Study On The Structure Regulation And Properties Of Several Novel Cyanide Fluorescent Probes

Cyanide is commonly used not only in industries including synthetic fibers,resins,metallurgy,electroplating,and herbicides but also in foods such as bitter almonds,apple seeds,cassava,sprouted potatoes,and so on.Cyanide can get into the human body through respiratory tract,skin contact,and ingestion,and can be absorbed by the lung and gastrointestinal tract of the human body.Consequently,absorbed cyanide inhibits the activity of enzymes in cells,affects the transfer of electrons in mitochondria,and damages the central nervous system,further causing respiratory arrest and death.However,endogenous cyanide in plants and animals can be used to defend against bacteria,fungi,and other pathogens,low concentrations of cyanide can stimulate cell proliferation.Therefore,sensitive detection of trace cyanide in food or organisms is of great significance.Among many methods,fluorescence analysis has been widely used in the detection of cyanide due to its advantages of high sensitivity,simple operation,and controllability of method.Fluorescent probes play a key role in fluorescence analysis of cyanide because chemical structures determine their properties.The structure of fluorescent probes determines their sensing performance to cyanide.For example,some probes show fluorescence quenching response,namely“Turn-Off” type,while some probes show fluorescence increasing response,namely“Turn-On” type,and some probes are ratiometric fluorescent probes.Therefore,the structural design of the fluorescent probe can regulate the response to cyanide.In this paper,based on the structural design of the fluorescent probe,the performances of the probe were constantly optimized,and the response behavior of the fluorescent probe to cyanide was therefore regulated.Consequently,the response ability of probe was gradually enhanced and the compatibility was improved,meanwhile,the probe has the function of targeting mitochondria of cell,which lays the foundation for its fluorescence imaging in vivo.The main contents are as follows:1.The current methods and progress of fluorescence analysis of cyanide were reviewed.The existence and toxic mechanism of cyanide in nature and industry were described.The existing determining methods and principles of cyanide were reviewed,and the response mechanisms of different types of fluorescent probes for sensing cyanide were introduced in detail.2.Two kinds of “Turn-On” fluorescent probes were designed.Based on previous studies,in order to transform the fluorescence response of triphenyl-malonitrile probe on cyanide from “Turn-Off” to “Turn-On” type,an electron-deficient group benzothiadiazole(BTD)was inserted into triphenyl-malonitrile(TPA-MT)molecule,which induced the TPA-BTD-MT probe to show “Turn-On” response for cyanide detection.To further investigate the influence of different structures of groups,we used an electron-deficient group of quinoxalinyl(DPQ)instead of BTD to obtain triphenyl-diphenylquinoxalinyl thiophenyl methyl-malononitrile(TPA-DPQ-TM-MT).In addition,triphenylcarbazole(NPC)was used instead of TPA to obtain triphenylcarbazol-diphenylquinoxaline-phenylmethylene malonitrile(NPC-DPQ-BY-MT).It was found that TPA-DPQ-TM-MT showed better response for cyanide with TPA as electron donor,MT as electron acceptor,and DPQ as an inserted electron-deficient group.3.A cyanide fluorescent probe with targeting and “Turn-On” response was designed.Based on the previous structural design and performance study,it was found that the probes with electron donor of TPA,electron-deficient group of DPQ,p-bridge of phenyl group,and electron acceptor of malononitrile exhibited better fluorescence response to cyanide.However,the molecules didn’t have targeting ability.Therefore,to make it have targeting ability,the pyridine group(Py)was used to replace MT group for obtaining the(E)-4-(4-(7-(4-(diphenylamino)phenyl)benzo[c][1,2,5]thiadiazol-4-yl)styryl)-1-methylpyridi n-1-ium(TPA-BTD-Py)fluorescent probe.The selectivity,anti-interference,targeting ability,and response mechanism of the probe to cyanide were studied systematically.The linear range for cyanide determination was 0.25-50 μM,and the limit of detection was 0.0462 μM.The probe was applied to the detection of cyanide in sprouting potato,cassava,bitter almond,and apple seeds and the recoveries of added standard solution were obtained ranging from91.41% to 103.8%,showing good analytical performance.To study the bioimaging ability of the probe,its cytotoxicity was first studied,showing a low toxicity effect.At the same time,the probe showed excellent fluorescence imaging for exogenous cyanide in Hela cells and good targeting ability on intracellular mitochondria.The probe also showed good fluorescence imaging ability when applied to the monitoring of exogenous cyanide by intraperitoneal injection in nude mice.Therefore,the probe has potential application value in the analysis and biological imaging of cyanide in food and organisms.