A 3,5-dinitropyridin-2yl substituted naphthalimide-based fluorescent probe for the selective detection of biothiols and its application in cell-imaging

A mitochondria-targeted fluorescent probe for discrimination of biothiols by dual-channel imaging in living cells and zebrafish

Biothiols, including cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play distinct yet crucial roles in various mitochondrial physiological activities. However, due to their similar chemical structures, distinguishing and detecting Cys/Hcy/GSH poses a considerable challenge. In this study, we developed a dual-channel, mitochondrial-targeted fluorescent probe termed QX-NBD, designed specifically for discriminating Cys/Hcy from GSH. The incorporation of a quinolinium group endowed the probe with excellent mitochondrial targeting capabilities. This functionality arose from the positively charged group's ability to selectively bind to negatively charged mitochondrial membranes through electrostatic interactions. Additionally, the ether bond between 4-chloro-7-nitro-1,2,3-benzoxadiazole and the near-infrared fluorophore QX-OH rendered the probe susceptible to nucleophilic attack by biothiols. Upon the introduction of Cys/Hcy, the probe exhibited dual fluorescence emissions in red and green. Conversely, the presence of GSH resulted in only red fluorescence emission. The detection limits of the probe for Cys and Hcy at 542 nm in buffer solution were determined to be 0.044 μM and 0.042 μM, respectively. Similarly, the detection limit for all these biothiols was 0.028 μM at 678 nm. Furthermore, the response times for Cys/Hcy/GSH were recorded as 4.0 min, 5.5 min, and 9.5 min, respectively. Moreover, the probe was employed to monitor fluctuations in biothiol levels during oxidative stress in both HeLa cells and zebrafish, demonstrating its applicability and utility in biological contexts.

A lysosome-targeted fluorescent probe for thiol detection in drug analysis and multiple biological systems

Biothiols, characterized by their unique sulfhydryl (-SH) groups, possess excellent antioxidant properties, effectively neutralizing the damage to cellular structures caused by reactive oxygen species (ROS) in living organisms. Additionally, lysosomes play a crucial role in decomposing damaged biomolecules through the action of their internal enzymes, regulating the cellular redox state, and mitigating oxidative stress. To facilitate rapid monitoring of intracellular biothiols, particularly within lysosomes, we constructed a lysosome-targeted biothiol fluorescent probe, PHL-DNP, in this study. PHL-DNP exhibited excellent photophysical properties in an aqueous test system, including strong fluorescence enhancement response, excellent selectivity, and low detection limits (Cys 16.5 nM, Hcy 16.8 nM, GSH 21.3 nM, Cap 26.6 nM). These attributes enabled easy and efficient qualification of Cys on test strips and accurate determination of the effective content of captopril tablets. Notably, PHL-DNP demonstrated low cytotoxicity and precise lysosomal targeting. Through bioimaging, PHL-DNP not only monitored changes in biothiol levels under oxidative stress but also assessed biothiols in complex biological systems such as live HeLa cells, zebrafish, tumor tissue sections, and radish roots. This provides a promising tool for quantitative analysis of biothiols, disease marker detection, and drug testing.

1,8-Naphthalimide appended propiolate-based fluorescent sensor for selective detection of cysteine over glutathione and homocysteine in living cells

A novel 1,8-naphthalimide-based fluorogenic chemoprobe NASP was designed and developed as a sensor platform for the selective detection of biologically important cysteine over glutathione and homocysteine in living-cells.