Phenothiazine-based Fluorescence Probes For The Detection Of Hypochlorous Acid And Sulfur Dioxide Derivatives

Cell redox homeostasis,which refers to the dynamic equilibrium state between oxidizing and reducing species in cells.is an internal defense mechanism.The imbalance of redox homeostasis caused by exogenous or endogenous stimuli may interfere cells’normal physiological function,resulting in a variety of diseases.In cells,hypochlorous acid（HCl O）is one of the important reactive oxygen species,while sulfur dioxide derivatives(SO₃^2-/HSO₃^-)are important active sulfur species.The combination functions of them play a leading role in cell redox homeostatic state.In this paper,a highly water-soluble fluorescent probe PG for HCl O detection and a fluorescent probe DP for HCl O and SO₃^2-/HSO₃^-continuous detection were designed and synthesized based on the basic method of fluorescence detection and the principle of molecular recognition.Probe PG was synthesized by conjugating N-methyl phenothiazine-3-formaldehyde and glucosamine.Herein,glucosamine was chosen because of its excellent water solubility and biocompatibility.In PBS buffer（containing98%H₂O）,PG was stale for at least 30 h,and displayed highly selective,high sensitive detection towards HCl O with a low detection limit（5.2μM）and a fast response（less than 4 s）.Importantly,probe PG featured a large Stokes shift（148 nm）and this enabled it to avoid background fluorescence interference effectively.PG was successfully applied in HCl O detection in various water samples.In probe DP,phenothiazine used as the electron donor and 2-（3-cyano-4,5,5-trimethylfuran-2（5H）-alkyl）malononitrile as the electron receptor.In PBS buffer（containing 90%H₂O）,with the addition of HCl O into DP solution,the thioether unit was selectively oxidized into sulfoxide structure（DP=O）,accompanied by the fluorescence increasement at 608 nm.The detection limit of probe DP for HCl O was calculated to be 89.5 n M and the response time was found to be less than 120 s.Moreover,the sensing ability of DP to HCl O cannot be interfered within the physiological p H range（p H=5.8-8.0）.Further study shown that the carbon-carbon double bond of DP=O can undergo a further nucleophilic addition reaction with SO₃^2-/HSO₃^-with a quenching fluorescence phenomenon.Interestingly,DP exhibited no response to SO₃^2-/HSO₃^-.The detection limit of DP for SO₃^2-and HSO₃^-was calculated to be 70.8 n M and 65.1 n M,respectively.Due to its advantages of high specificity,sensitivity and short response time(within 600 s for SO₃^2-and within 150 s for HSO₃^-).Probe DP responsed to HCl O and SO₃^2-/HSO₃^-based on"Dual-key-and-one-lock".Model DP has been successfully applied for the detection of HCl O and SO₃^2-/HSO₃^-in live zebrafish and nude mice.