiols. [10,13] Athiol-unreactive yet GSH-selective imaging probe would have been more desirable,especially in cases where it is necessary to detect low-concentration endogenous GSH (e.g. [10,13] Athiol-unreactive yet GSH-selective imaging probe would have been more desirable,especially in cases where it is necessary to detect low-concentration endogenous GSH (e.g.…”

“…[13] Recent efforts have focused on fluorescent probes capable of imaging various thiols at spectrally distinct wavelengths. < 10 mm in human plasma compared to > 10 mm cysteine [13] ). < 10 mm in human plasma compared to > 10 mm cysteine [13] ).…”

“…[15] Although av ariety of gated MSNs are available to achieve on-demand intracellular drug release, [16] the use of antibodies as gatekeepers that enable antigen-responsive cargo release are extremely rare, [17] and to the best of our knowledge,s uch as ystem has never been reported for biosensor design. fluorescence ON state) only in the presence of sufficient GSH and/or protein-SSG that effectively compete for binding to the qMSN-bound antibody.Inits OFF state,however,the nanosensor would be non-fluorescent due to the qMSNshigh quenching efficiency toward the encapsulated dye.U nlike small-molecule GSH sensors, [9][10][11][12][13] our nanosensor would be inert to other endogenous biomolecules (including thiols). fluorescence ON state) only in the presence of sufficient GSH and/or protein-SSG that effectively compete for binding to the qMSN-bound antibody.Inits OFF state,however,the nanosensor would be non-fluorescent due to the qMSNshigh quenching efficiency toward the encapsulated dye.U nlike small-molecule GSH sensors, [9][10][11][12][13] our nanosensor would be inert to other endogenous biomolecules (including thiols).…”