High Sensitive Ion-Channel Sensors for Detection of Oligonucleotides Using PNA Modified Gold Electrodes

Abstract

The gold electrodes modified with self-assembled monolayers composed of the peptide nucleic acid (PNA) probe and 8-amino-1-octanethiol were used for the detection of a complementary oligonucleotide with a detection limit of 5.1×10−10 M and a relative standard deviation of 1.5% in a pH 7.0 phosphate buffer solution. In contrast, no responses to a non-complementary oligonucleotide were observed. The electrode surface was positively charged in the phosphate buffer solution due to the protonated amine group of the thiol, where the electron transfer reaction between the electroactive marker [Ru(NH3)6]3+ and the electrode was hindered because of the electrostatic repulsion between them. Binding of the complementary oligonucleotide to the PNA probe monolayer cancels the positive charge at the electrode surface, and provides an excess negative charge at the surface, thereby facilitating the access of [Ru(NH3)6]3+ to the electrode surface and its redox reaction. This allows the indirect detection of the complementary oligonucleotide.