Tunable Heptamethine–Azo Dye Conjugate as an NIR Fluorescent Probe for the Selective Detection of Mitochondrial Glutathione over Cysteine and Homocysteine

Abstract

Although a lot of mitochondria-targeting biothiol probes have been developed and applied to cellular imaging through thiol-induced disulfide cleavage or Michael addition reactions, relatively few probes assess mitochondrial GSH with high selectivity over Cys and Hcy and with NIR fluorescence capable of noninvasive imaging in biological samples. In order to monitor mitochondrial GSH with low background autofluorescence, we designed a heptamethine-azo conjugate as an NIR fluorescent probe by introducing a tunable lipophilic cation unit as the biomarker for mitochondria and a nitroazo group as the GSH-selective reaction site as well as the fluorescence quencher. The probe exhibited a dramatic off-on NIR fluorescence response toward GSH with high selectivity over other amino acids including Cys and Hcy. Further application to cellular imaging indicated that the probe was highly responsive to the changes of mitochondrial GSH in cells.

An off-on fluorescent probe for specifically detecting cysteine and its application in bioimaging

“…In recent times, fluorescent molecular probes have emerged as an attractive tool for selective detection of various chemical and biological components [6][7][8][9][10], including thiols [11][12][13][14][15][16][17]. Compared to traditional techniques, chemical probes based on absorption or fluorescence changes are more feasible for detecting analyses owing to their many appealing advantages such as low detection limit, high selectivity, its real-time monitoring and its potential for vivo imaging of living cells.…”

Thiol-chromene click chemistry: A turn-on fluorescent probe for specific detection of cysteine and its application in bioimaging

“…Based on the nucleophilic substitution reaction of thiol and monochlorinated BODIPY moiety, the probe could detect GSH with ratiometric fluorescent emission whereas Cys and Hcy with turn-off fluorescent responses. Based on this mechanism, many probes for thiol have been developed [16][17][18][19]. However, the interference between Cys and Hcy could not be avoided.…”

Regenerative fluorescence “turn-on” probe for biothiols through Cu(II)/Cu(I) redox conversion

“…Considerable attention has been paid to the detection of biothiols using analytical techniques such as mass spectrometry [7], gas chromatography [8], and highperformance liquid chromatography [9] coupled with spectrophotometric or electrochemical methods. [10,11] Recently, fluorescent probes have been used for detecting biothiols due to their simplicity, high selectivity, and good sensitivity [12,13]. Most of fluorescent methods, however, are based on irreversible chemical reactions between the probe and the thiol providing only a single-use assay: Michael addition [14][15][16][17], cyclization with aldehyde [18,19], or a cleavage of sulfur-containing bond by the thiol [20].…”