Synthesis And Application Of Fluorescent Probes For Detecting Intramolecular Small Molecular Thiols

Small molecular thiols, such as cysteine(Cys), homocysteine(Hcy), glutathione(GSH), burden important physiological function in living body. Their level is the vital standard whether an individual is healthy or not. Fluorescent probes have advantages of high sensitivity, high selectivity, convenient operation, and so on. As a consequence, it is of great scientific significance to design and synthesize probes for selectively detecting intracellular small molecular thiols. In this paper, we designed and synthesized two probes for thiols which were applied to image thiols in living cells. This dissertation is divided into three chapters.The first chapter mainly focuses on basic knowledge of fluorescence, main mechanism of fluorescent probes, the background of the research and the development of probes for small molecular thiols.In the second chapter, we designed and synthesized a new biothiol-selective fluorescent probe 1 based on photoinduced electron transfer(PET) mechanism. The UV-Vis absorption and fluorescent emission properties of probe 1 towards various analytes were studied in detail. The probe exhibited a large stokes shift(~200 nm) after reacted with biothiols and could selectively detect Cys in DMSO/PBS(9/1, v/v, 10 mM, pH 3.5) over GSH, Hcy, CN? and other amino acids with a detection limit of 0.124 μM. In addition, probe 1 responded well to GSH, Hcy and Cys in the same above solution with pH 5.5 and got the detection limits of 0.151 μM, 0.128 μM and 0.040 μM, respectively. Probe 1 was of very low cytotoxicity and successfully applied for imaging of thiols in living cells.In the third chapter, we prepared a near-infrared(NIR) turn-on fluorescent probe(NFC) based on chloroacetate modified naphthofluorescein for specific detection of Cys and Hcy over GSH and other amino acids(AAs) with the detection limits of 0.30 and 0.42 μM, respectively. The fluorescent intensity of naphthofluorescein(NF) chromophore is modulated by internal charge transfer(ICT) process. The probe NFC is readily prepared and weakly fluorescent, however, of observably enhanced fluorescence after reacting with Cys or Hcy. We demonstrated that the fluorescence off-on process involves a conjugate nucleophilic substitution/cyclization sequence. Furthermore, the probe has been successfully applied for detecting the total content of Cys and Hcy in human plasma and imaging in living cells with low toxicity.