Synthesis And Properties Of Thiols-based Fluorescent Probes

Fluorescent probes have the advantages of good selectivity, high sensitivity, short response time, used in cells and organisms as well as the advantages of simple operation,simple synthesis and low cost, which makes it had a extensive application in the fields of biochemistry, medicine, pharmacology, life sciences, environmental chemistry. Aliphatic thiols play a very important role in the physiological activities of the human body.Typically, the changes in the content of aliphatic thiols which include glutathione(GSH) , homocysteine (Hcy) , cysteine (Cys) are associated with many diseases,such as leukopenia, psoriasis, liver damage, cancer and AIDS. Thiophenols are a class of highly toxic and pollutant compounds. Generally, exposure to thiophenol liquid and vapor was reported to cause a series of serious health problems, including central nervous system damage, increased respiration, muscle weakness, hind limb paralysis, coma, and even death.Because of the similar structure and reactivity of mercapto amino acids, making it more difficult to selectively detect a certain mercapto amino acid without being affected by other effects. Therefore, it is a challenge to design a fluorescent probe that can accurately and specifically detect one of the mercapto amino acids. At the same time,because thiophenol and aminothiophenol have relatively similar structure and reactivity,an effective method is needed to selectively detect one of the thiophenols.Specific work content is as follows:We developed a cyanine-based near-infrared fluorescent probe utilizing 4-amino thiophenol as a detecting group, which showed the fluorescent "turn-on" response towards GSH and it can be used as a biomarker to determine the cellular GSH.We found that the commercial available cyanine dye IR-780 had a remarkable capability of determining the amino-substituted thiophenols. Especially, the 2-amino thiophenol induced a fluorescence change of this cyanine dye with the largest intensity in comparison to the 3- and 4-amino thiophenols, implying Cyanine IR-780 can distinguish 2-amino thiophenols from position isomers. Despite the 2-amino thiophenol quenched the fluorescence of cyanine dye, their complex system further played a role in detecting the glutathione with high selectivity over cysteine and homocysteine. It was worth mentioning that similar selectivity can also be observed in living cells.We developed a 4-Chloro-7-nitrobenzo-2-oxa-1,3-diazole ( NBD-C1) based fluorescent probe. The fluorescent probe is simple to synthesize and can selectively recognize homocysteine and cysteine under different conditions,which is free from interference by other acids.