AN INTEGRATED NEEDLE-TYPE BIOSENSOR FOR INTRAVASCULAR GLUCOSE AND LACTATE MONITORING

A needle-type integrated biosensor has been developed for simultaneous intravascular lactate and glucose monitoring. In order to miniaturize the whole sensor and incorporate it into a hypodermic needle, the wor king electrode of the glucose sensor was made by electrodeposition of platinum on the needle surface followed by the electropolymerization o f 1,3-phenylenediaminr as the inner layer to eliminate the interferenc e from oxidizable physiological substances and to stabilize the platin um particles. The working electrode of lactate sensor was made from pl atinum wire which was fixed in the needle hollow body. Enzymes (glucos e oxidase and lactate oxidase) were immobilized with glutaraldehyde as cross-linking reagent and dithiothreitol as the stabilizer. PVC coati ng was used as the external diffusion control membrane. Sensor perform ance was evaluated in vitro and the sensor shows a sensitivity of 10 n A/mM for lactate, and 7.5 nA/mM for glucose, and a linear I ang of up to 16 mM for lactate and 24 mM for glucose. Evaluation of the sensor r esponse in blood plasma showed similar sensitivity and linear range as observed in buffer solution. Both individual sensors reacted specific ally to lactate and glucose and no cross-reactivity of significance wa s observed. Sensors showed a mi ni mum change in their performance whe n stored in buffer solution at 4 degrees C for more than 3 months.