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UBC Theses and Dissertations

Development and characterization of semiconducting polymer dots for applications in bioanalysis Lix, Kelsi


Semiconducting polymer dots (Pdots) are rapidly gaining popularity as fluorescent probes in bioanalysis and imaging. These materials have several remarkable and highly advantageous properties, including their extremely high per particle brightness, large one- and two-photon absorption cross sections, biocompatibility, and ease of preparation. However, being a new material, Pdots suffer from several key limitations that must be addressed before they may find widespread use in bioanalysis. Pdots are typically synthesized by the manual nanoprecipitation method which suffers from poor control and reproducibility. Although energy transfer-based chemical and biological sensors have been developed using Pdots, their photophysics and mechanisms of energy transfer are poorly understood, limiting the rational design of such sensors. Being held together by relatively weak entropic forces, Pdots are only moderately stable and are often prone to non-specific binding due to their surface chemistries. To date, relatively few surface and bioconjugate chemistries have been reported. This thesis presents the development of a novel, flow-based synthetic method for Pdots yielding improved reproducibility, tuneable particle sizes, and the ability to synthesize Pdots on small (1 mL) and large (100 mL) scales. A comprehensive study of energy transfer between Pdot donors and organic dye acceptors is also presented, and considers the frameworks of Förster Resonance Energy Transfer (FRET), Dexter energy transfer, and photoinduced electron transfer (PET). The results suggest that FRET alone is not sufficient to describe energy transfer in such systems, and that Dexter ET and PET likely also contribute. Thirdly, a surface coating material based on dextran, a biosynthetic glucan, was used to functionalize the Pdot surface and enabled preparation of immunoconjugates using tetrameric antibody complexes (TACs), resulting in improved performance in proof-of-concept immunoassay and cellular imaging applications. Overall, this thesis presents key contributions to the development of Pdots for applications in bioanalysis, including their synthesis, a deeper understanding of their photophysics, and enhanced performance in biosensing and imaging.

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