Design,Synthesis And Application Of Organic Fluorescent Probe In Detection Of Hg²⁺

Mercury ion(Hg2+),as one of the most common toxic heavy metal ions,can be seen everywhere in industry,agricultural production and daily life,especially in a variety of food types.Hg2+ can enter crops through the soil,and enter the human body through the food chain,such as drinking water,and accumulate continuously.Once it exceeds the limit that the human body can tolerate,it will induce a series of diseases,not only gastrointestinal ulcers,diarrhea,pulmonary edema and other problems,and will cause damage to the central nervous system of the human body,and even cause death due to respiratory failure,endangering human health.With the gradual improvement of people’s requirements for living environment and food quality,environmental pollution and food safety incidents caused by heavy metals have also received increasing attention.Therefore,it is urgent to establish a new and reliable detection method with high sensitivity,high selectivity and simple operation for the qualitative and quantitative detection of Hg2+ in the environment and food.In this thesis,organic fluorescent probes characterized by simple synthesis,high sensitivity,high selectivity,fast response time and simple operation were constructed for the detection of Hg2+.Two different organic fluorescent probes were constructed by rational design and their structures were characterized.The spectral characteristics of two organic fluorescent probes were explored by fluorescence spectroscopy,and the two probes were applied to the detection of Hg2+in domestic water.Based on the poor water solubility of the organic fluorescent probe 1,it was not used for cell imaging experiments,but the organic fluorescent probe 2,which was successfully water-soluble,was applied in the imaging of biological samples and lung cancer cells.Research work in the following areas:(1)Taking Hg2+as the research object,based on the principle of protection and deprotection of aldehyde groups,a new organic fluorescent probe(probe 1)was designed and synthesized by a one-step synthesis method,which can achieve high selectivity and high sensitivity for Hg2+detection.Probe 1 was synthesized using 6-hydroxy-2naphthaldehyde and 1,2-ethanedithiol as raw materials to obtain a naphthalene dithiolane structure through acetal protection.In the absence of Hg2+,the probe 1 itself has almost no fluorescence emission intensity;while in the presence of Hg2+,the naphthalene dithiolane structure is destroyed,thereby releasing the fluorophore 6-hydroxy-2naphthaldehyde,This makes the detection system appear fluorescence turn-on phenomenon.When probe 1 was incubated with different concentrations of Hg2+,with the gradual increase of the concentration of Hg2+,the emission peak was significantly enhanced at 515 nm,and showed a good linear relationship in the range of Hg2+concentration of 0-20 μm,and its detection limit as low as 1.27 nM.After the probe 1 was assisted by dimethyl sulfoxide,it was applied to the detection of Hg2+ in actual water samples,and the detection results showed a good application prospect,but it needs to be assisted by organic solvents,which is not conducive to actual biological samples,especially In vivo imaging assay analysis.(2)Considering the problem of poor water solubility and biocompatibility of the above synthesized probe 1,through a reasonable design,hexaethylene glycol with good water solubility and biocompatibility was introduced for water-solubility modification.In order to realize actual sample detection and in vivo imaging detection in pure water system.The synthetic route is as follows:using hexamethylene glycol as a raw material to prepare p-methylsulfonylated hexamethylene glycol,and reacting with 6-hydroxy-2naphthaldehyde in the presence of potassium carbonate to generate a new compound.The intermediate obtained above reacts with 1,2-ethanedithiol to generate a new probe(probe 2)with better water solubility.Firstly,its fluorescence spectral properties were studied.After incubation of probe 2 with different concentrations of Hg2+,it was observed that its emission peak was enhanced at 460 nm,and the increase of fluorescence value had a good linear relationship with the concentration of Hg2+.The detection limit is as low as 0.62 nM.The test results show that,compared with probe 1,probe 2 not only has enhanced water solubility,but also saves the components of co-dissolving organic solvent,and almost has no cytotoxicity proved by MTT staining method,which can be well used for Cell Imaging Analysis.(3)Considering the excellent water solubility and biocompatibility of the abovementioned probe 2,the successfully water-soluble modified probe 2 was then applied to actual sample detection and imaging analysis.First,the digested crayfish meat and serum samples of blood mercury patients were used as actual detection samples to carry out research.The results showed that in the standard addition test of crayfish meat,the recovery rate of Hg2+detected by probe 2 was all within the national standard.The test results are within the standard range of the method and the test results have good reproducibility;probe 2 is used to detect the Hg2+content in serum samples of blood mercury patients.Compared with the national standard method,the detection amount of Hg2+in serum samples obtained more accurate results.Subsequently,probe 2 was further used in the imaging analysis of the lung cancer cell(HepG2)model,and good imaging results were obtained,indicating that probe 2 can be used for the detection and imaging of Hg2+in living cells,so that it can be better applied to biology in the future.The qualitative and quantitative detection of Hg2+ in samples has laid a good foundation.