Hybridization biosensor using diaquabis[N-(2-pyridinylmethyl)benzamide-κ2N,O]-cadmium(II) dinitrate as a new electroactive indicator for detection of human hepatitis B virus DNA

The complex diaquabis[N-(2-pyridinylmethyl) benzamide-κ2 N,O]-cadmium(II) dinitrate {[CdL2(H2O)2](NO3)2, where L = N-(2-pyridinylmethyl) benzamide} was synthesized and characterized by X-ray diffraction analysis. Fluorescence spectroscopy and voltammetry were used to probe the interaction between [CdL2]2+ and salmon sperm DNA. Results showed that [CdL2]2+ had excellent electrochemical activity on glassy carbon electrode (GCE) and could intercalate into the double helix of double-stranded DNA (dsDNA). In 0.2 mol L−1 NaAc-HAc media (pH 7.02), the binding ratio between [CdL2]2+ and salmon sperm DNA was calculated to be 2:1 and the binding constant was 25.56 L1/2 mol−1/2. An electrochemical DNA biosensor for the detection of human hepatitis B virus (HBV) DNA fragment was developed. The biosensor relied on the covalent immobilization of the 21-mer single-stranded DNA (ssDNA) related to HBV gene on the modified glassy carbon electrode (GCE). Using [CdL2]2+ as novel electroactive indicator, the hybridization between the probe and its complementary ssDNA, as the target, was investigated by differential pulse voltammetry (DPV). Experiment with non-complementary oligonucleotides was carried out to assess the selectivity of the developed electrochemical DNA biosensor. The target HBV DNA could be quantified ranged from 1.01 × 10−8 to 1.62 × 10−6 mol L−1 with good linearity (γ = 0.9962). The detection limit was 7.19 × 10−9 mol L−1 (3σ, n = 11).