CHEMICAL MICROSENSOR SYSTEMS FOR MEDICAL APPLICATIONS IN CATHETERS

For the analysis of chemical parameters in human blood, miniaturised sensors have been developed and implemented in common catheter systems. Based on the principle of amperometric sensors, enzyme chips for lactate and glucose determination have been constructed by depositing a thin-film noble metal electrode and a reference electrode at one side of the silicon chips. The enzymes are entrapped into poly-urethane films which are directly attached to the chip surface and optimised by chemical surface modification. The potentiometric sensors have silicon micromachined grooves containing ion-selective ionophores in modified poly(vinyl chloride) (PVC) and electrodes located on both sides of the silicon chip. By means of an intelligent analyte management system the exposure time of the sensors to serum or blood was reduced to about one min/hour. The sensors are conditioned and calibrated immediately before each blood measurement. The analyte and calibrant handling and the signal treatment are controlled by a microprocessor. The sensors assembled in the catheter tip respond reproducibly and accurately to the respective analytes in human serum for more than 70 h.