Electrocatalytic oxidation of glucose on bronze for monitoring of saliva glucose using a smart toothbrush

Bronze is one of copper alloy materials that have been widely used not only in the Bronze Age, but also nowadays because they are hard, easy to cast and resistant against corrosion. For bronze, tin is commonly used as the major non-copper ingredient of bronze because of many highly desirable characteristics including the fact that metallic tin is not toxic. We find that the tin bronze is a suitable electrode material for non-enzymatic electrochemical glucose sensing in saliva. For electrocatalytic oxidation of glucose on the bronze electrode, a negative potential is applied for proton reduction which creates a temporary alkaline condition. The sensor has a linear range from 0 to 320 mu M with the regression equation: i = 11 + 0.015 C (i is the current in mu A and C is the concentration in mu M) with a correlation coefficient of 0.994. The sensitivity is found to be 480 mu A mM(-1) cm(-2), and the detection limit is 6.6 mu M with a signal-to-noise ratio of 3. The electrode is found to be highly selective towards glucose oxidation in the presence of interfering species such as ascorbic acid and uric acid. The electrochemical senor is integrated into a smart toothbrush for monitoring of saliva glucose, which is potentially useful for non-invasive screening of diabetes. Compared with other electrochemical glucose sensors, a naked bronze electrode is used as the working electrode to ensure the robustness of the sensor. No additional reagent is involved for the electrochemical determination of saliva glucose and the electrode can be regenerated simply by mechanically polishing for long-term uses.