Research Of New Electrochemical DNA Biosensors Based On Single-walled Carbon Nanotubes

One-dimensional carbon nanotubes (CNTS) exhibit excellent electricconductivity, thermal stability, mechanical flexibility and high reactivity andhave thus attracted increasing attention from scientists. CNTs have beenwidely utilized in sensing, catalysis, energy storage and conversion,fabrication of composite materials, to name a few. This project aims tousing single-walled carbon nanotubes (SWCNT) array as the electrodesubstrate, combined with the great signal amplification exhibited by Aunanoparticles, to construct a simple, highly sensitive and selective detectionplatform, which is capable of quickly detecting trace amounts of DNAs. Themain contents of this research include:(1) Using Fe/Mo as catalyst and methane as the carbon source,horizontally aligned SWCNT array was produced on SiO2/Si wafers by thechemical vapor deposition method. It was followed by electrochemicaldeposition of gold nanoparticles on the as-prepared SWCNT array to buildSWCNTs/Au electrode. The morphology, chemical composition andelectrochemical properties of the electrode were characterized by scanningelectron microscopy, X-ray energy dispersive spectroscopy andelectrochemical impedance spectroscopy.(2) The DNA sensor was constructed via functionalizing theSWCNT/Au electrode with desired probe DNA molecules throughself-assembly approach. Electrochemical impedance measurements showthat the new sensor, in which every gold-coated SWCNT acts as anisolated micro electrode, could detect lower than10zmol complimentary10-base DNA, which corresponded to having6DNA molecules in a1mLsample solution. For a1-base mismatched DNA, the experimental detectionlimit is100amol. A linear relationship between the change of charge transfer resistance and target DNA concentration was achieved at lowconcentration range. Over the extended DNA concentration range, thechange of charge transfer resistance was found to have a linear relationshipwith respect to the logarithm of the target DNA concentration (Rct=4.58log[target-DNA]+63.04(R=0.998)). The sensor also showed great stabilityand could be conveniently regenerated via dehybridization in hot water.(3) The as-prepared SWCNT/Au platform was also explored as otherbiomolecule sensors, where thiol modified hepatitis B virus (HBV) andhuman papillomatosis (HPV) DNA were employed as the probe molecules.The produced SWCNTs/Au/HBV-ssDNA and SWCNTs/Au/HPV-ssDNAsensor electrodes were able to detect the related biomolecules at aconcentration as low as10-18M, which corresponds to having approximately600molecules in1mL hybridization solution. The functionalized electrodecould detect lower than1.0×10-13M of1-base mismatched molecules. Withinthe achieved linear concentration range, SWCNT/Au/HBV electrode yields△Rct=1.79log[target-DNA]+33.2，whereas SWCNT/Au/HPV electrode has△Rct=4.32log[M-DNA]+89.8with a linear correlation coefficient of0.990...