Functionalized conjugated polymers for signal amplifying biosensors and sensor arrays

Conjugated polymers (CPs) are great alternatives to the conventional fluorescence dyes as signaling reporters in biosensor design due to the fluorescent signal amplification property of CPs. Two series of CPs, poly(p-phenyleneethynylene) (PPE) and poly(p-oxadiazole-co-phenylene) (POX) derivatives, have been systematically designed, developed, and studied in this thesis to devise highly sensitive and selective novel molecular biosensors and sensor arrays for the detection of clinically important biological molecules. The key concept developed in the thesis work was the molecular design principles to combine biological receptor molecules for specific detection of target oligonucleotides and CPs as the signal transduction and amplification unit. To achieve this goal, a series of completely water-soluble and highly emissive conjugated polyelectrolytes (CPEs) were first developed through systematic investigation on the correlation between the polymer structure and its water-solubility. We also developed a method to bioconjugate CPEs to peptides and DNA by end-modification of the CPEs with a carboxylic acid group to develop hybrid bio/-synthetic sensory CPs and to achieve selective detection of target with amplified fluorescence signal in aqueous solution. DNA detection results using the CPE-DNA hybrid system confirmed large signal amplification by means of efficient Forster energy transfer from the energy harvesting CPEs to the fluorescent dye attached to the complementary analyte DNA. To apply the signal amplification scheme to practically more useful solid-state microarray novel conjugated polymers, POXs, having unique photochemical stabilities were developed. By applying on-chip DNA synthesis on the POXs and achieving efficient Forster energy transfer from POXs to the dye-labeled target DNA we successfully developed signal amplifying DNA microarrays. The signal amplifying scheme was combined with a self-signaling concept by means of introducing intercalating dyes and molecular beacon into the CPs for label-free detection. As a result of sensitive and selective prostate specific antigen detection has been demonstrated. In addition to the biosensor development, the developed bioconjugation technique between biological molecules and CPEs was uniquely applied to the development of CPE-antibody for live cell imaging. Selective live cell imaging of human B-cell lymphoma and human T-cell leukemia having largely enhanced sensitivity and excellent selectivity was demonstrated by using the CPE-antibody.