Application Of Fluorescent Probes Based On Triphenylamine-Based Dicyanovinyl Derivatives In The Determination And Bioimaging Of Cyanide

Photochemical technology is a common analytical method for the analysis of anion.Photochemical probes are widely used in clinical detection,environmental detection,food detection,and other fields because of their simple preparation,convenient operation,low price,stable performance,and sensitive detection of target substances.Cyanide ion CN~-)is a highly toxic anion and a trace amount of CN~-can quickly bond with cytochrome oxidase when it enters the body,blocking electron transport and thus causing vomiting,convulsions,unconsciousness and even death.The World Health Organization stipulates that the concentration of CN~-in drinking water should not exceed 1.9?M.Therefore,it is of great significance to construct photochemical sensor based on sensitive and selective fluorescent probes for CN~-detection in food,water,and biological systems.In this thesis,by changing their structures and controlling their response properties on cyanide,we designed and synthesized three fluorescent probes:triphenylamine-based dicyanovinyl compound 2-((4'-(diphenylamino)biphenyl-4-yl)methylene)malononitrile(TPA-MT),2-(4-(7-(4-(diphenylamino)phenyl)benzo[c][1,2,5]thiadiazol-4-yl)benzylidene)malononitrile(TPA-BTD-MT),and 2-(4-(8-(4-(diphenylamino)phenyl)-2,3-diphenylquinoxalin-5-yl)benzylidene)malononitrile(TPA-DPQ-MT).The responses of three fluorescent probes on CN~-from“Turn-off”to“Turn-on”type were compared and the response mechanisms were investigated.The constructed fluorescent sensors can be used for the determination and monitor of cyanide in food,cell imaging,biological living body,showing high sensitivity,good detecting capability,and excellent imaging performance.The main contents are introduced as follows:1.TPA-MT was designed with a triphenylamine moiety(TPA)as an electron-donating group,a dicyanovinyl group as an electron-accepting group,and phenyl group as a?-bridge.The response behavior of TPA-MT towards CN~-was studied by UV-vis spectrum and fluorescence spectra.The results show that the TPA-MT has good selectivity for CN~-in the THF and the fluorescence intensity decreases gradually with the increase of CN~-concentration,showing a"turn-off"response characteristic.With the determination of ~1HNMR and Job curve,the reaction site was revealed and the stoichiometry for TPA-MT-CN was 1:1.The fluorescence response grew linearly with the increase in the CN~-concentration from 0.25 to 6.0?M with the limit of detection(LOD)of 0.093?M.Furthermore,TPA-MT could be used to determine cyanoside in sprouting potato,indicating its practical application in CN~-detection.Bioimaging of TPA-MT towards CN~-in Beas-2B cells was investigated.The results showed that TPA-MT exhibited cell membrane permeability and the decrease in fluorescence in the presence of CN~-,realizing the monitor of CN~-at the cell level.2.Based on TPA-MT,a new probe of TPA-BTD-MT was designed and synthesized by inserted an electron-deficient benzothiadiazole(BTD)group into TPA-MT.The BTD group not only provides an efficient?-conjugation but also decreases the electron density at the?-position of the dicyanovinyl moiety in the TPA-BTD-MT molecule,improving the electrophilic nature of the dicyanovinyl unit.Consequently,the nucleophilic addition of CN~-at the?-position of the dicyanovinyl moiety in sensor TPA-BTD-MT was more effective than that in TPA-MT.The interaction between TPA-BTD-MT and CN~-was studied by UV-vis and fluorescence spectroscopy.The results show that the fluorescence intensity of TPA-BTD-MT intensively increases in the presence of CN~-,showing typical"turn-on"response.The recognition mechanisms between TPA-BTD-MT(and TPA-MT)and CN~-were investigated by absorption and emission spectroscopy,~1H NMR titration,and DFT calculation,which suggested that the fluorescence turn-on response of TPA-BTD-MT toward CN~-was induced by the localization of?-electrons and inhibition of intramolecular charge transfer(ICT).The sensor TPA-BTD-MT exhibited high sensitivity and selectivity for CN~-detection,with a linear range from 0.025 to 10.0?M and a limit of detection(LOD)as low as 0.087?M.The TPA-BTD-MT sensor showed appreciable accuracy when it was employed to determine CN~-in real food samples,including the sprouting potato,cassava,bitter apricot seeds,and apple seeds.Furthermore,the sensor showed low cytotoxicity for BEAS-2B cells and it could be used for imaging CN~-in living cells and animals with strong turn-on fluorescence.This study provides a new way for utilizing structural design to increase the specificity and sensitivity of the fluorescence sensor for the detection of cyanide.3.To further improve the biocompatibility and fluorescence response of the probe,a stronger electron-deficient group,2,3-diphenylquinoline(DPQ)group,was used to substitute for BTD to obtain a new fluorescent probe of TPA-DPQ-MT.Compared to TPA-BTD-MT,TPA-DPQ-MT not only exhibited a"turn-on"response but also showed faster response,lower detection limit,wider linear range,and higher sensitivity towards CN~-determination.The LOD is as low as 0.021?M and the linear range is 0.25-80?M.Importantly,TPA-DPQ-MT probe could be used to detect CN~-in 97%THF solution with LOD of 0.058?M and the linear range between 0.025 and40?M.Therefore,the TPA-DPQ-MT probe will be more promising for monitoring cyanide in living cells and animals.In conclusion,based on the structural design and controlling the fluorescence response,three fluorescent probes of TPA-MT,TPA-BTD-MT,and TPA-DPQ-MT were synthesized with the fluorescence changing from?turn-off”to“turn-on”response.The presented probes were successfully applied to detect and monitor cyanide in foods,water,living cells,and living mice,which provide an important basis for the construction of new photochemical sensors.