The Preparation Of Near-infrared Fluorescent Probes Based On Semiconducting Polymer And Their Applications For In Vivo Fluorescent Imaging

In vivo fluorescent imaging technique is an important means for life science and fundamental medicine research,which highly depends on the properties of fluorescent probes.Fluorescence imaging with near-infrared(NIR)contrast agents possess high tissue penetration depth,high signal to noise ratio and sensitivity.Therefore,the development of novel NIR fluorescent materials is critical for in vivo fluorescent imaging.Semiconducting polymer dots(Pdot)possess many excellent properties,such as high fluorescence brightness,large Stokes shift,excellent stability and biocompatibility,which as an emerging organic fluorescence nanoparticles have been extensively used for biological applications.However,NIR-emitting Pdot are very rare,and most of them with weak emission.In our research,we synthesized and prepared Pdot that have high brightness and narrow-band emission at NIR region,and explored its applications in specific cell labeling,stem cell tracking,in vivo tumor imaging and lymph node mapping.The results of the research were shown as follows:1.A NIR dyes were doped into Pdot to prepare a high bright,narrow-band emission NIR Pdot.Due to efficient energy transfer from polymer to dye,the Pdot exhibit high brightness(quantum yield ~22%)at NIR region.The full width half maximum of the NIR Pdot is ~20 nm.In addition,the Pdot possess excellent high single particle brightness and excellent stability.2.Gel filtration chromatography was introduced to purify Pdot,which can efficiently decrease the cytotoxicity of Pdot.The purified Pdot was used to label mesenchymal stem cells(MSCs).The proliferation of MSCs was not affected by Pdot.The cytotoxicity of Pdot after long-term storage did not increase.After incubation with high concentration of Pdot,the pluripotent markers of MSCs were not affected by Pdot.3.A cell penetrating peptide(Octa-arginine,R8)was modified on the surface of Pdot,which promote the cellular uptake of Pdot.During short incubation time,low concentration of Pdot can label cells with high efficiency.The Pdot together with R8 are able to track stem cells over two weeks without disturbing their multipotent properties.4.The Pdot-labeled stem cells were transplanted into a liver-resection mouse model to study the in vivo cell tracking ability of Pdot.The MSCs can promote liver regeneration and the inflammation induced by liver resection was apparently decreased after stem cell transplantation.With the bright labeling,superior biocompatibility,and long-term tracking performance,the Pdot probes are promising for stem cell research and regenerative medicine.5.A near-infrared polymer that emitting at 800 nm were synthesized by incorporating a near-infrared porphyrin unit into polymer backbone.The polymer was prepared into Pdot by reprecipitation method.In specific cellular labeling,the Pdot exhibit higher labeling performance than the commercial probe,PE-Cy7.6.A blended NIR800 Pdot was prepared.Compared with the NIR800 Pdot,the absorption of the blended NIR800 Pdot shift to long-wavelength region and the brightness increased significantly.By modifing PEG groups onto the surface of the blended NIR800 Pdot,effectively decrease the uptake of reticuloendothelial system(RES)on Pdot,therefore extend the circulation time of Pdot in blood.The PEGylated Pdot were used as fluorescent contrast agent for lymph nodes mapping.Compared with the conventional dye staining method,the former shows higher signal to noise ratio and longer time window for imaging.The PEGylated Pdot exhibited long blood-circulation time and effectively accumulated to the lymph nodes and tumors,yielding high-contrast fuorescence mapping for precise surgery.