Investigations On Microcantilever Immunosensor Technique

Microcantilever biosensor is a new analysis method. Its research relates to the MEMS (microelectromechanical systems), Materials, Biochemistry, Mechanical and other cross-disciplinary subject. Microcantilever is a simplest device of MEMS. The mechanism is based on that a stress change generated from the biochemical binding events onto the gold surface will drive the microcantilever deflection, this characteristic make this method appealing for applications in biochemical sensing in the future.In this dissertation, as it is a key step to immbolize antigen / antibody molecules on the gold surface of microcantilever to achieve reproducibility and stability of immune sensing system, we focus on different immobilization methods for detection of small molecules, the analysis sample such as the natural anti-cancer drugs, heavy metals, pesticides and plant hormones, and detection sensitivity of different immobilization methods was compared. Lastly, two approaches for design of microcantilever array sensor were discussed. The main work of this dissertation is as follows:In the chapterⅠ, we summarize the development history of microcantilever sensing technology, work principle and research progress in the chemical, biological and nanotechnology were also review.In the chapterⅡ, the impact of quadrant detector system from property of the laser spot and sensitivity factors from the environment and background light were discussed, and the design of flow cell and the optimization of the liquid flow velocity were described. As the refractive index change impact on measured sensitivity, we design of a new portable liquid concentration detecting optical system. The concentration detection of sodium chloride solution sensitivity is 1‰.In the chapterⅢ, three immobilization methods on the gold surface of a microcantilever immunosensor were developed for label-free detection of the small molecule. The binding of the antibody on the gold surface of the microcantilever was evaluated by non-competitive Enzyme-Linked Immunosorbent Assay (ELISA). Glutathione S-transferase was modified on the gold surface of microcantilever by the thiol self-assembly, and its antibody was detected. The sulfhydrylated different antibodies were synthesized and immobilized on the gold surface of the microcantilever. Deflections of the microcantilever was detected corresponding to different antigen, such as the paclitaxel, copper ion, gibberellin and indole acetic acid, the detection sensitivity of the standard sample solution as: 0.8 ng / mL, 0.78 ng / mL, 4.5 ng / mL, 100 ng / mL, and detection of paclitaxel in plasma and copper ions in tap water;The sulfhydrylated second antibody immobilization method was used for detection of ethyl parathion with the detection sensitivity of 5 ng / mL, this method provided a new method detection of pesticide and provide a new method for the modification of the surface of antibodies on the gold surface of microcantilever; The thiol self-assembly, sulfhydrylated antibody and sulfhydrylated second antibody were modified on the gold surface for detection of molecules, while taking advantage of enzyme-linked immunosorbent assay methods and surface plasmon resonance of the gold surface antibody instrument repair effect, the results show that method of sulfhydrylated second antibody can provide more antigen binding site, so this immobilization method is superior to other methods of detection sensitivity.In the chapterⅣ, for multi-target detection, we established readout optical defocus path with the CCD for microcantilever bending. A new method provides an easy way to integrate and realize sensor function of two microcantilevers by the two laser diodes and the beam splitter prism, realizing the micro-adjustable distance for microcantilever array. Continue the experiment will focus on development readout for more microcantilevers.In the chapterⅤ, main content in this dissertation is summarized, and the application prospect in this field is discussed.