ION-SELECTIVE MICROCHEMICAL SENSORS WITH REDUCED PRECONDITIONING TIME- MEMBRANE BIOSTABILITY STUDIES AND APPLICATIONS IN BLOOD ANALYSIS

Progress on solution of two general problems regarding the use of in v ivo planar microchemical sensors is reported. These are issues of shor t term and long term response stability. Reduction of preconditioning time (hydration period), i.e., the time needed by the planar microchem ical sensors based on Kapton(R) substrate to achieve the optimal analy tical performances, has been achieved. By storing the electrodes in co ntainers with humid atmospheres (100% humidity) their short time respo nses, e.g. measured potential, when placed in samples to be analyzed, are practically constant after one minute of immersion. The electrode sensitivity, potential reproducibility and membrane resistance of both pH and K+ sensors were evaluated and compared before and after placin g them in whole blood samples for specified periods of time. Blood ser um samples were successfully assayed and the results compared with tho se obtained with a pH glass electrode and a blood gas analyzer, respec tively. The long term stability of the membranes for in vivo use was i nvestigated by determination of cell adhesion and membrane biostabilit y (at 14 days of subcutaneous implantation in rats) using scanning ele ctron microscopy.