Construction And Biological Applications Of Fluorescent Probes For Selective Detection Of Sulfur Dioxide Derivatives

Fluorescent probe is mainly used to achieve qualitative or quantitative analysis of specific targets through its color or fluorescence intensity changes.It has a series of advantages such as high sensitivity,high selectivity,short reaction time and quick operation,et al,making it increasingly significant in environmental pollution sources,life sciences and other fields.Compared with single-photon fluorescent probe,two-photon?TP?fluorescent probe excited by the visible or near infrared wavelength?about 700-1100 nm?,can overcome the problems of many single photon fluorescent technology,such as short excitation wavelength?350-550 nm?,light bleaching,light damage and cell fluorescence,et al.Thus,fluorescent probes have aroused wide interest in scientific research and has become a hot topic in frontier field.Furthermore,due to the maximum emission of the near-infrared?NIR?fluorescent probes lie in the long wavelength region?600-900 nm?,which has the capacity of deep tissue penetration and can effectively reduce the light damage to organisms,NIR fluorescent probes have a good application prospect in the field of molecular imaging.Although many fluorescent probes have been reported to test molecules,ions and environmental parameters in cells,most of them still have problems in stability,specificity and other aspects.Therefore,it is of great significance to design and synthesize new fluorescent probes to test bio-molecules,ions and environmental parameters in cells with high selectivity and sensitivity.In this research,Naphthalimide and coumarin derivatives were selected as fluorophores respectively.Three kinds of fluorescent probes were designed and synthesized for the detection of sulfur dioxide?SO₂?and its derivative bisulfite sodium?NaHSO₃?.Firstly,we designed the probe Na-SO₂-Lyso to discriminate SO₂ and its derivatives based on the fluorophore of 1,8-naphthalimide with the aldehyde group C=O as the reaction site.In addition,the morpholine unit was attached to the probe to locate lysosomes.The initial fluorescence of Na-SO₂-Lyso is weak due to the non-radiative decay process of the excited state caused by the isomerization of C=N.When treated with HSO₃^-,its specific chemical transformation can generate strong hydrogen bond donor of-OH group.As the newly generated intramolecular O-H···N=C hydrogen bond effectively inhibited the C=N isomerization of Na-SO₂-Lyso,the fluorescence intensity of thr probe greatly enhanced and effectively realized the detection of NaHSO₃.In the biological imaging experiment,the probe was able to detect NaHSO₃ in HeLa cells and zebrafish under one-photon and two-photon modes.Secondly,the probe NIR-SO₂-TP was designed and synthesized based on coumarin group with carbon-carbon double bond as reaction site of bisulfite or sulfite.Its NIR emission wavelength ranges from 790 to 900 nm.When bisulfite is added to the probe,the conjugate system of C=C bond is cut off based on nucleophilic addition and the green fluorescence of coumarin with TP profile is released.Thus,a probe NIR-SO₂-TP with both NIR and TP profile was obtained for the detection of SO₂.Moreover,the probe can detect NaHSO₃ in cells,tissues,zebrafish and mice under NIR and TP imaging modes.Last,CoB-SO₂,another NIR and TP probe,is further developed based on difluoroboroxy coumarin fluorophore.The probe CoB-SO₂ exhibits NIR emission at 650-800 nm.while upon the addition of HSO₃^-,the?-conjugated system was cut off,leading to the red fluorescence quenching and the green fluorescence of coumarin group release.Therefore,the probe can discriminate sulfur dioxide with good selectivity and fast response.In biological experiments,imaging of SO₂ in cells and zebrafish were carried out.