Extracellular measurements of averaged ionic currents with the light-addressable potentiometric sensor (LAPS)

The light-addressable potentiometric sensor (LAPS) is a silicon-based detector which allows for measuring the electric potential distribution along its surface. The point of measurement is determined by illumination with a pulsed light source, and therefore the surface potential distribution can be measured spatially resolved by raster scanning a light-pointer along the surface. In this study electrically excitable neuronal cells (N1-E115 cell line) were grown on top of the surface of the LAPS. Individual cells were electrically stimulated using a patch clamp pipette. The light-pointer was focused on the stimulated cell and the electric potential of the silicon surface below the stimulated cell was recorded with the LAPS. Averaged extracellularly recorded signals were found to correspond with the intracellularly recorded patch clamp signals. Although it was possible to record averaged ionic currents of individual cells with the LAPS technique, the low signal-to-noise ratio so far hampers practical applications.