Reaserch And Application Of Electrochemical DNA Sensor Based On Graphene

Electrochemical DNA sensor has been used in many fields such as environmentalprotection, medical diagnosis, biological engineering and so on. By combining theelectrochemical biosensing and biological gene amplification techniques, a newmethod for the detection of the endogenous gene sequences from microorganisms canbe build. Nanomaterials have great potentials in the design and application ofbiosensors because of its excellent biological compatibility and electrochemicalproperties. Application of nanomaterials for the immobilization of DNA probe hasbecome to a popular research topic. This thesis includes the following parts:(1) A nanocomposite composed of electrodeposited zirconia (ZrO2) and graphene(GR) was synthesized on the surface of carbon ionic liquid electrode (CILE). ThessDNA probe sequences were electrostatic adsorbed on the surface of ZrO2/GR/CILEto get the DNA sensor, which could hybridize with the target ssDNA sequence.Differential pulse voltammetric (DPV) responses of the electrochemical indicatormethylene blue (MB) on different DNA modified electrode were recorded to monitorthe hybridization reaction. The polymerase chain reaction (PCR) products ofstaphylococcus aureus gene sequences were successfully detected by the proposedmethod.(2) A carbon nano tube (CNT), GR and chitosan (CTS) composite was prepared,which was cast on the surface of CILE to get the modified electrode, which werecharacterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV).The single stranded DNA (ssDNA) probe sequence was electrostatic adsorbed on theCTS membrane to get the electrochemical DNA sensor, and further hybridized with thetarget ssDNA. MB was adopted as the electrochemical indicator, and DPV responsesof MB were recorded to monitor the hybridization reaction. The PCR products of bacillus cereus gene sequences were successfully detected by the proposed method.(3) GR and nanosized nickel oxide (NiO) were electrodeposited on the CILEsurface step-by-step to get the composite modified electrode. The probe ssDNAsequences were immobilized on the modified electrode surface through the interactionof ssDNA with nanosized NiO. After hybridization with target ssDNA sequence, DPVresponses of MB on different DNA modified electrode were recorded for monitoringthe hybridization reaction. This electrochemical DNA sensor exhibited gooddiscrimination ability to the one-base and three-base mismatched ssDNA sequences,and the PCR amplification products of salmonella enteritidis gene sequence weredetected with satisfactory results.(4) A mixture of ordered mesoporous carbon (CMK) and CTS were prepared andcast on the surface of CILE. The modified electrodes were characterized by SEM andCV. The ssDNA probe sequences were electrostatic adsorbed on the electrode surfaceto make the DNA sensor, which could be hybridized with the target sequences. DPVresponses of the electrochemical indicator MB on different DNA modified electrodewere recorded to monitor the hybridization reaction. The sensor was further used forthe detection of PCR products of corn endogenous gene samples with satisfactoryresults.In summary, four kinds of electrochemical DNA sensors were constructed in thisthesis, which were applied to detect specific sequences with high sensitivity, goodselectivity, and wider linear range. The proposed electrochemical DNA sensors had theability to distinguish the complementary, mismatched and non-complementary thessDNAsequence.