Synthesis Of Near-infrared Second-region Organic Photosensitizers And Their Application In Phototherapy

Fluorescent probe imaging is a promising optical imaging technology in the field of biomedicine,which has the advantages of non-invasiveness,safety,strong visualization ability,high spatial resolution,and low cost.In basic biological research and clinical practice,fluorescence imaging technology in the visible region（400-700 nm）and the first near-infrared window（NIR-I,700-900 nm）has achieved rapid development and progress in the past decade.Although great progress has been made,NIR-I imaging still suffers from relatively low tissue penetration and inevitable tissue absorption and scattering,resulting in poor imaging results,deep tissue penetration and low spontaneous Fluorescence background imaging for further clinical applications still faces great challenges.Compared with the imaging in the visible light region and NIR-I,the imaging technology of the second near-infrared window（NIR-II,1000-1700nm）greatly overcomes the disadvantages of the former in imaging.The scattering and absorption of NIR-II light by biological tissues are greatly reduced,and the autofluorescence background of the tissues is at a lower level,thus giving NIR-II imaging a stronger penetration depth,higher resolution and confidence.Noise ratio and other advantages.Based on this,we developed two specific NIR-II fluorescent probes for the detection of trimethylamine（TMA）and hydrogen sulfide（H₂S）,respectively.The specific research contents are as follows:（1）In order to overcome the aggregation-caused quenching（ACQ）effect caused by the hydrophobicity of ZS-1010 molecules,weaken the intermolecular stacking,and improve the fluorescence quantum yield,we designed and synthesized a NIR-II Nanoparticle fluorescent probe ZS-1010-PEG.ZS-1010-PEG has a stable nanoparticle size.The existence of PEG chains can effectively avoid fluorescence quenching caused by aggregation effect,and obtain excellent fluorescence quantum yield.It is expected to use the EPR effect of biological tumor tissue to realize tumor cell imaging.（2）A novel organic small molecule NIR-II fluorescent probe ZS-1010 for TMA detection was designed and synthesized.A strong D-π-A electronic"push-pull"structure was formed inside the molecule,and it had The lower energy gap makes ZS-1010 molecules have strong absorption and emission in the NIR-II region.Under the excitation of 980 nm light,the ZS-1010 molecule will generate a charge transfer process from the donor（D）to the acceptor（A）after absorbing photon energy,and generate NIR-II fluorescence in the form of radiative transition.After TMA was mixed,TMA with strong electron-donating properties would inhibit the intramolecular charge transfer process of ZS-1010,and the molecular dipole moment would change,resulting in fluorescence quenching.（3）Design and synthesis of a NIR-II fluorescent probe Et-1080 for the detection of H₂S gas signal molecules.Compared with common cyanine dyes,Et-1080 is due to the benzene ring attached to the indole ring,making it With a larger conjugated structure and a lower energy gap,the maximum fluorescence emission can reach 1060 nm,and it has excellent fluorescence quantum yield and molar absorption coefficient.The electron-deficient Et-1080 molecule is converted by D-π-A strategy.The part and the electron-donating part are connected by aπ-conjugated system,and the nucleophilic addition reaction between H₂S and the C=C double bond on the electron-deficient indole leads to the destruction of the molecular conjugated structure,resulting in the fluorescence quenching of the Et-1080 molecule.The change of the fluorescence signal realizes the detection of H₂S.