Electroanalytical and surface characterization of encapsulated implantable membrane planar microsensors

The selective polymeric membranes of planar microsensors sensitive to inorganic analytes of biomedical interest (e.g., H+, K+), fabricated on a flexible polyimide (Kapton® DuPont) substrate using a combination of thin-film, thick-film and packaging technologies, were encapsulated with a biocompatible polymeric material such as poly(2-hydroxyethylmethacrylate) (poly-HEMA), The electroanalytical characteristics of these sensors (linear activity ranges, slopes of the calibration curves, response times, membrane resistances, and selectivities) are not significantly different when compared with those of non-coated membrane sensors. The encapsulated membrane electrodes show improved analytical characteristics after exposure to whole blood samples for specified periods of time. The long-term stability of the membranes for in vivo use was investigated by the cage implant system; the membrane biostability and cell adhesion, at 1, 3, 7, and 14 days of subcutaneous implantation in Sprague-Dawley rats, were evaluated by scanning electron microscopy.