Porous carbon composite/enzyme glucose microsensor

An enzyme glucose microsensor using a glucose oxidase-immobilized porous carbon/Teflon composite microelectrode was developed. The microsensor was fabricated by etching a platinum microelectrode (platinum, radius of 25 and 50 micrometers) in hot aqua regia to create a cavity at the tip and then packing a porous carbon/Teflon composite, which was made from acetylene black and Teflon emulsion, into the cavity. Nafion was impregnated into the inner surface of porous carbon/Teflon composite electrode following immobilization of Os(bpy)3+2/+3 as electron transfer mediators. The loading amount of Os(bpy)3+2/+3 in the Nafion/porous carbon/Teflon composite electrode was found to be 7.0x10(-8) mole cm(-2), which is much higher than that in polymer modified electrodes reported in literatures. The microsensor was further dipped overnight in buffer solution containing glucose oxidase for enzyme modification. With both glucose oxidase and mediators in the porous carbon/Teflon composite surface, the sensor performance was evaluated in buffer solutions containing different glucose concentrations and serum samples for glucose determination. The microsensor showed directly electrochemical glucose oxidation on the Os(bpy)3+2/+3 impregnated enzyme/porous carbon/Teflon composite surface with linear response over concentration range of 0-15 mM and Machaelis behavior. Reliability and reproducibility were conducted in serum samples and glucose buffer solution, and the results demonstrated there was no significant decrease of amperometric response in air-saturated solution for one month. The sensor demonstrated potential in clinical diagnostic applications.