Reaserch And Application Of Electrochemical DNA Sensor Based On Nanomaterial Modified Carbon Ionic Liquid Electrode

More requirements about food quality and the detection of pathogenicmicroorganisms were brought forward by food safety. By combining the electrochemicalbiosensing and biological gene amplification techniques, a new method based on thedetection of the endogenous gene sequences from food or pathogenic microorganisms canbe proposed for the control of food safety. Nanomaterials have shown great potentials inthe design and application of biosensors because of its excellent electrochemicalproperties and biological compatibility. Application of nanomaterials used as basementfor DNA probe fixed has became to a popular research topic. The thesis can besummarized as follows:Co₃O₄nanorod and Fe₃O₄microsphere was mixed with graphene respectively, and thenanocomposites were casted on the surface of carbon ionic liquid electrode （CILE） toform a membrane by the help of chitosan. The modified electrodes were characterized byusing scanning electron microscope, cyclic voltammetry and electrochemical impedancespectroscopy. The single stranded DNA （ssDNA） probe sequence was electrostaticadsorbed by the chitosan membrane, and further hybridized with the target ssDNA.Methylene blue （MB） was adopted as the electrochemical indicator, and differential pulsevoltammetric responses of MB were recorded to monitor the hybridization reaction. Thepolymerase chain reaction products of endogenous gene sequences from staphylococcusaureus and soybean oil were successfully detected by the proposed method.The mercaptoacetic acid was assembled on electrodeposited gold nanoparticledecorated CILE and graphene/CILE surface by the specific binding ability betweenalkane thiol molecular and gold. Then amino modified ssDNA probe sequence was covalently-linked with mercaptoacetic acid to get the ssDNA modified electrode for thefurther hybridization. MB was used as the electrochemical indicator for monitoring thehybridization reaction. The polymerase chain reaction product of arachis and Listeriamonocytogenes endogenous gene sequences was successfully detected by the proposedmethod.In summary, four kinds of electrochemical DNA sensors were constructed in thisthesis, which can detect specific sequences with high sensitivity, good selectivity, and theability to distinguish the complementary, mismatched and non-complementary the ssDNAsequence.