Near-infrared Xanthene-cyanine Fluorescent Probes: Synthesis,biothiol Recognition And Cell Imaging

In recent years,fluorescent imaging probes have attracted the attention of researchers as an emerging detection method.Near-infrared fluorescence imaging technology has great space for development due to its strong tissue penetration ability,smaller damage to the sample,little background fluorescence interference and so on.Fluorescent probes were as molecular tools for bioimaging,and the core is the choice of fluorophores.The rhodamine fluorophore has the advantages of large molar extinction coefficient,high quantum yield and unique spiro structure control fluorescent switch.It is widely used in the construction of fluorescent probes,but its absorption and emission are located in the visible region,which is severely limited its application in bioimaging.The absorption and emission wavelengths of the cyanine-based fluorescent dyes are all located in the near-infrared region,but it has strong background fluorescence and poor water solubility when they used as fluorescence probes.Based on the above question,we designed and synthesized three near-infrared probe molecules,a glutathione fluorescent probe named Rh NM with long wavelength emission;cysteine fluorescent probe Ay SA applied in pure water solution;A near-infrared photosensitizer Cy OH for used as photosentizer in photodynamic therapy;the compound of three dyes were characterized by ¹H NMR,¹³C NMR,MS.1)In this paper,the near-infrared GSH probe Rh NM was designed and synthesized by the knoevenagel condensation reaction based on xanthene;the near-infrared water-soluble Cys probe was synthesized by retro-knoevenagel condensation reaction.Finally,near-infrared photosensitizer Cy OH in photodynamic therapy was synthesized.2)Glutathione plays an important role in human physiological activities,and its abnormal content is closely related to certain diseases of the human body,it is also crucial for their detection.Therefore,in this paper,based on the structure of xanthene,the rhodamine structure was re-modified to prolong the absoption and emmission wavelength to NIR region.2,2-(1,3,3-trimethylindolin-2-ylidene)-acetaldehyde was conjugated with rhodamine by Knoevenagel condensation to shift the wavelength to NIR region,The maleimidobenzoyl chloride was linked to rhodamine ethylenediamine by nucleophilic substitution reaction,then long wavelength glutathione fluorescent probe was constructed.The recognizition performance of probe was investigated and the results show that the probe can selectively recognize GSH with nake eye.The recognition mechanism is based Michael addition reaction and the GSH induced spiro ring opening,the emission wavelength reached to 746 nm and the quantum yield for 0.36.It can react with GSH in few minites,the p H range is wide,and the probe was also successfully applied in Hep G-2 cells for exogenous GSH imaging.In summary,the probe Rh NM can be used as a GSH sensor in an organism to quantitatively detect GSH content in physiological activities.3)Cysteine(Cys)can promote intracellular redox activity,heterogeneous metabolism and intracellular signal transduction.When the body lacks cysteine,it may accured growth retardation,liver damage,and even skin lesions et al.So the detection of cysteine in living organisms is of great significance.Therefore,this chapter designed and synthesized a novel near-infrared fluorescent probe for the detection of cysteine in pure aqueous solution.Sulfonic acid group was linked to cyanine fluorescent core used as water-soluble functional group,and an acryloyl chloride group as a recognition receptor for cysteine based on conjugate addition and intramolecular cyclization.The results showed that in a 100%aqueous solution,the probe showed a high discrimination against Cys in a few minutes and the emission wavelength reach to 701 nm.It has a wide p H range and fast response time for 5minites,and was applied in Bel-7402 cells for exogenous Cys imaging.Ay SA has a good application in detecting cysteine in tissues and animals.4)Photodynamic therapy is a new method for the treatment of tumors using photosensitizers and laser activation.Therefore,this chapter synthesizes a unique water-soluble heptamethine cyanine dye as a near-infrared PDT photosensitizer.Sulfonic acid was used as a water-soluble functional group,4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl moiety(TEMPOH)is used as a nitrogen-oxygen spin label to obtain biochemical reaction information in vivo.As expected,photosensitizers performed well in in vitro photodynamic therapy.It has low dark toxicity and large phototoxicity and high singlet oxygen quantum yield(??=16.96%).It has excellent cell uptake and good cell compatibility.It was successfully applied to near-infrared fluorescence imaging and AO/EB staining.In summary,Heptamethine cyanine dye used as a photosensitizer have great potential for cancer treatment in vivo,providing a new choice for the treatment of cancer.