Study Of The Nanoparticles-Modified Electrochemical Biosensor

Nanoparticles have caught more and more attention because of their small sizes, large specific surface and good biological compatibility characteristics. Combined with nanophase materials, the electrochemical biosensor system, the sensitivity and reoccurrence property of the electrochemical biosensor could be greatly improved. Based on their unique physical and electrochemical properties, two kinds of electrochemical biosensors with high performance fabricated by using nanophase materials were achieved. The major contents of the thesis are as follows:1. A novel hemoglobin (Hb) biosensor based on the remarkable synergistic effects of cerium dioxide (CeO2) and multi-walled carbon nanotubes (MWNTs) for detection of hydrogen peroxide (H2O2) is presented. The Hb/CeO2/MWNTs/CHIT nanocomposite was nanoengineered by selected matched material components and optimized composition ratio to produce a superior H2O2 sensor. The preparation method is quite simple and practical. This composite matrix combined the advantages of MWNTs, CeO2 nanoparticles and chitosan (CHIT), with good electron transfer ability, attractive biocompatibility and fine film-forming ability, which could increase Hb attachment quantity and H2O2 detection sensitivity. In the optimum pH 7.0 phosphate buffer, the electrocatalytic response exhibited a linear dependence on H2O2 concentration in a wide range from 5.0×10-6 to 4.6×10-4 mol/L with a detection limit of 6.5×10-7 mol/L (3σ).2. In the present study, an electrochemical aptasensor for highly sensitive detection of thrombin was developed based on bio-barcode amplification assay. For this proposed aptasensor, aptamerI as the capture DNA was immobilized on the Au electrode. The functional Au nanoparticles (DNA-AuNPs) are loaded with barcode binding DNA and the target binding (aptamerII) by treating AuNPs with a solution containing the two alkyl-thiol capped oligonucleotides at a 90:1 ratio. Through the specific recognition for thrombin, a sandwich format of Au-aptamerI/thrombin/DNA-AuNPs was fabricated. After hybridization with the PbSNPs-labeled barcode DNA, bio-bar code comprised of aptamerII, barcode binding DNA, barcode DNA and AuNPs was obtained. Since a single Au nanoparticle could be loaded with hundreds of barcode binding DNA, each barcode binding DNA could further hybridize with the barcode DNA, so the amount of PbSNPs could be amplified on per sandwich format. The concentration of thrombin was monitored based on the concentration of lead ions dissolved from the bio-barcode. A preconcentration process of lead ions through differential pulse anodic stripping voltammetric (DPASV) technology further increased the sensor performance. As a result of these two combined effects, this aptasensor could detect as low as 6.2×10-15 mol/L thrombin. In addition, the sensor exhibited excellent selectivity against other proteins.