An electrochemical DNA hybridization biosensor developed based on graphite screen-printed electrodes (GSPEs) modified with Fe3O4@SiO2/DABCO was used for detection of short-sequence DNA of prostate cancer gene by using two different methods including direct and indirect. The proposed sensor was prepared by immobilization of a 19-mer ssDNA probe on the modified GSPEs surface for detecting the hybridization between the probe and its complementary and non-complementary sequence of the prostate cancer gene as a target. The hybridization process was detected based on the differential pulse voltammetric signals of the guanine oxidation and the hemin reduction as an electrochemical indicator through direct and indirect methods, respectively. The selectivity of the biosensor was studied by the using of non-complementary oligonucleotide strands capable of distinguishing complementary and non-complementary DNA sequence of the prostate cancer gene. The peak current intensity of guanine oxidation and hemin reduction showed an enhancement by increasing the concentrations of complementary strands from 1.0 × 10–11 to 2.0 × 10–6 M and 7.5 × 10–12 to 2.0 × 10–6 M, respectively. The limits of detection, LOD (based on 3σ), were found as 8.0 × 10–12 M and 6.4 × 10–12 M for direct and indirect detection methods, respectively.
