A high-sensitive electrochemical DNA biosensor based on a novel ZnAl/layered double hydroxide modified cobalt ferrite-graphene oxide nanocomposite electrophoretically deposited onto FTO substrate for electroanalytical studies of etoposide.

The combination of layered double hydroxides (LDHs), cobalt ferrite (CoFe2O4) and graphene oxide (GO) creates a ternary nanocomposite that can incredibly improve advantages of each compound; this is an impressive way to attain multifunctional materials with attractive properties. In this study, a new high-sensitive electrochemical DNA biosensor was fabricated for the electroanalytical studies of etoposide using a novel ZnAl/layered double hydroxide modified cobalt ferrite-graphene oxide nanocomposite (GO/CoFe2O4/ZnAl-LDH) that was electrophoretically deposited (EPD) on the fluorine tin oxide (FTO) substrate. This DNA biosensor was prepared via electrostatic adsorption of DNA onto the GO/CoFe2O4/ZnAl-LDH/FTO electrode. The electrochemical behavior of electrodes was characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). EIS plot obviously demonstrated a rapid electron transport at low frequencies for GO/CoFe2O4/ZnAl-LDH. Differential pulse voltammetry (DPV) and square wave anodic stripping voltammetry (SWASV) were employed for the electrochemical detection of ETO. The results revealed that DNA/GO/CoFe2O4/ZnAl-LDH/FTO bioelectrode had ultrahigh sensitivity to ETO with the detection limit of 0.0010 μM in the linear range of 0.2-10 μM. In addition, the developed biosensor revealed precise reproducibility and excellent stability of about 95% of the initial activity after 6-7 weeks. On the other hand, the present bioelectrode was also capable of discriminating different interferences and was also used to detect etoposide in real samples such as human blood plasma, serum and urine with good recoveries, ranging from 97.0% to 104.0%. The obtained results of the excellent performance of this biosensor could be assigned to the active reaction sites and good electrochemical activity of nanocomposites, hence helping increase the DNA immobilization and accelerate the electron transfer more effectively on the surface electrode.