UBC Theses and Dissertations
Red luminescent polymer nanoparticles : synthesis and applications in sensing and bioimaging Christopherson, Cheyenne
Emissive polymers offer unique features over small molecules for applications in biological imaging and sensing. The ability to define polymer architecture and molecular weight through highly controlled polymerization methods allows for the development of materials such as nanoscale drug carriers, temperature-responsive matrices, and emissive polymer nanoparticles. This work centers around the controlled synthesis of emissive polymers with highly defined molecular weight through two living polymerization methods: Cu(0)-reversible deactivation radical polymerization (RDRP) and ring-opening metathesis polymerization (ROMP). Phosphorescent iridium(III)-based polymers were synthesized by Cu(0)-RDRP, and the kinetics of this polymerization are discussed in detail. The resulting polymers exhibited narrow molecular weight distributions and emission in the blue, green, and red regions. As heavy metal-based emitters often have low biocompatibility, purely organic materials based on a 1,8-naphthalimide (NAI) acceptor exhibiting thermally activated delayed fluorescence (TADF) were prepared and incorporated into star polymers. The addition of a water-soluble, biocompatible monomer, Nisopropylacrylamide (NIPAM) and a blue fluorescent emitter resulted in water-soluble polymers with temperature-controlled emission colour. Next, additional red TADF monomers based on NAI acceptors were developed for ROMP, which allows for the facile synthesis of block copolymers with highly defined interfaces. These monomers were incorporated into amphiphilic diblock copolymers with a guanidine-rich hydrophilic block, and a hydrophobic block resembling the emissive layer of organic light emitting diodes (OLEDs). These diblocks self-assembled into polymer dots (Pdots) in water, where the guanidine-rich corona provided excellent shielding ability of the encapsulated emitters and allowed for efficient uptake into multiple cell lines. The covalently bonded TADF dyes eliminated the previously seen problem of dye leakage from Pdots, and these materials were successfully used for cellular imaging. Lastly, highly rigid TADF emitters based on BPPZ acceptors were synthesized and incorporated into Pdots to improve brightness and photostability. These TADF emitters were encapsulated into guanidine-rich Pdot matrices as small molecules, allowing this system to act as a model for hydrophobic drug encapsulation. Confocal imaging with cancer cell lines was performed to evaluate the internalization of the Pdots, and it was demonstrated that the length of the guanidine corona affects the internalization of the Pdots by HeLa and Jurkat-T cells.
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