Design,Synthesis And Optical Properties Of Fluorescent Probes Based On Benzopyrans

As an active oxygen species,hypochlorite mainly produced by hydrogen peroxide and chloride ions in the peroxidation reaction of myeloperoxidase(mpo)in organisms,and it plays a strong antimicrobial role in killing many pathogens.However,excessive hypochlorite can lead to many diseases such as cardiovascular disease,atherosclerosis,osteoarthritis,rheumatoid arthritis,lung injury and even cancer.Cysteine is a major sulphur-amino acid and plays an important role in many biological processes,such as tissue growth and cell antioxidant defense.Abnormal levels of intracellular cysteine are also associated with many diseases,such as sleepiness,slow growth,liver damage and AIDS.Sulfur dioxide has long been taken into account as an environmental pollutant.Epidemiological studies have shown that exposure to sulfur dioxide not only causes many respiratory reactions,but also is associated with lung cancer,cardiovascular diseases and many neurological diseases.Hydrazine can be used as high-energy fuel in missile and rocket propulsion.It is also widely used as one of the important industrial raw materials for the production of paints,pharmaceuticals,emulsifiers and pesticides.Although hydrazine plays an important role in industrial production and real life,the use of hydrazine often causes some damage to the environment and organisms.The United States Environmental Protection Agency(EPA)has listed hydrazine as a possible carcinogen and recommended a threshold of 10 ppb(310 nM)for hydrazine.Some of these small molecular compounds exist in organisms and some are commonly used in routine production.However,the concentration of these compounds was too high in organism,or long-term exposure to environments containing large amounts of these compounds,will cause certain health damage to organisms.Therefore,it is important to quantitatively detect hypochlorite,cysteine,bisulfite and hydrazine in physiological environment,cells and even organelles with fluorescent probes.This paper is divided into four parts,as follows:1.Probes 3-4 based on chromenylium and pyrene were designed and synthesized and used for the detection of hypochlorite.These two probes showed turn-on response towards hypochlorite,and the fluorescence intensities can be enhanced 90 and 200 times respectively.What's more,the two probes showed high selectivity towards hypochlorite and low detection limits(probe 3:32.1 nM,probe 4:114.8 nM).In addition,probe 3 had a fast response time(within 130 s),and it made probe 3 become a potential fluorescent probe for practical applications.2.Chromenylium derivatives with acrylate unit(probes 9-10)were designed for the selective detection of cysteine in this paper.The optical properties of probes 9-10 towards cysteine were evaluated in different pH values.Probes 9-10 showed large turn-on signals(50/25-fold enhancement)at pH=7.4 when they were treated with cysteine;the response times of the probes towards cysteine were 11 min and 24 min,the detection limits were calculated as low as 9.5 nM and 11.0 nM.While probes 9-10 exhibited 7.5-fold and 4.2-fold fluorescence enhancements towards cysteine respectively at pH=5.0;the response times towards cysteine(100 equivalent)were more than 4 hours,and the detection limits were calculated at 809.4 nM and 923.1 nM.Moreover,they exhibited a high selectivity for cyeteine in neutral or weak acidic conditions.Furthermore,cell imaging studies demonstrated that probes 9-10 were lysosome targetable compounds of cysteine in HeLa cells.3.Chromenylium skeleton can respond to hypochlorite and bisulfite simultaneously,its affects their selectivity.To avoid the influence of hypochlorite,a probe(probe 13)with tetrahydroxanthylium and coumarin units was designed for the detection of bisulfite.Probe 13 showed obvious color change from blue to yellow and a large turn-on signal(144-fold enhancement)with green emission towards bisulfite.Moreover,the response time of probe 13 towards bisulfite was within several seconds order,and the detection limit was calculated at 22.8 nM.Fluorescence co-localization studies demonstrated that probe 1 was a mitochondria-targeted fluorescent probe for the bioimaging of bisulfite in HeLa cells.4.Chromenylium is a good recognition unit of bisulfite.Therefore,when chromenylium derivatives are used as fluorophores,the conjugate structure of the fluorophores will be destroyed under the attack of high concentration nucleophilic reagents.To avoid the influence of nucleophilic reagents on fluorophores of chromenylium derivatives,fluorophore 15 based on methylchromenylium was designed and synthesized.And then probe 17 based on fluorophore 15 was prepared for the detection of hydrazine.As a contrast,fluorophore 16 based on chromenylium and corresponding probe 18 were designed and synthesized.The results show that fluorophore 15 and probe 17 were more tolerant to nucleophilic reagents than fluorophore 16 and probe 18.Whhat's more,probe 17 showed a large turn-on signal(25 fold enhancement)towards hydrazine,the response time was 30 min and the detection limit was calculated at 110 nM.Furthermore,probe 17 can be applied to the detection of exogenous hydrazine in HeLa cells.