The Electrochemical DNA Sensor Based On Electropolymerized Films And Application Of Nano Materials

The immobilization of ssDNA at the electrode is the key step in the preparation ofDNA biosensors. Many methods have been employed for the immobilization of DNA,including adsorption, self-assembly monolayer, covalent binding, blending andelectropolymerization. This paper focuses on fabricating novel electrochemical DNAbiosensors by use of polymerized films and nanoparticle. And the sequence-specificrelated to the PAT gene fragment was determined using this electrochemical sensor.The paper can be summarized as follows:1. Poly(2,6-pyridinedicarboxylic acid) (PDC) modified glassy carbon electrode (GCE)was prepared by potential scan electropolymerization in an aqueous solution. Mg²⁺ions were incorporated by immersion of the modified electrode in 0.5 mol/L aqueoussolution of MgCl₂ to complete the preparation of a genetic "activated" electrode readyfor binding the probe DNA. The ssDNA was linked to the conducting polymer byforming a bidentate complex between the carboxyl groups on the polymer and thephosphate groups of DNA via Mg²⁺. DNA immobilization and hybridization werecharacterized with differential pulse voltammetry (DPV) by using methylene blue (MB)as indicator and electrochemical impedance spectroscopy (EIS). The EIS was of highersensitivity for DNA detection as compared to voltammetric methods in our strategy.The DNA electrochemical biosensor was applied to determine the specific sequencerelated to the target PAT gene with the dynamic range comprised between 1.0×10^-9mol/L and 1.0×10^-5mol/L. A detection limit of 3.43×10¹⁰mol/L of oligonucleotideswas estimated. 2. The gold nanoparticles (NG) were modified on the PDC/GCE to prepareNG/PDC/GCE, and then ssDNA was immobilized on the NG/PDC/GCE by theinteraction of NG to DNA. The NG modified on the PDC enhanced dramatically theimmobilization amount of the DNA probe, and improved greatly the sensitivity ofDNA detection. The sequence-specific related to the PAT gene fragment wasdetermined using this electrochemical sensor with a detection range from 1.0×10¹⁰mol/L to 1.0×10^-5 mol/L and a detection limit of 2.41×10^-11 mol/L.3. DNA probes with phosphate group at the 5' end were easily immobilized on thezirconia thin films due to the strong affinity between zirconia and phosphoric group.The DNA electrochemical biosensor was described for electrochemical impedancespectroscopy detection of the sequence-specific related to PAT transgene in thetransgenic plants. The dynamic detection range was from 1.0×10^-11 mol/L to 1.0×10^-6mol/L and the detection limit was 1.38×10^-12 mol/L.