Impedimetric genosensor for ultratrace detection of hepatitis B virus DNA in patient samples assisted by zeolites and MWCNT nano-composites

Nanocrystals of zeolites (Nanocrys Zeo) and Multi-walled carbon nanotubes (MWCNT) based diagnostic genosensor was employed for detection of polymerase chain (PCR) amplified HBVDNA in blood of hepatitis B patients. The ssDNA-nanocomposite modified electrode was characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The hybridization between ss DNA probe and target ss DNA was detected by reduction in current, generated by interaction of methylene blue (MB) with free guanine (3′G) of ssDNA. Nanocrys zeo were deposited on the Fluorine doped tin oxide glass electrode (FTO) by drop-casting method for better immobilization of ss DNA while MWCNTs are incorporated into the zeolite-assembly to enhance the electro-conductivity of the present genosensor. The ssDNA-nanocomposite modified FTO electrode exhibited optimum current within 5 s, at pH 5.6, and incubation temperature of 45 °C. The value of charge transfer resistance (Rct) was linear with the number of copies of target DNA between 150 and 106 copies/ml. The limit of detection (LOD) of the sensor was 50 copies/ml. Within and between batches coefficients of variation (CV) were 2.5% and 3.2% respectively. Results obtained with our genosensor were also correlated with those by RT-PCR and r2 value found with good accuracy of 97%. The electrode was reused by dipping it into 0.1 M NaOH for 3 min and lost 50% of its initial activity in 4 weeks. Furthermore the technique employed for detection of HBV is EIS, which is convenient and required less analysis time.