Design, Synthesis And Properties Of Biothiol And Hydrazine Hydrate Ratiometric Fluorescent Probe

Cysteine（Cys）,glutathione（GSH）and homocysteine（Hcy）are the three most abundant small-molecule compounds in biological thiols.Because of their specific redox properties and nucleophilicity,their abnormal content can cause cataracts,neurodegenerative diseases,autoimmune diseases,etc.,so they are of great significance in human health and disease.Hydrazine（N₂H₄）is generally used in preservatives,rocket propellants,pesticides,foaming agents and polymerization inhibitors,etc.It is also a kind of neurotoxin or carcinogen.Exposure to it can cause irreversibly damage to the central nervous system,lungs and liver of the human body.Therefore,the differential detection of biological thiols and hydrazine hydrate are of great significance.Fluorescent probes are widely used because of their simple operation,fast efficiency,and high resolution.In recent years,there have been a number of fluorescent probes on the detection of biothiols,hydrazine hydrate,but most of the"on-off"type is easy to be affected by the instrument and concentration,while the ratiometric fluorescence sensor can better eliminate the interference of the probe concentration and instrument changes,so as to have higher detection accuracy.The focus of this paper is to identify fluorescent probes for the detection of biological thiols and hydrazine hydrate.The main contents are as follows:（1）In this paper,NAPh1,NAPh2,DEACou1,DEACou2,DEABF,Julo BF,THQBF were designed and synthesized to study how to inhibit fluorescence resonance energy transfer（FRET）and photoinduced electron transfer（PET）when the strong quenching group NBSe was used as the recognition group process.On the one hand,we used 7-diethylaminocoumarin as the fluorophore and NBSe as the recognition group to study the effect of the length of the non-conjugated chain between the fluorophore and the recognition group on the PET process.On the other hand,using 4-amino-N-（4-hydroxyphenethyl）benzamide as the linker,diethylamino fluoride boron,julolidine fluoride boron and tetrahydroquinoxaline fluoride boron were introduced to study the influence of fluorophore electron donating ability on PET process.During the study,we found that the probe THQBF and DEACou2 didn’t undergo PET process and were able to detect the three biothiols in a ratiometric manner.（2）In the study of how to inhibit PET by using NBSe as recognition group,we found that the fluorescence of probe THQBF and DEACou2was not quenched,and the emission wavelengths were 650 nm and 469 nm,respectively.In contrast,the probe TQBF could achieve single-wavelength excitation and have a good deep tissue penetration ability,but the wavelength difference between the probe and biothiol before and after response was not obvious,so only the ratiometric detection of GSH.DEACou2 could detect Cys,GSH and Hcy with dual-wavelength,but its disadvantages were strong background fluorescence interference,poor tissue penetration and cumbersome operation.In order to be better applied in biological imaging,we designed and synthesized a single-wavelength excitation ratiometric fluorescent probe TQBF-NBS using NBS as the identification group and tetrahydroquinoxaloline fluoroboron dye as the fluorophore.The fluorescence emission wavelength of the probe was 650nm,and it had deep tissue penetration ability.The large Stokes shift（230nm）could avoid the self-absorption and internal filtration effects.DEACou2 and TQBF-NBS had good selectivity and anti-interference,and they had been successfully applied in biological imaging experiments.（3）Based on the intramolecular charge transfer mechanism（ICT）,the ratiometric fluorescent probe MA-N₂H₄ was designed and synthesized to detect hydrazine hydrate（N₂H₄）using naphthalene ring as fluorophore and1,3-indandione as recognition group.The fluorescence emission wavelength of the probe was 670 nm,and it had a large Stokes shift（200nm）and long emission shift（230 nm）.In addition,the probe MA-N₂H₄had high sensitivity,good selectivity,low detection limit（0.5μM）and short response time（18 min）,which could be successfully used to detect N₂H₄ in living cells and zebrafish.