Adsorption and electrooxidation of nucleic acids at carbon nanotubes paste electrodes

Abstract

Carbon nanotubes paste electrodes (CNTPE) are shown to be suitable for adsorptive stripping potentiometric measurements of trace levels of nucleic acids. The influence of surface pretreatments, paste composition, nature of the nucleic acid, and accumulation conditions on the adsorption and further electrooxidation of different oligonucleotides and polynucleotides at CNTPE is described. The electroactivity inherent to carbon nanotubes has allowed us to obtain a large enhancement of the guanine oxidation signal compared to that obtained at its analogue carbon (graphite) paste electrode (CPE). Trace (μg/l) levels of the oligonucleotides and polynucleotides can be readily detected following short accumulation periods with detection limits of 2.0 μg/l for a 21 bases oligonucleotide and 170 μg/l for calf thymus dsDNA. The interaction between nucleic acids and CNTPE demonstrated to be mainly hydrophobic. The confined DNA layers demonstrated to be stable in air, in 0.200 M acetate buffer pH 5.00 and in 0.020 M phosphate buffer pH 7.40 + 0.50 M NaCl.