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

Abstract

The complex diaquabis[ N-(2-pyridinylmethyl) benzamide-κ 2 N, O]-cadmium(II) dinitrate {[CdL 2(H 2O) 2](NO 3) 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 [CdL 2] 2+ and salmon sperm DNA. Results showed that [CdL 2] 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 [CdL 2] 2+ and salmon sperm DNA was calculated to be 2:1 and the binding constant was 25.56 L 1/2 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 [CdL 2] 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 (3 σ, n = 11).