Fabrication Of Electrochemical DNA Biosensors Based On Signal Amplified By Nanomaterials

Electrochemical DNA biosensor is an electrochemical DNA detection technology. As a result of this testing equipment with simplicity, low cost, high sensitivity, easy to use together with modern analytic technology. In some fields it has attracted much attention, such as environmental monitoring, clinical diagnosis and drug testing. The innovation of this paper is to fully utilize the unique characteristics of nano-materials and modern electrochemical technology to prepare several novel electrochemical DNA biosensors. This thesis includes four parts:Chapter I: Introduced the principle of electrochemical DNA biosensor, its research progress and application. Puting forward the idea of this paper.Chapter II: We report the fabrication of a sensitive electrochemical DNA impedance biosensor for the detection of sequence-specific target DNA. A single-stranded DNA probe with a NH₂ group at the end (H₂N–ssDNA) was then covalently immobilized on the surface of polymeric film at room temperature. The change of interfacial charge transfer resistance (RCT) was confirmed the DNA hybrid formation. The experiment result shows SWCNTs can significant amplify the impedance signal during the DNA hybridization detecting, and the DNA sensor has high sensitivity and high selectivity.Chapter III: We outline here the fabrication of a sensitive electrochemical DNA biosensor for the detection of sequence-specific target DNA. A single-stranded DNA probe with a thiol group at the end (HS-DNA) was covalently immobilized on the surface of the AuNPs through Au–S bond. Scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) were used to investigate the film assembly process. Detection of DNA was performed by measuring the decline of peak current of the methylene blue (MB) by differential pulse voltammetry (DPV). This DNA biosensor can detect the target DNA concentration in the range of 1.0×10^-13 to 1.0×10^-6 M, with a detection limit of 3.5×10^-14 M (S/N = 3). In addition, the DNA biosensor exhibits excellent selectivity for single-mismatched DNA detection.Chapter IV: We develop a sensitive electrochemical DNA biosensor based on gold nanoparticles/Co₃O₄ hexagonal nanosheets. Co₃O₄ hexagonal nanosheets were synthesized, and characterized by SEM and XRD. A single-stranded DNA probe with a thiol group at the end (HS-DNA) was covalently immobilized on the surface of the AuNPs through Au–S bond. Electrochemical impedance spectroscopy (EIS) was used to investigate the film assembly process. Detection of DNA was performed by measuring the decline of peak current of the methylene blue (MB) by differential pulse voltammetry (DPV).