The Constructon Of A Novel Fluorescent Probe For Sulfur Dioxide Derivatives And Its Application

For a long time,sulfur dioxide（SO₂）has been considered as a toxic gas,whose main source is the incomplete combustion of fossil fuel,and when SO₂meets with water in the air,acid rain forms.Excessive inhalation of SO₂can cause a variety of diseases,such as respiratory diseases.With the further study of SO₂,researchers found that SO₂ is also a"double-edged molecule",which can be spontaneously generated in biological systems and it is one of the important metabolites containing sulfhydryl（-SH）amino acids,such as Cys.Endogenous SO₂ has certain benefits for the human body,such as balancing the redox reaction,regulating the cardiovascular smooth muscle tone and the muscle strength of the heart in the body.However,the physiological and pathological functions of SO₂ in vivo are still unclear,which needs the continuous efforts of researchers.Excellent detection methods and powerful detection tools will be very conducive to the research of researchers.Fluorescent probe imaging technology is an analytical method to identify bioactive molecules through the change of fluorescence signal,like the intensity or displacement of fluorescence signal.Compared with the traditional detection methods,fluorescent probe imaging technology has unique advantages,such as excellent selectivity and sensitivity,nondertructive,in situ detection,and so on.In this paper,based on the literature investigation,we constructed three novel fluorescent probes with targeted properties,which are expected to further realize the detection of SO₂ in human body.Firstly,based on xoxanthracene as the fluorescence platform and the double bond as the recognition site of SO₂,we have synthesized a near infrared and mitochondrial targeting SO₂ fluorescent probe XA-SO₂.Due to its high molar extinction coefficient,good fluorescence quantum yield and excellent photostability,as well as its strong intramolecular charge transfer（ICT）effect,the probe has a near-infrared fluorescence signal.When the probe XA-SO₂reacted with Na HSO₃,the conjugated system was destroyed,and fluorescent intensity gradually decreases with the increase of Na HSO₃,to achieve the purpose of identifying the SO₂.Furthermore,the fluorescence probe XA-SO₂successfully detected He La extracellular/endogenous SO₂,and the probe XA-SO₂ can effectively enrich on mitochondria of cells,which is expected to achieve the dynamic detection of SO₂ in mitochondria of cells.Secondly,naphthalimide as the fluorescence platform and aldehyde group as the recognition site of SO₂,we have synthesized a novel endoplasmic reticulum-targeted and―turn on‖fluorescent probe CA-SO₂.The fluorescence of the probe itself is weak due to the non-radiative transition of C=N isomerization.When the aldehyde group reacted with the Na HSO₃ derivative based on nucleophilic addition,the hydrogen bond donor-OH was generated,it can form O-H···N=C,thus effectively inhibiting the C=N isomerization and enhancing the fluorescence signal,thus achieving the recognition of SO₂.In addition,biological experiments have shown that the probe can recognize He La extracellular and endogenous SO₂ derivatives.Finally,based on benzopyran as a fluorometric platform and the double bond as the recognition site of SO₂,we have synthesized a novel mitochondrial targeting fluorescent probe MA-SO₂.The probe has red fluorescence signal emission.When Na HSO₃ was added,the conjugated system of MA-SO₂ was destroyed,leading to the weakening of fluorescence signal with the increase of NaHSO₃ concentration,so as to achieve the dynamic detection of SO₂.In addition,biological experiments of the probe showed that the probe has the ability to recognize He La extracellular and endogenous SO₂.In conclusion,we designed and synthesized three kinds of targeted SO₂fluorescent probes.These probes are expected to be effective tools for the detection of SO₂ derivatives in biological samples,and also provide theoretical guidance for the design of relevant fluorescent probes.