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Mercury is one of the most toxic and dangerous heavy metal elements.Mercury contamination is widespread and occurs through various processes,e.g.volcanic emissions, mining,solid waste incineration,and the combustion of fossil fuels.Of particular concern,is the concentration in the food chain,and bioaccumulation of mercury in animals.It is frightening that mercury-containing chemicals have been linked with a number of human health problems.Thus,much attention has been focused on developing new methods to monitor Hg2+ in biological and environmental samples.Recently,much method has been made to detect mercury.Fluorescent spectrometry is the most promising one.Compared with traditional methods for the detection of mercury,the fluorescent probes have attracted much attention over the years for its many inherent merits including high specifity and high sensitivity.This technology has been widely used for the real-time in situ detection of the molecular events both in the chemical and biological systems. Hence,exploring fluorescence sensors for detection of mercury in biological and environmental samples is one of the most important research subjects in supramolecular chemistry and biomedicine.Based on the previous work in our group,an improved fluorescent chemosensor for Hg2+, B2,was synthesized.In HEPES buffer solution,B2 exhibits selective fluorescence enhancement towards Hg2+ over other metal ions.The fluorescence enhancement was unaffected by anions existing in environment and organism because of the introduction of carboxyl-thiol moieties.B2 shows high sensitivity to Hg2+ in a concentration of ppb range with detection limit of 77 nM.B2-ester,the membrane-permeable ethyl ester,is able to be hydrolyzed to B2 in vivo,and successfully applied to image intracellular Hg2+ in living cells.In addition,different acyclic thioesters were intuduced into the fluorophore of rhodamine and a serious of Hg2+ sensors,R-A-E,R-A,R-OAe and R-OH were obtained.The four sensors showed fluorescence response towards Hg2+ in different degree.R-A shows high selectivity and sensitivity towards Hg2+,and the fluorescence enhancement is unaffected by other metal ions and anions.In a wide pH range,the response of R-A towards Hg2+ is unaffected by proton.The ethyl ester form of R-A,R-A-E,is successfully applied to image intracellular Hg2+ in living PC12 and Hela cells.
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