Design, Synthesis And Application Of Fluorescent Probes Based On Disulfide Bonds

Disulfide bonds as an important functional group exist in a large number of chemical and biological molecules, such as the oxidized glutathione(GSSG), some protein(Thrombospondin-1 and protein disulphideisomerase PDI) and even some natural drugs(mitomycin disulfides and leinamycin). Disulfide bonds play a vital role in organisms, which are generally obtained by covalently crosslinking two cysteine residues. GSSG and GSH can maintain a balance of oxidation and reduction in cells, while disulfide bonds maintain mainly the stability of protein conformation to ensure their biological activity.Disulfide bonds can be interrupted by thiols, resulting in a mutual transformation of disulfide bond and mercapto group, and the ratio of GSSG/GSH can display the changes of redox state in cells. In human body, the cell contains a large number of free thiols, such as the concentration of glutathione in cells might reach to millimolar range(1-10 mM), and in blood plasma might reach to micromolar level(20- 40 ?M). Interesting, the concentration of GSH in cancer cells is much higher than the corresponding normal cells, which give us a inspiration in developing anti-cancer drug delivery system. Thus, in this paper, a novel strategy of drug delivery was proposed and the release of drug was real-timely traced by laser confocal fluorescence microscopy.Progress in our society is accompanied by environmental pollution, leading to increasing incidence of cancer. Sodium selenite(Na2SeO3) can effectively kill tumor cells, but its anticancer mechanisms are still unclear. In order to research the molecular mechanism of anti-cancer of Na2SeO3, we try to design and synthesize a novel fluorescence probe for detecting hydrogen selenide(H2Se), because the metabolism of Na2SeO3 in living cells can produce H2 Se. The probe contains a response group to H2 Se, a six-member cyclic moiety containing disulfide.Based on the above background, the structure of the paper is as follows.Section 1. We use a relatively new method to synthesize a near-infrared cationic amino merocyanine structure, and combine with chemotherapeutic drug camptothecin via disulfidecontaining linker to form a mitochondrial-targetable prodrug. Under simulated physiological conditions, the prodrug can be specifically interrupted by thiols, which leads to the release of active chemotherapeutic drug camptothecin and a signal of fluorescence enhance is observed.Because the concentration of GSH in cancer cells is much higher than the corresponding normal cells, most disulfide bonds of the prodrug in cancer cells can be interrupted by GSH with the rearrangement of intermediate and the release of the active anti-cancer drug camptothecin(CPT)at the same time. The fluorescence emission of the drug release process is in a near infrared region(at 702 nm), which is advantageous to avoid biological damage and backgroundinterference in living cells and in vivo.Section 2. In this section, we use the easier synthetic amino Hemicyanine structure as fluorescence precursor, and combine with disulfide-containing six-membered ring(oxidized DTT) as response group for H2 Se to synthesize a fluorescent probe which can specifically detect hydrogen selenide. Under simulated physiological conditions, the probe can be specifically interrupted by hydrogen selenide. Confocal fluorescence imaging of H2 Se in cells under hypoxic(1 % pO2) conditions was performed, which is contribute to explore the molecular mechanism of Na2SeO3-induced tumor cell apoptosis.