Preparation And Application Of Organic Small Molecule Fluorescent Probes And Modified Polyionic Liquid Microspheres In The Near-infrared Region I

In the near infrared region II(NIR-II)imaging,light attenuation and scattering as well as background self-fluorescence are weak,so NIR-II imaging has good deep tissue penetration and high spatial resolution characteristics.So far,the materials used for NIR-II imaging are mainly inorganic nanomaterials,organic conjugated polymers,organic small molecules,etc.Inorganic nanomaterials have good adjustability and high quantum yield,but their raw materials are often biotoxic.Although organic conjugated polymers have low biological toxicity,they also have disadvantages such as slow metabolism and uncertain molecular weight.Organic small molecule probes have good development potential because of their controllable structure and easy adjustment,good biocompatibility,rapid excretion and no long-term toxicity.Therefore,we designed and synthesized Donor-Acceptor-Donor(D-A-D)type organic small molecule fluorescence probe with a new structure,but the problem of low fluorescence quantum yield still exists.We also introduced fluorene unit as a shielding unit(S)and synthesized S-D-AD-S type organic fluorescence molecule to improve quantum yield,it provides a new idea for the diagnosis and treatment of organic small molecule fluorescent probe in biology.Meanwhile,the effect of modified polyionic liquid microspheres as stationary phase in High performance liquid chromatography(HPLC)on drug separation was also investigated.The specific research content and results of this paper are as follows:(1)Generally speaking,the lower the energy gap value of organic fluorescent small molecules,the more successful the emission of NIR-II can be achieved.Since pyrrole and pyrrole dione(DPP)has a low band gap,strong electron acceptance,strong fluorescence and stability,so we introduced DPP as the receptor.It is also possible that the fluorescence quantum yield will be reduced when the energy gap value is too low,so the cyclopentanedithiophene with tetrahedral structure is introduced as the donor to regulate the electron distribution and energy band of the molecule,so as to reduce the fluorescence quenching caused by aggregation.D-A-D type organic fluorescent molecules were obtained by organic chemical reaction.In addition,in order to improve the fluorescence quantum yield of organic small molecules,S-D-A-D-S organic fluorescence molecules were synthesized by introducing fluorene unit as shielding unit(S)on the basis of D-A-D structural molecules.After characterization,both fluorescence molecules can achieve fluorescence emission in the NIR-II.(2)We also explored the multifunctional application of the prepared organic fluorescent probe in biology.Two organic small molecules,D-A-D type and S-D-A-DS type,were coated with liposomes to obtain hydrophilic nanoparticles(NPs).Compared with D-A-D type nanoparticles,S-D-A-D-S type NPs had higher fluorescence performance,the quantum yield increased to 0.82%.The penetration depth of S-D-A-D-S NPs can reach 15 mm,and it has good biocompatibility,good fluorescence imaging effect of liver,photoacoustic imaging effect and excellent photothermal treatment effect of tumor site.(3)We synthesized and sulfonated polyionic liquid microspheres,characterized the properties of the prepared new polyionic liquid microspheres,characterized the microspheres have good chromatographic performance,and further explore its application in drug separation as HPLC stationary phase.