Synthesis Of A Ruthenium-containing Complexes And Its Application As A Colorimetric Probe For The Detection Of Biothiols

Biothiols, such as Cys (cysteine) and GSH (glutathione), play important biological roles in the human body. Metabolic disorder of these molecules have been linked to a number of diseases. The detection of these mercapto biomolecules in biological samples are very important for syndromes diagnosis and treatment. Campared to other analytical method, colorimetric method have advantages of simplicity, rapidity and low cost in biothiol detection. For the past few years, the development of colorimetric method for biothiol detection have made great progress, many dyes have been used to colorimetric detection of mercapto biomolecules. Recently, indicator replacement colorimetric method based on the competition mechanism between indicator and the analytes, has gained much attention. Ruthenium dyes possess special optical properties, they tend to have strong absorption in the visible area. In this work, we used bi(thiocyanato)-bis[N.N’-2,2’-bipyridyl-4,4’-dicarboxylic acid] ruthenium(Ⅱ)(known as N3dye) as indicator, developed a competition colorimetric assay for biothiols.Bi(thiocyanato)-bis[N,N’-2,2’-bipyridyl] ruthenium(Ⅱ) and bi(thiocyanato)-bis[N,N’-2,2’-bipyridyl-4,4’-dicarboxylic acid] ruthenium(Ⅱ) was synthesized from2,2’-bipyridyl and4,4’-dimethyl-2,2’-bipyridyl, respectively. The structures were confirmed by UV、MS and NMR spectra.A competition colorimetric assay for mercapto biomolecules cystein(Cys) and glutathione(GSH) based on the competitive binding with Hg2+between isothiocyano and thiol was developed by using N3as indicator. First, mercury ions coordinate to the sulfur atom of the dyes’NCS groups, and this interaction induces a color change (from red to yellow), owing to the formation of the Hg2+-N3complex. Then, in the presence of biothiols (such as Cys or GSH), the red color of N3is recovered concomitantly with the dissociation of the Hg2+-N3complex due to the extraction of Hg2+by biothiols. Thus the corresponding color variation in the process of the dissociation of the Hg2+-N3complex can be used for the quantitative detection biothiols through UV-vis spectroscopy. A good linear relationship in the range of0.5-25μM is obtained for both Cys and GSH, and the detection limits for Cys, GSH are57,52nM, respectively. This colorimetric assay displayed a high selectivity for cysteine over various other amino acids and GSSG (Oxidized glutathione).