Electrochemical Deoxyribonucleic Acid Biosensor Based on Multiwalled Carbon Nanotubes/Ag-TiO2 Composite Film for Label-Free Phosphinothricin Acetyltransferase Gene Detection by Electrochemical Impedance Spectroscopy

A highly sensitive electrochemical deoxyribonucleic acid (DNA) biosensor based on multiwalled carbon nanotubes (MWNT)/Ag-TiO2 composite film was developed. The solution containing Ag-TiO2-MWNT composite was cast on the carbon paste electrode surface to form a robust film, which combined the advantages of the good biocompatibility of Ag-TiO2 composite and the fine conductivity, as well as the large active surface area of carbon nanotubes. The composite could greatly improve the immobilization capacity of the probe DNA. The morphologies and electrochemistry of the nanocomposite film were investigated by scanning electron microscopy and electrochemical techniques including electrochemical impedance spectroscopy and cyclic voltammetry, respectively. DNA hybridization events were monitored by a label-free method of electrochemical impedance spectroscopy. This label-free electrochemical impedance DNA biosensor showed high sensitivity and selectivity for phosphinothricin acetyltransferase gene sequence assay. The multicomponents films also displayed a high stability during repeated regeneration and hybridization process.