Research On Bio-sensing Through Microwave Signals

In recent years,microwave detecting technology has received wide attention because of its non-contact,non-intrusion,non-pollution and rapid measurement characteristics.With its diverse application background,microwave detecting technology has been widely applied in inter-discipline research.Glucose oxidase is a kind of oxidoreductase that is extensively used in food and medical industries where the information of its activity is necessary before the use of enzyme.There are a variety of methods to detect the activity of glucose oxidase.However,each of them has advantages and disadvantages.The application of microwave detecting technology in enzyme activity testing can simplify the experimental operation,thus realizing a non-intrusive,continuous and intelligent detecting method.In this thesis,we use microwave detecting technology to detect the activity of glucose oxidase.Specifically,a microstrip line device and a cavity resonator are used to detect the electrical parameters such as resonant frequency,reflection coefficient(S₁₁)and transmission coefficient(S₂₁)of the reaction solution before and after an enzymatic reaction.Then these parameters are compared with the enzyme activity tested with the spectrophotometric method,thus confirming if microwave detecting technology can be used to detect the activity of glucose oxidase.The research and the results presented in this thesis include:1.A microstrip line device is used as biosensor to detect the reflection coefficient of the reaction solution before and after the enzymatic reaction.The results show that the microstrip line device can detect the change of the relative dielectric constant caused by the change of the contents in the solution,and that the reflection coefficient detected by a microstrip-line device changes with a same trend as the enzyme activity detected by the spectrophotometric method,that is,?S11 increases in the range of pH4.5 to pH5.5,but decreases in the range of pH5.5 to pH6.5.This confirms that the microstrip line can be used to detect the activity of glucose oxidase.2.The microstrip line device is used for real-time monitoring of glucose oxidase-catalyzed reaction.The results show that the reflection coefficient increases with the increase of reaction time in the frequency range from 5400 MHz to 5440MHz.This again confirms that a microstrip line device can be used in real-time monitoring of the glucose oxidase reaction.3.A cavity resonator is used as biosensor to detect the resonant frequency and transmission coefficient of the reaction solution before and after the enzymatic reaction.The results show that the resonant frequency of the reaction solution shifts after the enzymatic reaction and that the frequency shift detected by a cavity resonator changes as a same trend of the enzyme activity detected by the spectrophotometric method as well as that of the microstrip line.4.The cavity resonator is used for real-time monitoring of glucose oxidase-catalyzed reaction.The results show that the resonant frequency decreases with the increase of the reaction time in the frequency range from 12.60 GHz to 12.75 GHz.This confirms that a cavity resonator can be used in real-time monitoring of glucose oxidase reaction.