Preparation Of Near-infrared Fluorescent Nanoparticles And The Application In Bioimaging

In recent years,the application of fluorescent nanoparticles(FNPs)in life sciences and biomedicines has been extensively studied.FNPs are widely used in the field of bioimaging because of their unique optical properties,mature preparation methods and easy surface functionalization.The advantages of FNPs based on Aggregation Induced Emission(AIE)materials are obvious in biological application,such as good stability,biocompatibility,resistance to photobleaching,low toxicity,high fluorescence quantum efficiency and so on.Near-infrared emission of FNPs is important in the bioimaging field.Because that near-infrared emission has low optical damage,strong tissue penetration,and less self-fluorescence of biological tissue.Deep-tissue fluorescence bioimaging technology has recently attracted widespread attention.Multiphoton fluorescence microscopy imaging technology is a alternative for deep-tissue fluorescence imaging method.Its excitation wavelengths are all located in the near-infrared region,which is beneficial to increase the tissue penetration depth of excitation light.In addition,due to the nonlinear excitation mode of multiphoton fluorescence,only the local particles focused on the beam will be excited,the region of bio-samples outside the beam focus cannot be excited,and it is able to reduce the possibility of photobleaching,as well as improve the spatial resolution of imaging.Based on these,we have prepared high-efficiency near-infrared fluorescent nanoparticles,and used them in multi-photon imaging,obtained good imaging results.1.Polymer encapsulated fluorescent nanoparticles for Three-phone imaging and Sentinel lymph node(SLN)mappingAIE molecule TB with red emission was encapsulated by four amphiphilic polymers PS-PEG,PSMA,PIMA and F127,and four kinds of polymer FNPs were obtained by ultrasonic self-assembly.The fluorescence quantum efficiency of PS-PEG@TB and PSMA@TB nanoparticles is as high as 27% and 20%,which were higher than nanoparticles encapsulated by PIMA and F127.TB has intramolecular charge transfer and solvating effect.The polystyrene hydrophobic chain of PS-PEG and PSMA can aggregate with hydrophobic AIE molecules to form a more hydrophobic core.It prevents water from inducing fluorescence quenching of dye.Therefore nanoparticles had brighter light.TB had good three-photon performance.The 1550 nm femtosecond laser was chosen as the light source to excite PS-PEG@TB nanoparticles,and a strong three-photon fluorescence signal was observed.The nanoparticle was used in vivo three-photon imaging of mouse brain and ear blood vessels.Imaging depths of 635 ?m and 180 ?m,respectively.The nanoparticles were also used for sentinel lymph nodes mapping of mouse.2.Near-infrared fluorescence nanoparticles base on resonance energy transfer effect for two-photon imagingThe near-infrared fluorescence resonance energy transfer(FRET)nanoparticle PSMA@TB/NIR775 was obtained by co-encapsulating the TB and the near-infrared fluorescent dye with the amphiphilic polymer PSMA.The nanoparticle has strong near-infrared(~780 nm)emission.Since TB had good two-photon performance,we excited the nanoparticles with a 1040 nm femtosecond laser as the excitation light source,and the 680 nm emission peak of the TB and the NIR775 780 nm emission peak excited by FRET can be obtained.Experiments showed that the nanoparticles had good monodispersity,stability,lower cytotoxicity and brighter near-infrared luminescence.The nanoparticle was used to perform two-photon imaging of mouse brain blood vessels.Imaging depth was about 150 ?m.