Design Of Ratiometric Chemsenors And Organelle-Targetable Fluorescent Probes

Fluorescent technique based on fluorescent dyes plays an important role in the field of life science. Fluorescent probes have been an important means of dealing with related problems in biology and basic medicine. However, most fluorescent probes are not targetable and don’t provide quantitative information, which can’t meet the needs of the observation of physiological process. In this paper, some fluorophores, such as BODIPY, Rhodamine and Naphthalimide, have been adopted to design ratiometric chemosensors and organelle-targetable fluorescent probes.1. Inspired from a chemodosimeter of rhodamine spirolactams, we reported a universal method to synthesize pure regioisomerical5-R-TMR and6-R-TMR such as5(6)-CO-TMR,5(6)-NO-TMR and5(6)-Br-TMR. Then on that basis, two FRET cassettes BRP1and BRP2have been designed and synthesized, which adopted regioisomerical5(6)-Br-TMR as acceptor and BODIPY as donor owing to its good overlap between absorption and emission spectra. BRP molecules, which display a sensitive solvatochromic effect in aprotic and protic solvents due to the ring-opening reaction of rhodamine spirolacton moiety, have been used to mornitor aprotic environment in MCF-7cells, and found out that there are relative high aprotic environments distributing in the regions around nucleus. To further proof the universality of BRP cassettes as a platform in design of ratiometric chemosensors, two kinds of ratiometric fluorescent probes, Hg-1and Hg-2, have been designed and synthesized on the base of BRP2. Hg-1and Hg-2display a high selectivity to mercury ion and large ratio changes. Compared with probe Hg-2, probe Hg-1shows higher sensitivity to mercury ion. The fast and drastic green-to-red color changes of Hg-1in intracellular Hg2+imaging could be clearly distinguished by using confocal fluorescence microscopy; this satisfied the requirement for real-time observations. A ratiometric nitric oxide BRP-NO has been designed and synthesized, which exhibits a fast response, high selectivity, visuable colour changes and large ratio changes. These results demonstrate that BRP cassettes as versatile platform can successfully design ratiometric probes for mercury ion, which provides new ideas for designing many ratiometric fluorescent probes for other analytes.2. Through Pd(0) catalyst and ’Click’ reaction, triphenylphosphonium (TPP) salt, a mitochondrion-targetable molecule, has attached to6position on2-carboxylbenzene moiety of6-Br-TMR. A mitochondrion-targetable probe Mito-Rh-NO has been synthesized, which displays a high sensitivity to NO. Mito-Rh-NO can be used for mornitoring endogenous and exogenous nitric oxide in mitochondria of living cells. Lysosome-targetable probes Lyso-NINO have been designed and synthesized through an integration of a NO-capturing o-phenylenediamine, a lysosome-targeting aminoethyl-morpholine and an efficient two-photon fluorophore naphthalimide. NINO has also been synthesized as reference compound. NINO and Lyso-NINO show a high selectivity and sensitivity to NO. Upon addition of NO solution, the two-photon cross sections of NINO and Lyso-NINO increase to200and250GM, respectively. Colocalized-staining demonstrate that Lyso-NINO is a perfect lysosome-targetable fluorescent probe for NO. With the aid of Lyso-NINO, the first NO’s capture within lysosomes of macrophage cells has been achieved in both two-photon fluorescent microscopy and flow cytometry.3. A membrane-targetable fluorescent probe Mem-BDP have been synthesized, in which positive charge of quaternary ammonium salt plays an important role in modulating the hydrophilcity of Styry-BODIPY dyes. Meanwhile, to some degree, this positive charge also damp ICT/salvation of Styryl-BODIPY dyes. With polarity of solvents, the red shift of Mem-BDP is smaller, and its fluorescent quantum yield is still high (up to0.3). Mem-BDP also can be used as a indicator to mornitor morphologic changes of membrane in cells in the presence of mercury ion. A mitochondrion-targetable FRET cassette BRPM has been easily obtained through methyl esterification of BRP. MCF-7cells incubated with BRPM show strong red fluorescence under a cofocal microscopy, which indicates that the energy transfer of BRPM is not affected by the microenvironment in cells. Moreover, BRPM in mitochondria exhibits a unique photochromic phenomenon. After irradiation of mercury lamp, mitochondria in MCF-7cells stained with BRPM show a unique and significant color changes from red to green under cofocal microscopy.