Detection of short oligonucleotide sequences using an electrochemical DNA hybridization biosensor

An electrochemical DNA hybridization biosensor was developed for the detection of DNA hybridization using MDB and proflavine as electrochemical labels. The biosensor was based on the interaction of 7-dimethyl-amino-1,2-benzophenoxazinium Meldola's Blue (MDB) and proflavine also, with double stranded DNA (dsDNA) The electrochemical behaviour of MDB and proflavine as well its interaction with double stranded (dsDNA) were investigated by cyclic (CV) and square wave voltammetry (SWV) and screen printed electrodes (SPE). Furthermore, DNA-hybridization biosensors were developed for the detection of hybridization between oligonucleotides, which was detected by studying changes in the voltammetric peaks of MDB (reduction peak at -0.251 V) and proflavine (reduction peak at 0.075 V). MDB and proflavine were found to intercalate between the base pairs of dsDNA and oligonucleotides. Several factors affecting the dsDNA or oligonucleotides immobilization, hybridization and indicator preconcentration and interaction time, were investigated. As a result of the interaction of MDB with dsDNA and hybridized oligonucleotides, the voltammetric signals of MDB increased. Furthermore, guanine's oxidation peak (at 0.901 V) was decreased as MDB's concentration was increased. Therefore, as a result of the interaction of proflavine with dsDNA and hybridized oligonucleotides, the voltammetric signals of proflavine decreased. These results were similar as concerned carbon paste and screen printed electrodes. A comparison of the performance between CPE and SPE was done. Our results showed that lower concentrations of MDB and proflavine were detected using screen printed electrodes. Moreover, reproducibility was better using screen printed electrodes and the detection was faster (regarding the experimental steps), but they are more cost effective.