A Nucleic Acid Biosensor Based on Catalyzed Formation of Polyaniline

An ultrasensitive nucleic acid biosensor is described in this work. Following hybridization with a complementary nucleic acid and horseradish peroxidase (HRP) labeled oligonucleotide detection probe, a mixture of aniline/H₂O₂ in 0.10 M pH 4.0 phosphate buffer was applied to the biosensor. The hybridized polyanionic nucleic acid molecules serve as templates and HRP is the catalyst (aniline polymerization initiator). As a result, polyaniline deposition occurs preferably at the nucleic acid molecules on the biosensor. Thus, the deposition of polyaniline confirms and amplifies the sensing process of the analyzed nucleic acid and the amount of the deposited polyaniline directly correlates to the amount of hybridized HRP labeled detection probe. Thus, nucleic acid molecules were quantified voltametrically at femtomolar levels.