| Aptamer have become highly promising recognition probes due to convenient automated-synthesis, high stability, insensitivity to temperature, ease of saving. Proteins as one of the six basic nutrients in the human body play an important role in life activities. Quantitative analysis is a basic study about protein. It is significant to analysis of protein structure and function, diagnosis disease, medicine or genetically modified products and clinical sample. As development of scientific technology, currently biological sensor can not match higher requirement of protein detection. Therefore, many scientist make a great effort to develop a biological sensor with many advantages such as high sensitivity, less time consuming, high accuracy, easy-to-use and so on. The electrochemical methods have many advantages compared with the traditional optical method, such as rapid response, inexpensive, high sensitive and so on. Electrochemistry is opening new horizons for application of aptamer biological sensor.Owing to good physical and chemical properties of quantum dots, portability of the screen-printed electrodes, excellent conduction properties of nanoparticles and graphene, we constructed many novel protein electrochemical biosensors. The main points of this thesis are summarized as follows:(1) Simple and sensitive aptasensor based on quantum dot-coated silica nanospheres and the gold screen-printed electrode. Cyclic voltammetry (CV) and electrochemical impedance spectrum (EIS) were applied to investigate the electrochemical properties of electrode surface. Compared with the bare screen-printed electrode (SPE) and the AuNPS/SPE, the intensity of current observably enhance. Compared with the quantum dots modified electrode and without the quantum dots modified electrode, the intensity of current further enhances. On the basis of these, the aptasensor showed a good precision and high sensitivity for thrombin detection. It also showed high stability and selectivity.(2) The design relied on the structrue-switching properities of aptamers upon binding to their target molecules and signal enhancement of nanotechnology. The change of the interfacial feature of the electrode was characterized by electrochemical impedance analysis with [Fe(CN)6]3-/4-as the redox probe. Both [Ru(NH3)6]3+as the signaling moiety and graphene as signaling enhancement ensure that thrombin could be detected. Under the optimum conditions, the sensor exhibited a linear dependence on the concentration of thrombin from2x10-8ng-mL-1to1×10-7ng-mL-1and a low detection limit of0.1x10-9ng-mL-1(signal/noise=3).The results illustrate that the sensor with high sensitivity and good selectivity can be used in the real sample detection. The results also show that the graphene play an important role to detect low concentration of thrombin.(3) Methylene Blue can be expected to strongly interact with the WCNTs to form a new kind of stable MB-WCNTs nanostructure. On basis of this, a label free sensor was fabricated successfully. Influence of various experimental parameters on thrombin sensing, including scan rate was also investigated. Under the optimum conditions, the sensor exhibited a linear dependence on the concentration of thrombin from1×10-9ng-mL-1to1×10-7ng-mL-1and a low detection limit of1.0×10-9ng-mL-1(signal/noise=3).The sensor also show high sensitivity, reproducibility and selectivity. Owing to unique material, ease-to-get and low detection limit have provided the new direction of development of sensor technology. |
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