Design And Application Of Red/Near-Infrared Mercury Probes

Heavy metals have a pollution effect on the environment,and then cause severe poisoning to living organisms and even the human body.Mercury,a typical heavy metal,interferes with the nervous system of the body and causes toxic effects after entering the body.In human production activities,mercury-containing waste is inevitably discharged.In the detection of mercury elements,the methods based on element analysis are the most inclusive,but they often involve expensive large-scale instruments,high energy consumption during atomization,and complicated operations.In the detection of mercury,the organic fluorescent dyes can be used to visualize the object in a luminous form.Organic fluorescent probes also have high sensitivity,high spatial resolution,real-time imaging,non-destructive biocompatibility,and can be modified according to different needs.In this study,two cases of fluorescent probes respond to Hg2+ were designed for different emission wavelengths,which the response wavelengths locate at the near-infrared region and the visible range.The main research conclusions are as follows:(1)CyS,a near-infrared fluorescent probe,that selectively responds to mercury ions in the aqueous phase was constructed using the commonly used cyanine dye IR-780 and a sulfur-containing dicarboxylic acid ligand.In the vitro tests,the mercury ion response behavior of CyS is mainly:In the neutral aqueous phase,CyS emited almost no fluorescence originally.After interacting with Hg2+,its emission at 790 nm was increased by more than 25 times.The fluorescence response behavior was not disturbed by common metal ions.In the thesis,we also carried out rigorous mathematical proofs on some of the subsequent useful conclusions.Studies have shown that CyS interacted with Hg2+through a 1:1 reversible complexation with a binding constant of 1.0×106 M-1,which can reflect the mercury ion content in the water phase in real time.Using it for the detection of Hg2+in living cells,CyS played low toxicity to living cells and Hg2+imaging in live cells was achieved,which fluorescence intensity was increased by more than 9 times under the Near-infrared fluorescence channel of microscope.(2)Based on two commercially available raw materials,4-chloro-7-nitrobenzo-2-oxo-1,3-diazole and 4-methyl-1-piperazineethylamine,a small molecule mercury ion fluorescent probe NBD-MPA,which relative molecular mass is less than 310,was obtained in a mild and simple one-step reaction.In preliminary tests,we obtained the response behavior of the probe NBD-MPA to mercury ions by UV-visible absorption spectra and fluorescence spectra.NBD-MPA exhibited a ratiometric fluorescence enhancement at 580 nm based on photoinduced-electron transfer(PET)that reversibly complexing with mercury ions.The ratio-type fluorescence enhancement reflected the mercury ion level in the water phase in real time.In a buffer solution under neutral conditions,it showed selective fluorescence response to mercury ions.Based on the small molecule characteristics of NBD-MPA,which has good chemical stability,in further attempts,we verified that the probe can be applied to a variety of conditions including mercury imaging in living cells,mercury imaging of zebrafish,mercury imaging of plant roots,and compatibility with response to mercury ions in real samples.Based the excellent selectivity and anti-interference ability on the response of NBD-MPA to mercury ions,which makes it possible to obtain better experimental results in many of the above applications.Anyway,the probe shows good performance on detection of mercury ions in both biological and aqueous phases.