Research On Conjugated Polymer Nanoparticles Derivated From Poly (9,9-dioctyfluorene) As Fluorescence Probe

In recent years, semiconducting conjugated polymer nanoparticles(CPNs) have emerged as a new class of extraordinarily bright fluorescent probes that exhibit exceptional fluorescence brightness, good photostability, fast radiative rate, nonblinking behavior, low cytotoxicity, and fascile surface-modification. CPNs have gained considerable attention in the field of chemical, materials, biological and medicine. However, the photon-limiting interference is a key problem in their practical applications. CPNs in the red to near-infrared region(600-1100 nm) are highly desired. It is owing to their minimal photon-limiting interference, for example, backscattered laser light, absorption, and autofluorescence in biological tissues. In addition, red CPNs show comparably deep tissue penetration. Thus, we reported work about developing red fluorescent CPNs.(1) We inquired the experiment conditions of how to prepare CPNs. Through adjusting the experiment parameters, we prepared CPNs based on poly[9,9-dioctylfluorene-co-2,7-bis-(2-thienyl)-9-fluorenone] with different nanoparticle sizes, and found that the sizes of CPNs prepared by reprecipitation is smaller compared with the sizes of CPNs prepared by miniemulsion. Photophysical properties revealed that the larger the nanoparticle size of CPNs is, the more red-shift the photoluminescence spectrum of CPNs is.(2) A novel orange-red fluorescence probe based on poly[(9,9-dioctylfluorene-co-fluorenone](PFFO) nanoparticles with narrow emission band was developed. The original signalization function is based on efficient F?rster Resonance Energy Transfer from PFFO to Rhodamine B(Rh B) dye molecules. This novel probe exhibited a large Stokes shift(~ 210 nm), enhanced photostability and longer lifetime compared to Rh B dye molecules. Meanwhile, it displayed the characteristics that especially useful in live cell or in vivo studies, such as narrow full width at half-maximum emission(FWHM ~ 40 nm), excitation bands in the visible range and the sensitivity of its fluorescence to temperature within 10-50 oC. In addition, the cost of this orange-red fluorescent probe is low. Confocal fluorescence images of the fluorescent probe proved that it could effectively label He La cells.(3) We prepared red CPNs based on hyperbranched polymer,which show high quantum yield of 22 %. The(3-(4,5- dimethylthiazol-2- thiazolyl)- 2, 5-diphenyl-2-H-tetrazolium bromide assay results indicated that the CPNs based on hyperbranched polymer had low cytotoxicity and fine biocompatibility for biological applications. The confocal images demonstrated the red CPNs based on hyperbranched polymer not only could effectively label He La cells, but also expressed application potential in oxygen sensing. The red emission intensity of CPNs based on hyperbranched polymer decreased remarkably with an enhancement in oxygen concentration, and red light quenched when it in atmosphere(oxygen concentration is about 21 %).