Preparation Of Sulfur Dioxide Fluorescent Probe And Its Application In Biomedical Imaging

Fluorescent probes have been widely used in the fields of biology,medicine and environmental sciences since they came out in the 1990s because of its advantages in selectivity,sensitivity,detection limit and biological damage.The working principle of fluorescent probes is mainly to achieve the purpose of monitoring target substances through changes in color or fluorescence properties.Based on these characteristics,fluorescent probes play an irreplaceable role in the in-situ monitoring of biosignal molecule metabolism in living systems.Sulfur dioxide（SO₂）is a common gaseous pollutant.According to research reports,SO₂may be the fourth small gas messenger molecule,which exists mainly in the form of bisulfite and sulfite in the body.Endogenous SO₂ can be produced by the metabolism of amino acids such as cysteine.Moderate concentration of SO₂ can regulate cardiovascular and venous relaxation in vivo.SO₂ in mitochondria plays an important role in myocardial injury and mitochondria swelling and deformation induced by isoproterenol.In addition,the studies had shown that SO₂ directly forms the environment for mitochondrial synthesis and increase in the brain by studies.However,the concentration of SO₂ is closely related to metabolic abnormalities and those with cancer,neurological disorders.Based on this,we have read a lot of literature and designed three relevant fluorescent probes.And it was characterized by NMR and HRMS.The response performance of these three probes to SO₂ and the positioning performance of mitochondria were explored through spectral test and cell imaging test.In general,a series of meaningful research results have been achieved.The thesis research mainly includes the following contents:（1）This paper designed and synthesized a turn-off SO₂ fluorescent probe TH-SO₂.The probe combines benzothiazole and quinoline salt,and uses unsaturated C=C as the recognition site for sulfur dioxide.The probe has a large conjugation system and strong green fluorescence.When it is combined with SO₂,the conjugation system is blocked,and the green fluorescence is quickly quenched,thereby achieving the purpose of detection.In the spectrum test,the probe showed good characteristics such as strong ion selectivity and p H adaptability.Based on this,we performed cell imaging experiments and zebrafish imaging experiments on the probe to test its performance in detecting SO₂ in living organisms.According to the experimental results,the probe not only has low cytotoxicity,but also has excellent performance in the detection of exogenous sulfur dioxide in cells and zebrafish.In the mitochondrial colocalization experiment of the probe,the Pearson correlation coefficient of the probe reached more than 90,proving that the probe has good targeting performance to mitochondria.In addition,this probe is currently one of the few turn-off SO₂ fluorescent probes.（2）This paper designed and synthesized a turn-on probe Co-SO₂.The probe Co-SO₂uses coumarin as the fluorescence platform and the C=C as the recognition site to detect sulfur dioxide based on the Michael addition reaction.The probe is pink when dissolved in a buffer solution which shows weak fluorescence intensity.After responding to SO₂,the ultraviolet absorption changes obviously,the fluorescence intensity increases,and it emits strong green fluorescence.The probe has a higher response multiple,lower detection limit,wide p H adaptability and good ion selectivity in spectral test data.In cell experiments,the probe Co-SO₂ showed low cytotoxicity,good mitochondrial targeting function,and the co-localization coefficient with Mito Tracker Red was as high as 92.In addition,the color change of the probe before and after the reaction with SO₂ can be observed with the eye.（3）This paper designed and synthesized the fluorescent probe Na-SO₂ with the naphthalimide fluorophore.The probe Na-SO₂ combines many advantages of naphthalimide with good light and thermal stability,large Stokes shift and special rigid structure.It is a near infrared fluorescent probe based on Michael addition reaction with carbon carbon double bond as recognition site of SO₂.Experimental data shows that the probe has a certain corresponding effect on SO₂ and has a good targeting function on mitochondria.