Construction And Property Study Of AIE Nanoprobe With Red/Near Infrared Emission Based On Pyrene

Red/near-infrared(R/NIR)emission(620～900 nm)has lots of advantages,like low energy,deep tissue penetration and high signal-to-noise ratio.Materials with R/NIR emission have been widely used in bioimaging.Meanwhile,fluorescence materials with aggregation-induced emission(AIE)characteristic also have many advantages such as high luminous efficiency,excellent photostability and good biocompatibility.Developing a nanoprobe which has R/NIR emission and AIE characteristic is important for bioimaging.However,only a few nanoprobes have been reported,because of the difficulty of the design and preparation of R/NIR dyes.In this paper,two strategies,F?rster resonance energy transfer(FRET)and chemical modification were adopted.Nanoprobes with both R/NIR emission and AIE characteristic were successfully constructed,which could be as a reference for the design of nanoprobes.The study contains two parts.In the first part,R/NIR emissive QPNR-PLGA nanoparticles were prepared by physical methods,namely FRET.In the second part,BPCN nanoprobe with long-wavelength emission was obtained by chemical modifications of bis-pyrene(BP)with electron-withdrawing groups.In the first part,we utilized FRET strategy to obtain a R/NIR emissive nanoprobe.Firstly,a new dye quadri(pyrene)(QP)with AIE characteristic was designed and synthesized.The molecular structure was determined by MALDI-TOF mass spectrometry and nuclear magnetic resonance spectroscopy.Then,the optical properties were studied by ultraviolet-visible absorption spectroscopy and fluorescence spectroscopy.QP exhibited AIE characteristic in CHCl3/Et OH.The emission peak of QP nanoparticles was at 510 nm in Et OH.Then,using nanoemulsion method,QP-PLGA nanoparticles with the emission peak at 510 nm were prepared in water.Similar to the preparation of QP-PLGA nanoparticles,a series of QPNR-PLGA nanoparticles were obtained mixing different molar ratio nile red(NR)into QP.FRET existed in QPNR-PLGA nanoparticles,which was proven by fluorescence emission spectrum,fluorescence excitation spectrum and microplate reader.Eventually,the nanoprobe,QPNR-PLGA nanoparticles,could emit fluorescence in the range of630-670 nm.In the second part,a new dye BPCN with AIE characteristic was designed and synthesized byintroducing electron-withdrawing groups cyano(CN)into BP skeleton.The structure of BPCN was determined by electrospray mass spectrometry,proton and carbon nuclear magnetic resonance spectroscopy.Then,the optical properties of BP and BPCN were studied by ultraviolet-visible absorption spectroscopy and fluorescence spectroscopy,validating that BPCN had AIE characteristic,and the emission peak of BPCN was at 620 nm.The two-photon properties of BPCN and application in cell imaging were explored.Above study showed that the chemical modification strategy enhancing the donor-acceptor(D-A)effect by introducing a strong electron-withdrawing group CN could effectively redshift the emission wavelength of BP.In following study,BP introducing strong electron-donating group diphenylamine or dihexylamine was designed to increase the intramolecular D-A effect.Thereby,R/NIR emissive AIE nanoprobes were expected.