Biosensors Based On Water-Soluble Polythiophene Optical Probes

Fluorescent probes based on conjugated polyelectrolytes(CPEs) have wideapplications in biosensors due to their signal amplification effects and goodbiocompatibility. Hitherto, most CPE-based biosensors have been applied tobiomacromolecules detection, whereas small biomolecules with simple structures havereceived few attention because the weak interactions between them and CPEs limitedthe sensitivity of their detection. Water-soluble poly(3-alkoxy-4-methylthiophene)s(P3RO-4MeT) with chain conformations sensitive to external stimuli, are among themost investigated CPEs due to the ease of synthesis and functionalization. They havebeen confirmed to be sensitive colorimetric and fluorescent probes for biosensors. Inthis dissertation, a series of water-soluble P3RO-4MeTs were synthesized and appliedto determine and distinguish several biological important small biomolecules. The maincontents and results are summarized as follows.A few water-soluble P3RO-4MeTs were synthesized and their performances forthe detection of small biomolecules were investigated. The results indicated that thesensing mechanism can be attributed to the analyte-induced aggregating/disaggregatingof polymer backbones, under the synergetic effects of electrostatic, hydrophobic andaromatic stacking interactions.1. Water-soluble P3RO-4MeT can be used as sensitiveand selective optical probes for the detection of folic acid and surfactants by adjustingthe hydrophilicity/hydrophobicity or the charge properties of P3RO-4MeT. Thisstrategy provided an important clue to improve the selectivity of the probes towardssmall biomolecules with similar structure.2. P3RO-4MeT can be applied to detectglutathione, cysteine, homocysteine and taurine by introducing aromatic moieties intothe analytes through an in situ premodification technique. This method will not onlyextend the scope of CPE-based biosensors but also provide a new strategy for the faciledetection of small biological thiols.3. Discriminating fifteen nucleotides along withmonophosphate and pyrophosphate with100%confidence limits was realized, using asingle cross-reactive probe PMTPA by the combination of color changes andwavelengths array method. This approach takes advantage of a single probe instead of asensor array and avoids the synthesis of differential receptors. The sensing mechanism which involves aggregating/disaggregating of polymericprobes was investigated systematically. It was found that the kinds of charged moietyand aromatic moiety, together with charge number of both analytes and probes, play keyroles in promoting the assembly and disassembly of the aggregates. Moreover, the vitalrole of the charged moieties was exploited in terms of the hard-soft acid-base theory.This conclusion can be applied to guide the design of probes for sensing smallbiomolecules.