Thesis (Ph.D.)--Chulalongkorn University, 2009

In this work, DNA sensors have been developed based on pyrrolidinyl peptide nucleic acid (adpcPNA) and surface plasmon resonance (SPR). Twelve acpcPNA oligomers were synthesized. PNA1-7 functionalized with thiols were directly immobilized on the gold SPR disk by self-assembled monolayer (SAM) formation. The density and the stability of the immobilized PNAs, the immobilization condition, the effects of thiol modifiers and blocking thiol on DNA hybridization efficiency, the specificity of sensor and detection limit were determined. In addition, PNA8 functionalized with biotin was synthesized for indirect immobilization via biotin-streptavidin-biotin interaction. In this part, acpcPNA, DNA and commercial peptide nucleic acid (aegPNA) probes with the same base sequence were compared in terms of the effect of ionic strength on hybridization efficiency, the specificity, the direction of binding (parallel or antiparallel) to target DNAs, and the effect of target DNA concentration on hybridization efficiency. The results indicated that the indirect immobilization yielded the higher DNA hybridization efficiency than the direct immobilization, the acpcPNA probe was the best sensing probe in term of specificity, and the sensor can be reused for multiple cycles of DNA hybridization detection. Finally, the SPR technique was also applied for studying the formation of higher-order complexes between the unmodified PNA9-12 and surface-immobilized single or double-stranded DNA