Development Of PH And HOCl Fluorescent Probes And Their Application In Environmental Analysis

As an important environmental influencing factor,pH greatly affects cell behavior in organisms and regulates many physiological and pathological processes.When the intracellular pH is abnormal,it will lead to dysfunction,which will cause various diseases such as inflammation and tumors.Hypochlorous acid?HOCl?is an important reactive oxygen species?ROS?with strong oxidizing properties.It is widely used in production and life and is one of environmental pollutants.HOCl is involved in the redox process in the cell and plays an important role in the immune system because it can resist pathogens and bacteria.However,when the level of HOCl in human body is abnormal,it will induce oxidative stress,leading to various diseases including arthritis and cancer,which will cause serious harm to human health.Therefore,the detection of pH and HOCl has caused great attention.Among the detection methods of the above two substances,the fluorescent probe method has many advantages such as good specificity,fast response,no damage to the detection sample,and it can be used for visual imaging inspection of biological samples by combining it with an optical microscope.So it is a very ideal detection method.Coumarin fluorescent dyes are widely used in the development and design of fluorescent probes as the parent structure due to their good optical properties such as high fluorescence quantum yield,excellent light stability and absorption and emission spectral shift in the visible light region.In this thesis,using coumarin fluorescent dye as a molecular platform,fluorescent probes CMFP-pH for pH and CMFP-HOCl for hypochlorous acid were constructed,respectively.1.By modifying the coumarin fluorescent dye,a new ratiometric pH fluorescent probe CMFP-pH and a highly selective HOCl fluorescent probe CMFP-HOCl were synthesized and their structure were well characterized and confirmed.2.CMFP-pH had good pH detection performance.In the detection,the protonation of the N atom in the quinoline group enhanced the ICT effect and resulted the ratio response to pH.As the pH decreased from 8.4 to 2.1,the absorption spectrum of the probe was red-shifted from 432 nm to 520 nm,the corresponding emission spectrum was red-shifted from 568 nm to 689 nm,the fluorescence emission ratio(I₅₆₈/I₆₈₉)changed from 15.8?pH 8.4?to 0.025?pH 2.1?.At the same time,the solution color changed from yellow to pink,and the corresponding fluorescence changed from blue-green to red.CMFP-pH has been able to quantitatively detect pH in the range of 3.5-4.6,with pKa value of 4.11.In addition,CMFP-pH showed high selectivity,reversibility,and low cytotoxicity to pH.Furthermore,it has been successfully used to image pH changes in living cells,Escherichia coli and zebrafish,exhibiting excellent potential for biological applications.3.CMFP-HOCl can specifically recognize HOCl.With the combined effect of freely rotating N-N single bond and the strong fluorescence quenching group2,4-dinitrophenylhydrazine,the fluorescence background of CMFP-HOCl was very weak.After adding HOCl,the aetohydrazide bond was specifically cleaved and the fluorophore was released.When 55?M of HOCl was added,the solution showed a20-fold enhancement in fluorescence emission.CMFP-HOCl had a good linear relationship with HOCl in the concentration range of 0-55?M.The detection limit was as low as 54.8 nM.CMFP-HOCl can respond to HOCl under physiological conditions and exhibited high selectivity.After it was made into a test strip,it can detect HOCl quickly and conveniently.In addition,CMFP-HOCl has been successfully used for the detection of HOCl in living cells and is an effective tool for exploring the biological function of HOCl.