Theoretical Analysis And Elementary Experiment Of Bio-CD Sensor

Biology Compact Disc Sensor (BioCD Sensor) is a kind of label-freed biosensor. Based on the reading technique of Dig-CD system, it owes the characteristics of high-throughput, high-sensitivity and high-efficiency which has great application in the fields of environment protecting, food monitoring and clinical medicine. Two basic kinds of the BioCD sensor (Phase-modulation and Intensity-modulation) are deeply analyzed on the aspects of theory and experiment supported by National Science Foundation.Firstly, basic sensing principle of these two BioCD sensors is presented and new structures of discs are designed. Then according to the scalar diffraction theory, the theoretical model of BioCD sensor is built. The output power of scanning signals is simulated by Matlab and the effects of correlative parameters on system sensitivity are analyzed. Through the comparison of these two kinds of BioCD sensors, the conclusion is drawed that Phase-modulation BioCD sensor has the higher sensitivity while Intensity-modulation one has the simpler optical structure and preprocessing of detection.The directional immoblization of biorecognizers on the sensing cell is the key step in the biological molecule detection that would determine detection sensitivity. So the method of covalent binding is studied by experiment in this paper. Fluorescence image shows that the biorecognizer (human IgG) immobilized on the surface of SiO₂ could combine specificly with analyte (rabbit anti-human IgG).Lastly, Experimental study of BioCD sensor is carried out on the platform built by ourselves. Meanwhile the linearity of the platform is verified by a set of Phase-modulation checking discs made by Reactive Ion Etching (RIE). The outcome indicates that minimal output power P_min would response linearly for height changes of sensing cells which accords with theoretical conclusions. Then qualitative detection of the molecule (rabbit anti-human IgG) is conducted through Intensity-modulation discs fabricated by magnetron sputtering. It comes out that the amplitude of signals would be evidently shifted under the condition of biofilm thickness changing.