Preparation And Two-Photon Imaging Of Fluorescent Oligo(P-Phenyleneethynylene) Nanoparticles

By the virtue of the unique conductivity, photo- or electroluminescence and fluorescence signal amplification, conjugated polymers or oligomers had extensively utilization in material and biological science. In recent years, conjugated polymer or oligomer nanoparticles(conjugated fluorescent nanoparticles) had gathered extensive focus in biological detection and imaging as a new class of fluorescent materials. Comparing to inorganic nanoparticles, conjugated fluorescent nanoparticles were preferred by such superiorities as easy synthesis, high quantam yield, good optical stability and biocompatibility. Moreover, conjugated fluorescent nanoparticles could be functionalized by conjugated backbone switch or the surface modification in different fields. In comparison with conventional single-photon microscopy mode, two-photon laser scanning fluorescence imaging was paid attetion by the deep tissue penetration, low photobleach and damage, and high optical resolution. Based on the fact above mentioned, we designed and synthesized three oligo(p-phenyleneethynylene)(OPE) based conjugated fluorescent nanoparticles. The property of self-assemble and photophysics were discussed afterwards. And the two-photon cell imaging was conducted as well in this paper.(1) Amphiphilic molecules oligo(p-phenyleneethynylene) derivative(OPE-PEG-NH2) with two-photon property, dipyrromethene derivaitve(BODIPY-C6Br) with green emission and polyfluorene-co-benzothiophene(PFDBT) with red emission were designed and synthetized. A series of conjugated fluorescent nanoparticles upon the self-assembly between amphiphilic molecules OPE-PEG-NH2 and BODIPY-C6 Br or PFDBT were prepared. And the optical behaviors of the nanoparticles infected by different FRET efficiency which were ralated to the different doping ratio of OPE-PEG-NH2 with BODIPY-C6 Br and PFDBT were discussed. Conjugated fluorescent nanoparticles were verified to have low cytotoxicity and could be utilized in two-photon cell imaging.(2) Oligo(p-phenyleneethynylene)-perylenebisimide(OPE-PBI) with two-photon property was designed and synthesized. The introduction of the long chain alkyl and rigid OPE effctively prevented the fluorescence quenching induced by the aggregation of PBI. The UV absorption spectra and fluorescence spectra were utilized in studying the optical properties of OPE-PBI in different solutions. And then the core-shell structure of OPE-PBI@DSPE-m PEG5000 were composed and characterized by DLS and TEM microscope. After that, two-photon cell imaging.were achieved by such nanoparticles above mentioned.(3) The two-photon amphiphilic molecule probe, OPE-2S-PEG, with disulfides was designed and synthetized by Sonogashira coupling reaction and amidation reaction. The optical stability of OPE-2S-PEG was discussed under different concentrations and p H values.. And the OPE-2S-PEG was confirmed to have specificity in thiol-containing molecules. After that, the detection of the introcellular thiols in Hela cells by OPE-2S-PEG was successfully accomplished.