| Small-molecule fluorescence sensor is a molecule whose fluorescence signal changes with the change of the properties of a substance in a particular system or environment.Compared with other analysis tools,small molecular fluorescence sensor has become a powerful tool for biological system research,because of its low cost,simple operation,high specificity,low detection limit and visual detection of target.In the past decade,two-photon microscopy(TPM),which uses NIR photons as excitation source,has become a new and indispensable imaging tool in biomedical research.Because TPM uses near-infrared light with focusing ability,it causes less light damage and photo-bleaching than the corresponding one-photon micro-imaging(OPM).Compared with OPM,TPM offers several advantages,including the capability of imaging deep inside a tissue,higher spacial resolution,longer observation time and so on.Compared with OP probes,TP probes have developed rapidly in recent years and have become an extremely important tool for detecting the microenvironment of life.Because of the extreme toxicity of cyanide in physiological systems,as well as the continuing environmental contamination caused by its widespread industrial use,posing a great threat to people’s health.The sensitive and selective recognition and detection of the cyanide ions are of great interest.Several methods for cyanide analysis often require time consuming pretreatment and the use of sophisticated instrumentation.Therefore,the design of chemosensors for specific recognition of CN-has been widely studied due to their inexpensive nature and rapid detection times.As a result,it has been actively studied in the past decade.Sulfur dioxide(SO2)is one of the main major atmosphere pollutants.Long-term exposure to SO2 not only causes some respiratory responses,but also induces lung cancer,cardiovascular disease and neurological diseases including migraine headaches,stroke and brain cancer.Inhaled sulfur dioxide is generally hydrated to produce sulfite acid in the respiratory tract and subsequently forms its derivatives of sulfite and bisulfite.Sodium sulfite is a common food ingredient that protects foods and beverages from oxidation;however,an excess sulfite can cause asthma and other allergic reactions in some individuals.SO2 and its derivatives are ubiquitous in our lives,but we know little about their biological role,because SO2 and its derivatives cannot be detected directly in vivo.High performance liquid chromatography(HPLC)is the most commonly used method for the determination of sulfite/bisulfite in biological samples,but it requires complex and invasive sample processing,not suitable for real-time and sustained detection of biological sulfite/bisulfite.Therefore,there is a need to develop a rapid,convenient and reliable real-time detection method of sulfite/bisulfite in biological level.Viscosity,as a crucial factor relating to diffusioncontrolled processes,plays an essential role in different biological activities,as well as in chemistry and other fields,and typically governs the rates of mass transport of reagents.Furthermore,the viscosity in the mitochondrial matrix is closely related to the respiratory state of the mitochondria via the molecular consequences of mechanically or osmotically induced changes in mitochondrial network organization,which suggests that changes in mitochondrial matrix viscosity may modulate metabolite diffusion and,in turn,mitochondrial metabolism.Through reading and investigating a large number of documents,this paper draws lessons from the work of our group and takes this as the basis.The two-photon probe L1 and L2,which can detect CN-and viscosity separately,and a ratiometric two-photon probe MBCB,which can double detect SO2 derivatives and viscosity were designed and synthesized.1.The carbazolyl derivatives L1 and L2 with two-dimensional chromophore structure were designed.The carbazole group was used as the parent,and the branched chain was introduced as the receptor unit at both ends.Two novel probe,L1 and L2,have been developed for the determination of cyanide and viscosity,respectively.The electron cloud density of nitrogen atom was increased by the deprotonation effect of-NH-by introducing nitrophenylhydrazine.The regulation of donor’s electron ability in chromophore 1 leads to the change of intramolecular charge transfer(ICT)in the whole system,which makes it possible to detect CN-by colorimetric method.The chemical sensor LI based on 2,4-dinitrophenylhydrazone has high selectivity and sensitivity to the detection of CN-,and the color change of the test solution from yellow to purple can be observed with the naked eye.The maximum UV absorption wavelength shifted from 440 nm red to 500 nm.The experimental results show that the chemical sensor L1 can detect CN-through the deprotonation process.The chemical sensor L2 forms an ICT state between the carbazole group and the cationic pyridine salt,which can be used as a molecular rotor and has a "turn on" fluorescence response to viscosity.There is a good linear relationship between the logarithm of viscosity and the logarithm of single-photon/two-photon fluorescence intensity.In addition,the results of two-photon confocal fluorescence imaging show that L2 has good membrane permeability and can be used for cell monitoring and imaging.2.A two-photon ratiometric fluorescence probe(MBCB)was designed and synthesized,which can detect SO2 derivatives and viscosity by different fluorescence signals.Using carbazole as parent,benzothiazole group was introduced into the frame of carbazole matrix,and the carbazole of electron donor and benzothiazole salt of electron absorption formed D-π-A structure.The compounds can react with SO2 derivatives through Michael addition mechanism and have high selectivity.Under the irradiation of ultraviolet lamp with 365 nm,the fluorescence color of the solution from peach red to purple could be observed before and after the addition of HSO3-.The sensitivity of MBCB to HSO3-was extremely high,and the detection limit was 0.81 nm.The carbazole group and methyl benzothiazole salt are connected by double bonds,which can be used as molecular rotors for viscosity detection.In addition,both sulfur dioxide derivatives and viscosity can be quantitatively measured by the ratio measurement method by adjusting the electron absorption ability of the two ends of the compound.MBCB has good two-photon properties and excellent biocompatibility.The fluorescence penetration depth in mouse liver sections can reach 130 μm,and can be targeted to mitochondria.Cell and zebrafish imaging experiments show that MBCB can effectively visualize the detection of HSO3-in mitochondria and in vivo zebrafish under two-photon excitation.As a ratio stoichiometric chemical sensor for measuring viscosity,MBCB can be used to quantitatively detect viscosity in solution or cell.The fluorescence lifetime imaging(MBCB)can be used to quantitatively analyze the viscosity distribution in cells.Drug induced mitochondrial apoptosis imaging experiment showed that the chemosensor MBCB could detect the changes of mitochondrial viscosity before and after apoptosis,and could judge whether the cells were apoptosis or not by detecting the changes of mitochondrial viscosity.It also provides a new direction for the study of apoptosis. |
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