A facile electrochemical method for simultaneous and on-line measurements of glucose and lactate in brain microdialysate with prussian blue as the electrocatalyst for reduction of hydrogen peroxide.

This study demonstrates a facile electrochemical method for simultaneous and selective on-line measurements of glucose and lactate in the brain of freely moving rats through integration of selective electrochemical detection with in vivo microdialysis. The selective electrochemical detection is accomplished by using oxidases as the specific sensing unit and prussian blue (PB) as the electrocatalyst for the reduction and thus for the determination of H(2)O(2) generated from the oxidase-catalyzed reactions in terms of its excellent electrocatalytic activity toward H(2)O(2) reduction. The uses of "artificial peroxidase" (i.e., PB) in this work to replace "natural peroxidase" (i.e., horseradish peroxidase) used in the previous on-line electrochemical methods essentially enables the method developed here to be facile but selective for the simultaneous and on-line measurements of glucose and lactate virtually interference-free from ascorbic acid and other electroactive species coexisting in the brain. Moreover, the dual oxidase/PB-based biosensors suffer from little cross-talk and exhibit a good stability and reproducibility. The basal levels of glucose and lactate in the microdialysate from the striatum of the freely moving rats are determined to be 200 +/- 30 and 400 +/- 50 microM (n = 3), respectively. The method demonstrated here is facile but reliable and durable and may find some interesting physiological and pathological applications.