Research On Electrochemical Biosensor Based On Nanocomposits

Electrochemical immunoassay technology due to its high detection sensitivity, excellent selectivity, simple operation, the advantages of low cost and easy to miniaturization, has been applied to many areas such as clinical diagnosis, drug analysis, environment monitoring. Because of the development of nanotechnology, nanomaterials have been used in the electrochemical analysis. With gradual developing of the analysis method, improving the detection sensitivity is becoming one of the particular concern issues in analytical chemistry. The heated electrode can improve the sensitivity of electrochemical detection, besides the heating step wouldn’t impact the current intensity of electrochemical detection. It has been proved in the both theoretical and practical. Under the background of the current research, this paper is committed to develop some new type biosensors. These new biosensors contained some new biomarkers. Also the heated electrode is used to improve the sensitivity of the biosensors. This thesis involved nanometerials, electrochemical analysis technology, biological technology organically. It focuses on the application of electrochemical bioassay research. The main contents are as follows:1. Based on the heated electrode technology of MMP-9and IL-6two-component protein electrochemical immunoassayA new immunosensor of metal matrix protein-9(MMP9) and albumin (IL-6) protein has been build. It can realize simultaneous multi-element analysis in electrochemical method. The polystyrene@polydopamine-metal microspheres (PS@PDA-metal) is synthesized as biomarkers. The graphene nanoribbons is used to modify the heated screen printing electrode (HSPCE) material. Graphene nanoribbons can enhance the conductivity of the HSPCE. It also can support proteins because of its hydrophilic and low toxicity. The PS@PDA-metal labeled antibody can generate a strong current intensity in acetic acid buffer. The MMP-9and IL-6are fixed on the electrode to construct the sandwich type immune probe. The mutual interference between two reaction regions of the HSPCE can be ignored. The detection range of the immune probe is10-5～103ng mL-1. The detection limits are5fg mL-1to MMP-9and0.1pg mL-1to IL-6. The ratio of signal-to-noise ratio is3(S/N=3). This new designed method of protein detection can expand the test concentration range, reduce the detection limit. It has a good stability and reproducibility. For the actual sample testing, it also got the expected results. So the method can be used to detect proteins in clinical detection.2. Based on the titanium phosphate nanocomposite signal probe electrochemical bioassay of microRNA-21Titanium phosphate nanoparticles is synthesized. The cadmium ion enter into thepore of the TiP through ionic-exchange way. It is absorbed by electrostatic adsorption in the pore of nanoparticles. The activated nanoparticles linked up with the streptavidin. Then it can be used as a biomarker. Synthesis of gold nanoparticles load PEI/graphene which is modified to glassy carbon electrode. The modified electrode can fixed biosensor through Au-S bond. Using biotin avidin-response, the titanium phosphate biomarkers is linked up with the modified electrodes. A new kind of RNA biosensor has been build. The bioprobe was detected by anodic stripping voltammetry. The self-assembly process was characterized by using electrochemical impedance (EIS). The electrochemical detection was expressed by observing the cadmium ion stripping voltammetric peak, In this study a stripping voltammetry was used; a sandwich type of RNA hybridization probes was constructed. The detection range of the microRNA-21immune probe is10-10～10-18mol L-1; the detection limit is10-19mol L-1and the signal-to-noise ratio is3(S/N=3). This design method has a expand the test concentration range, the lower detection limit. It also has a good stability and repeatability. This biosensor has the potential in clinical detection of microRNA-21.