CELL-BASED SENSOR MICROELECTRODE ARRAY CHARACTERIZED BY IMAGING X-RAYPHOTOELECTRON-SPECTROSCOPY, SCANNING ELECTRON-MICROSCOPY, IMPEDANCE MEASUREMENTS, AND EXTRACELLULAR RECORDINGS

We are developing a cell-based biosensor consisting of a planar microe lectrode array that allows detection of extracellular potentials and t heir modulation in the presence of toxins or other active agents. To i mprove cell-electrode coupling, the microelectrodes were electroplated with platinum black. We report on the use of imaging x-ray photoelect ron spectroscopy (XPS), scanning electron microscopy (SEM), impedance measurements, and extracellular recordings to assess the effectiveness of this procedure. SEM provided highly detailed images of the shape a nd structure of well-formed deposits of thickness on the order of 1 mu m or more. Because of its inherent high surface sensitivity, imaging XPS could reveal the presence of platinum deposits that were too thin to be detected by SEM. For typical, well-plated microelectrodes, imped ance measurements showed reductions in the electrical resistance at 10 0 Hz from roughly 60 M Ohm or more 1 M Ohm. The overall electronic cou pling of biopotentials to the microelectrodes was demonstrated by reco rdings obtained from beating rat myocytes and from rat spinal cord cel ls. (C) 1998 American Vacuum Society. [S0734-2101(98)06403-3].