A CONDUCTING SALT-BASED AMPEROMETRIC BIOSENSOR FOR MEASUREMENT OF EXTRACELLULAR LACTATE ACCUMULATION IN ISCHEMIC MYOCARDIUM

In this paper, fabrication, characterization, and physiological applic ation of a miniaturized amperometric lactate biosensor are described. The sensor is based on cross-linked lactate oxidase and tetrathiafulva lene-tetracyanoquinodimethane (TTF-TCNQ) charge transfer complex. The sensor was developed for continuous quantitative measurement of the la ctate accumulation in ischemic myocardium under severe depletion of ox ygen. The sensor was evaluated in vitro at an applied potential of 0.1 5 V vs Ag/AgCl; it proved to combine all the performance characteristi cs desired for the present application, such as proper response in abs ence of oxygen, good operational stability, good accuracy and precisio n (103.5 +/- 1.2%), adequate response time (t(95%) = 80 s), and wide l inear dynamic range up to 27 mM (r = 0.9998) in N-2-saturated solution s and at 37 degrees C. The prepared sensors (n = 12) showed sensitivit y of 380 +/- 90 nA/mM, and a background current of 240 +/- 50 nA. The lower limit of detection is 0.4 +/- 0.15 mM with a S/N ratio equal to 3. Results obtained for direct lactate monitoring in ischemic rabbit p apillary muscle under no-flow conditions and PO2 <6 mm Hg are presente d.