Electrochemical Glucose Detection With Microfluidic Chip Cell

Diabetes mellitus, indicated by high glucose concentration in blood, is one of the major diseases that affect people's health. Daily monitoring of the glucose level is important not only in the diagnosis, but also in the process of theraphy. An ideal glucose biosensor should have many advantages such as high specific, fast, easy to use, low cost, and so on. Miniaturization and portability of the detection system are also highly demanded. The occurance of microfluidic technology offers a good opportunity for the development of small biosensor device with less sample and reagent consumption.The status of biosensors in general, and electrochemical glucose biosensors in particular are reviewed, and the main issues are analyzed. It is proposed that electrochemical detection of glucose conventionally by enzyme modified macro electrodes could be realized by interfacing a capillary enzyme micro-reactor and a microfluidic electrochemical chip cell.Flow glucose detection was established based on a microfluidic electrochemical chip cell developed in the lab. Immobilization of glucose oxidase in a piece of capillary as a micro reactor was firstly studied involving adsorption, covalent binding, sol-gel entrapment and cross-linking. And flow detection of glucose solution was achived by interfacing the capillary reactor and the chip cell. The Michaelis-Menten constant (Km) of enzyme was 15.24 mmol/L, and good linearity (R=0.9976) was obtained in the range of 0.5～10.0 mmol/L with a detection limits of 0.25 mmol/L(S/N=3) and a relative standard deviation (RSD) of 2.8%(n=9).Chitosan was introduced for improving the enzyme immobilization, and suppression effect of Cu2+, Pb2+, Cd2+ and Cr3+ to GOD was obviously alleviated. The Michaelis-Menten constant (Km) of enzyme was 10.94 mmol/L, and good linearity (R=0.9988) was obtained in the range of 0.5～10.0 mmol/L with a detection limits of 0.1 mmol/L (S/N=3) and a relative standard deviation (RSD) of 4.2%(n=9). Glucose in plasma sample was measured with high recovery in the range of 96～106%, and no significant difference (P=95%) was noticed comparing to a glucose instrument from the market.P-benzoquinone(p-BQ) was introduced as an electron mediator for lowering the electrochemical interference due to other electrochemically active species such as ascorbic acid. With 0.01 mol/L BQ, linear response (R=0.9982) was obtained in the range of 0.2～3.0 mmol/L with RSD of 4.1%(n=11). Recovery rate from plasma sample was between 96～102%. The same result (P=95%) as that of a commercial instrument was obtained for the plasma sample.The system introduced in this work is characterized in small size, continuous operation, small consumption of samples and high speed. With further optimization, this system could become a new type of glucose electrochemical detection system, and find applications in diagnosis, therapy and process monitoring.