Conjugated Polyelectrolytes With Phosphorescent Metal Complexes: Design, Synthesis And Their Biological Applications

Conjugated polyelectrolytes (CPEs) are mainly composed of two important components, whichare π-conjugated backbones and water-soluble ionic side chains.“Molecular wires” can amplifysignal outputs, allowing for more rapid and efficient intra-and inter-chain excition migrations.Phosphorescent transition-metal complexes (PTMCs) have been widely used in the field ofbiological sensing and cell imaging, because they have outstanding photophysical properties, suchas tunable emission color, long emission lifetime, high quantum efficiency, large Stokes shift. Inthis thesis, PTMCs (as energy acceptor) were introduced into CPEs (as energy donor) to synthesizephosphorescent conjugated polyelectrolytes (PCPEs) for research of their photophysical propertiesand applications in biological sensing and cell imaging. The details are as follows.1. A series of hyperbranched-PCPEs containing different contents of iridium(III) complex andpolyfluorene units are designed and synthesized, in which blue fluorescene and red phosphorescenecan simply tuned by initial feed ratio of complex and fluorene. Their photophysical properties in thestate of solution and film are studied. The amphiphilic structure is in favor of the formation ofnanoparticles with the size of100nm. Electrostatic interaction between the nanoparticles andheparin influences the energy transfer between the polyfluorene units to Ir(III) complex, realizingthe ratiometric, naked-eye detection of heparin with good selectivity, high sensitivity. Time-resolved photoluminescence technique is used in the detection of heparin in the complicatedenvironment to improve the signal-to-noise ratio.2. PCPE containing a certain content of phosphorescent platinum(II) porphyrin, polyfluoreneand triphenylphosphine used to target mitochondria is designed and synthesized, whosephotophysical properties in the state of solution and film are studied. Because the phosphorescenceof platinum(II) porphyrin complexes can be quenched by oxygen through the energy transfer fromthe long-lived triplet excited state of complexes to the triplet ground state of molecular oxygen,PCPE as ratiometric oxygen probe is used to detect oxygen concentration quantitatively with goodsensitivity and naked-eye sensing. The cell imaging of HepG2cell in the state of air and hypoxiaare conducted. PCPE has also a specific labeling of mitochondria. Taking full advantage of longemission lifetime of PCPE, fluorescence lifetime imaging microscopy(FLIM) and time-gatedluminescence imaging(TGLI) are used to separate short-lived fluorescence signal from long-livedphosphorescent signal, improving the signal-to-noise ratio.