Development Of New Label-free Biosensor Based Metal Compound

Nanophase materials，the most promising material in the world，show superiorperformance due to their specific surface effect, small size effect, macroscopicquantum tunneling effect and quantum size effect, and its electrical, magnetic,optical and chemical properties compared to the conventional materials. Theinvolvement of nanomaterials for the development of sensors provides endlessimagination because nanostructure of the material can be widely applied in thesensitive molecules fixed, signal detection and amplification. Compared with thetraditional sensor, new sensor based on nano-materials has ultrahigh sensitivity andselectivity, at the same time the response speed of the sensor will be greatlyenhanced. This dissertation focuses on the novel label-free biosensor based onnano-metal compounds. The results were described as following:（1） Because of highconductivity and biocompatible nanostructure of bismuth titanate （Bi₂Ti₂O₇）, theelectrode has a better electron transfer activity. The effective surface area ofelectrode was increased due to the rough surface of Bi₂Ti₂O₇, resulting in theimprovement of the current response of this biosensor.（2）Chlororutheniumammonium can be fixed to the DNA chain by the way of exchanging chloride ions andoxygen ions of the nucleotide aptamer, which greatly enhances the fixation effect ofsignal molecule in the detection system, resulting in the improvement of the currentresponse for the determination of lysozyme.（3） The endonuclease biosensor shows ahigh-sensitivity for the detection of lead ions because of specific binding of RNAnucleotide chain with Pb²⁺. Details are presented in this thesis as foloows:1A novel electrochemical DNA biosensor based on bismuth titanatenanoparticlesA novel, simple and labeled-free DNA biosensor was prepared by immobilizingBi₂Ti₂O₇with good biocompatibility on the surface of glassy carbon electrode. Theelectrode exhibited good differential pulse voltammetry （DPV） response to thecomplementary DNA sequences in the presence of the indicator daunomycin. Theelectrode morphology was characterized by scanning electron microscopy （SEM） and X-ray Diffraction. The electrochemical characteristics of the modified electrode wereinvestigated by cyclic voltammetry, electrochemical impedance spectroscopy （EIS）and DPV. Because of high conductivity and biocompatible nanostructure of bismuthtitanate （Bi₂Ti₂O₇）, the electrode has a better electron transfer activity. The effectivesurface area of electrode was increased due to the rough surface of Bi₂Ti₂O₇,resulting in the improvement of the current response of this biosensor. Underoptimum conditions, the biosensor exhibited a fast amperometric response and highsensitivity for monitoring DNA. The current response of the sensor increased linearlywith the concentration of target analyte from1.0×10-5to1.0×10?10M with arelative coefficient of0.9952. The detection limit （3σ） is1.34×10?12M, indicatingthat this modified electrode has potential application in sensitive and selectivedetermination of DNA.2Label-free detection of lysozyme based on characteristics of chlorineruthenium ammoniumUsing the characteristics of chlorine ruthenium ammonium and specific bindingbetween lysozyme and corresponding aptamer we prepared an unmarked and newtype of lysozyme biosensor. Because DNA single-chain would combine with positivelycharged lysozyme （isoelectric point is11） in the neutral pH conditions, the shortnucleotide chains being complementary to the aptamer will be separated from thenucleotide aptamer, resulting in a reducing of the electrochemical signal. Theelectrode morphology and response characteristic was characterized by differentialpulse voltammetry （DPV） and electrochemical impedance. Under the optimizingexperimental conditions, the range of the sensor response for lysozyme was1.0×10^-51.0×10^-9 M M with a relative coefficient of0.9971. The detection limit （3σ）is1.98×10^-11 M, indicating that this modified electrode has potential application insensitive and selective determination of lysozyme.3Lead biosensor based on bismuth titanate, chlorine ruthenium ammoniumand endonucleaseAfter forming the specific binding of Pb²⁺ and idiosyncratic RNA nucleotidechain, some RNA bases disconnected at the RNA strand in the presence of Pb²⁺, and a signal reducing type sensor for the determination of Pb²⁺ can be prepared. Underoptimizing experimental conditions, the sensor displays a linear range from1.0×10^-61.0×10^-10 M of Pb²⁺, with a relative coefficient of0.9981. The detectionlimit （3σ） is8.541×10^-11 M, indicating that this modified electrode has potentialapplication in sensitive and selective determination of Pb²⁺.