Hybrid Organic Materials Comprising Polymers and Small Molecules for Biodiagnostic and Electronic Applications

Brian Richard Stepp

doi:https://doi.org/10.21985/N2FJ02

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Hybrid Organic Materials Comprising Polymers and Small Molecules for Biodiagnostic and Electronic Applications

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This thesis focuses on the design of hybrid organic materials comprising polymers and small molecules for biodiagnostic and electronic applications. Specifically, the electrochemical and fluorescent signaling properties of terthiophene-functionalized polymers are combined with the enhanced recognition properties of DNA hybrid materials, culminating in the development of a "loaded" probe for amplified DNA detection. Poly(norbornene) with pendant terthiophene side chains was synthesized such that oxidative cross-linking of the terthiophene groups led to new polymeric materials with enhanced thermal stability. Films of the cross-linked material demonstrated improved surface smoothness compared to the parent poly(terthiophene), which facilitated the synthesis of multicomponent nanoscale rods synthesized by the electrochemical deposition of gold, silver, and cross-linked polymer into the pores of anodized aluminum oxide templates. Importantly, it is found that inclusion of the poly(norbornene) backbone has no negative effect on either the fluorescence or the electrochemical properties of the poly(terthiophene). Rigid small-molecule DNA hybrids (rSMDH3's); where three DNA strands are attached to a rigid tris(phenylacetylene) core through benzyl phosphate bonds, and flexible SMDHs (fSMDHs) with alternating poly(ethylene glycol) spacers between three DNA strands were also synthesized. Dimers of rSMDH3:rSMDH3 possessing three parallel duplexes exhibited both an increase in melting temperature (by 12 °C) and a sharp melting transition (full width at half max of the derivative curve, FWHM = 2.5 °C), while double-clips of fSMDH materials with two closely bound duplexes only showed a 5 °C increase in melting temperature. Notably, these well-defined DNA hybrid systems reveal important roles that local geometry and ion concentration play in DNA hybridization/dehybridization processes and point the way for designing new DNA-based materials with enhanced recognition properties. Merging the signaling properties of the terthiophene materials with the recognition properties of the DNA hybrid materials allowed for the development of a "loaded" probe for amplified DNA diagnostics. Polymer nanoparticles (PNPs) assembled from amphiphilic block copolymers containing terthiophene groups were functionalized with DNA to create a PNP-DNA hybrid material which was implemented as a probe in a DNA detection assay. In comparison to the free polymer-based probe, the PNP-based probe gave signals that are amplified by at least two orders of magnitude.

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