The Key Technology Research On Reflectance Modulated Biosensor

Reflectance modulated biosensor is a label-free optical biosensor with advantages of high sensitivity, simple structure and low cost, and also some potential for high-throughput detection. In this paper, the key technologies of the reflectance modulated biosensor will be discussed, the main contents include:1. Si O₂ / Si structure transducer is used in this paper, since Si is an absorbing medium, firstly the laws of refraction and Fresnel formulas in the absorbing medium are deduced. On this basis, according to the structure of the transducer, a model of the absorbent substrate is established,and its reflectivity formula is derived.2. The simulation methods is used to select the operating point of reflectance modulated biosensor. Firstly, according to the reflectivity formula of the surface of the transducer, the influence on the reflectivity of the transducer of Si O₂ film thickness, the incident light wavelength, polarization state, incident angle and other parameters is discussed, the reflectance difference based on wavelength method is used to optimize the parameters above under the conditions of experiments, the operating point that makes the transducer reflectivity most sensitive to changes of Si O₂ film thickness is obtained. Secondly, the influence on the stability of parameters of the operating point to the performance of the reflectance modulated biosensor is discussed,the results shows that: the wavelength drift near the operating point of the incident wavelength and small changes in the incident angle make less impact to sensitivity; transducer structure design meets the test requirements.3. Biosensing experimental platform is built, firstly the structure of the transducer designed by the research group and the problems encountered in specific applications research are analysed, the specific structure transducer is designed and produced on this basis.Secondly,the power stability, light beam uniformity of the light source of biosensing experiments are analyzed, tested and evaluated, the results shows that: a light source power fluctuation range is less than 0.6%, the uniformity of the beam fluctuation is about 1%, the light source meets the experiment claim. Finally, biological sensing experiments study is conducted, including system calibration experiment, the sensing unit self-assembled modified film, protein fixed experiment and rabbit anti-human Ig G concentration gradient experiments.The CCD camera is used to collect the image of the transducer surface when the incident light are red and green, the change of reflectance of the sensing unit is obtained by the data processing. The results show that:when the incident light are 524 nm green and 633 nm red, the change of reflectivity caused by the increasing of the film thickness is conformed to the theoretical analysis.The background noise of the transducer is suppressed after the biosensor experiments activation treatment, achieving the desired effect. In the rabbit anti-human Ig G concentration gradient experiments, the curve of detection signal intensity vs solution concentration of 633 nm red, 524 nm green and two reflectivity differential is consistent with the trend of the theoretical curve.Sensitivity obtained by wavelength reflectance method has an increase of 1.1 times and 0.8 times compared with the use of red light and green light.