A DNA electrochemical sensor with poly-l-lysine/single-walled carbon nanotubes films and its application for the highly sensitive EIS detection of PAT gene fragment and PCR amplification of NOS gene

A sensitive and novel DNA electrochemical biosensor for the detection of the transgenic plants gene fragment by electrochemical impedance spectroscopy (EIS) was presented. The well-dispersed carboxylic group-functionalized single-walled carbon nanotubes (SWNTs) were dripped onto the carbon paste electrode (CPE) surface firstly, and poly-l-lysine films (pLys) were subsequently electropolymerized by cyclic voltammetry (CV) to prepare pLys/SWNTs/CPE. The morphology of pLys/SWNTs films was examined using a field emission scanning electron microscope (SEM). The pLys/SWNTs films modified electrode exhibited very good conductivity. DNA probes were easily immobilized on the poly-l-lysine films via electrostatic adsorption. The hybridization events were monitored with electrochemical impedance spectroscopy using [Fe(CN)₆]^3−/4− as indicator. The PAT gene fragment from phosphinothricin acetyltransferase gene was detected by this DNA electrochemical sensor. The dynamic detection range of this sensor to the PAT gene fragment was from 1.0 × 10⁻¹² to 1.0 × 10⁻⁷ mol/L. A detection limit of 3.1 × 10⁻¹³ mol/L could be estimated. The PCR amplification of NOS gene from the sample of a kind of transgenic modified bean was also detected satisfactorily by EIS.