Application Of Conjugated Polymer Fluorescence Probes In Biological Detection,Imaging, And Transfection

Conjugated polymers (CPs) have excellent optoelectronic properties owe to the delocalized π electrons on their backbones. In recent years, CPs have aroused great attention in interdisciplinary fields of chemistry, material, and biology. Through copolymerizing fluorene with low-band-gap monomer, polyfluorene derivatives with different emission color have been synthesized. Because of their unique advantages, such as high fluorescence quantum yield, high photostability, low toxicity, and easy side-chain modification, they are born to be promising materials for detections of biological molecules and biological imaging. The thesis is divided into three sections: The first part describes the detection of DNA by gel electrophoresis using conjugated polymers as colorful fluorescence probes; then, we focus on pH-responsive and near-infrared-emissive polymer nanoparticles for simultaneous delivery, release, and fluorescence tracking of doxorubicin in vivo; finally, we introduce conjugated polymer nanoparticles for gene silencing and intracellular tracking of siRNA release.Firstly, we investigate the interaction between conjugated polymers and biological molecules by gel electrophoresis. The results could be visualized using conjugated polymers as colorful fluorescence probes, and it is a promising method for multi-channel recognition of biological molecules simultaneously. We could distinguish single/double-stand DNA or DNA with different length or conformations according to the charge and steric hindrance of DNA/CPs complexes by gel electrophoresis.Secondly, we design a near-infrared-emissive conjugated polymer and used it to monitor anticancer drug Doxorubicin (DOX) delivery and release in a simple and easily detectable way. A pH-responsive nanoparticle crust is utilized to encapsulate BTTPF and DOX, and release drug in mildly acidic environment, such as tumor sites. The NIR fluorescence probe is able to indicate the drug release process through the change of FRET efficiency between DOX and BTTPF during degradation of NPs under acidic condition in vitro. NIR fluorescence signal with deep tissue penetration could also monitor in vivo drug delivery, as well as indicate drug release in a noninvasive and real-time way.Finally, we develop a siRNA carrier based on cationic conjugated polymer-siRNA nanocomposites (ThPFN/siRNA/BtPFN) by layer-by-layer electrostatic assembly technique. The fluorescence intensities of ThPFN and BtPFN change before or after assembly due to the FRET between them. Using the variation of FRET efficiency, we could monitor the intercellular release of siRNA in a label-free manner. Also, because the cationic ThPFN shell is able to protect the siRNA from the RNase and improve the cellular uptake efficiency, the ThPFN/siRNA/BtPFN nanocomposites are efficient and safe siRNA carriers.