Design,Synthesis And Fluorescence Imaging Study Of Fluorescent Probes For Detecting Cyanide And Ferrous Iron

Cyanide is a highly toxic reagent that can lead to death in a very small dosage,which,however,is also an important industrial raw material applicable to fields like metallurgy,electroplating and synthetic fibers.The annual output of industrial cyanide all around the world is as high as 150,000 tons,resulting in cyanide-containing wastes that may contaminate the environment and threaten the existence or health of humans and animals.Meanwhile,cyanide is also available in some foods.The long-term intake of a large amount of cyanide-containing food would lead to cyanide poisoning.Therefore,it is in urgent need of developing fluorescent probes that can detect cyanide in the environmental as well as in biological samples.Iron is one of the most common elements in biological bodies.Studies have shown that iron is involved in various critical biochemical processes during the metabolism of biological cells,such as oxygen transport,electron transfer,enzyme activity and DNA synthesis.Early symptoms of some serious diseases are usually expressed by the abnormal iron concentration.The iron in living cells mainly exists in ferrous iron form.Therefore,the levels of iron in living cell can be reflected by sensing the concentration of ferrous ions.Hence,it is of great significance to develop fluorescent probes for real-time monitoring of ferrous ion in biological cells.Herein,the fluorescent probes for detecting cyanide and ferrous ion have been designed and developed respectively in this paper,and the specific research contents are shown as follow:Firstly,construction of the fluorescent ratiometric probe for cyanide based on intramolecular electron transfer?ICT?mechanism.In this probe,the coumarin fluorescent dye was used as the fluorophore and the electron-deficient conjugated double bond was employed as the specific recognition site for cyanide.after reacting with 90?M cyanide,the fluorescence emission wavelength of the probe displayed redshift from 570 nm to 608 nm,and the fluorescence emission ratio increased from 0.52156 to 4.21472 with the detection limit calculated to be 0.24?M,which is far lower than the cyanide concentration in drinking water provided by the World Health Organization.The probe exhibited excellent selectivity towards cyanide and hardly interfered by other common anions.Finally,the application of the probe to sensing cyanide in water samples and living cells was successfully demonstrated.Secondly,a coumarin-based fluorescent probe for monitoring labile ferrous iron in living system.The coumarin fluorescent dye is adopted as the fluorophore and C=N bond is used as the fluorescent modulating group of the probe.Before the reaction with Fe²⁺,the probe itself possesses almost no fluorescence due to the rotation and isomerization of C=N.However,upon reaction with Fe²⁺,the Fe²⁺-mediated cyclization reaction will be conducted for the probe molecule,thus inhibiting the rotation and isomerization of C=N bond and triggering fluorescent enhancement of the probe.Spectroscopic experiments have shown that strong fluorescence can be observed at 452 nm in case of the reaction between the probe and Fe²⁺,the process of which can be completed within two minutes.At the same time,the probe responded to Fe²⁺with high selectivity and sensitivity,and its detection limit is 45 nM.Finally,it is verified that the probe can successfully be applied to the detection of Fe²⁺in biological cells.