AMPEROMETRIC MONITORING OF LACTATE ACCUMULATION IN RABBIT ISCHEMIC MYOCARDIUM

Fabrication and characterization of miniature, flexible, planar biosen sors for monitoring L-lactate accumulation in an ischemic myocardium a re described. Three configurations of Au-based electrodes were fabrica ted by a photolithographic technique on flexible polyimide Kapton(R) f oil. All sensors are based on an immobilized lactate oxidase with ampe rometric detection of the enzymatically produced hydrogen peroxide al a platinum-electroplated-gold base electrode polarized at 0.5 V versus Ag/AgCl. An inner electropolymeric layer is used to prevent electrode fouling and to reject the interference effects of easily oxidizable m olecules. In addition, a diffusion controlling outer layer that greatl y enhances the linear dynamic range of the sensor, is obtained by cast ing a polyurethane external film. The developed sensor was evaluated i n vitro and proved to have high selectivity, good operational stabilit y, good accuracy and precision (average recovery = 102.3 +/- 0.4% for control sera), fast response time (t(95) = 20 s) and high upper limit of the linear dynamic range (25-80 mM, with sensitivity of 1.7-0.4 nA mM(-1), respectively at PO2 = 15 mmHg). Subsequently, the sensor was b rought into direct contact with the surface of the rabbit papillary mu scle and used for continuous quantitative monitoring of extracellular lactate accumulation during no-flow ischemia. (C) 1997 Elsevier Scienc e B.V.