Indicator-Free Electrochemical DNA Biosensor Based on Adenine and Guanine Signals

Abstract

A novel electrochemical hybridization biosensor protocol without using an external indicator is described. The oxidation signals of adenine and guanine from calf thymus double-stranded DNA (dsDNA) and calf thymus single-stranded DNA (ssDNA) was studied by using differential pulse voltammetry (DPV) at carbon paste electrode (CPE). The oxidation signals of adenine and guanine obtained from the ssDNA modified CPE was higher than that from the dsDNA modified CPE due to the accessible unbound adenine and guanine bases. The electrochemical determination of hybridization between native capture DNA probe and target oligonucleotides and polynucleotides such as poly[G], poly[C], poly[I] and poly[A], poly[T] were also accomplished. The dependence of the peak heights of guanine and adenine signals on the number of the respective bases in oligonucleotides was observed by means of DPV. The dependence of the guanine signal upon the concentration of the target and the noncomplementary DNA sequences was also observed. The use of the intrinsic DNA electrochemical signals for monitoring hybridization events offers several advantages over the common use of carcinogenic external indicators and expensive inosine substituted capture DNA probes, such as a shorter assay time and cost-effective procedure. Performance characteristics of the biosensor are described, along with future prospects.