Planar (Bio)Sensors for Critical Care Diagnostics

Advances in planar (bio)sensors have allowed whole-blood diagnostics to be applied in testing close to the patient, resulting in rapid turnaround times, which are especially desirable in critical care settings. Several new technologies and custom chemicals had to be integrated to allow high performance, small sample size, fast response time, and cost-effective devices. (Bio)sensors described below are used for measurement of blood gases, blood electrolytes, glucose, and lactate in point-of-care environments. Manufacturing of planar thick-film electrodes on ceramic wafers is now done with standard processes yielding precise patterns through the use of ultrapure metals for prolonged use-life under constant polarization. A platinized carbon paste ink has been developed to screen-print the active electrode of the glucose and lactate biosensor (Fig. 1 , top). In the amperometric sensor for Po2, Nafion (polymeric perfluorinated ionomer; Aldrich) is used as an internal electrolyte and is spin-coated with a custom-made, patented polymer (1). This polymer has a relatively low permeability for oxygen but is permeable to water vapor to allow fast wetting and a stable steady-state response signal (Fig. 1 , middle).