Generation of chip based microelectrochemical cell arrays for long-term and high-resolution recording of ionic currents through ion channel proteins

• All processes necessary for waver-scale manufacturing of micoelectrochemical cell arrays consisting of cells with volumes of 30 pL and cell opening of 6–16 μm have been implemented.
• 3-D undercut structures containing nanocrystalline silver/silverchloride microelectrodes are generated.
• With the 3D microchamber structure, the electrodes can be used for stable long-term, high resolution current recording.
• Ionic current flowing through single alpha-hemolysin nanopores is successfully recorded with high resolution.

High throughput and a long life-time of the devices are two crucial challenges in planar chip technology for electrophysiological measurements of ionic current recording through ion channel proteins. In this paper, we present a wafer-scale process for the generation of novel arrays of microelectrochemical cells for long-term and high-resolution current recording. At the bottom of each of the cells, which have typically diameters of around 60 μm and volumes of around 30 pL, a nanocrystalline silver/silver chloride secondary electrode is generated for ionic current recording. The top of the cell is closed by a lid containing a small (6–16 μm) opening which connects liquid in the chamber to a contacting liquid on the outside. The processes necessary for manufacturing such a chip through photolithography and wafer-scale bonding have been developed, the resulting structures were characterized and the procedures were optimized. Combining a large surface area of the electrode with a – in relation to the cell size – relatively large amount of silver/silver chloride allows for the recording of DC ionic currents for prolonged periods of time. First measurements were performed where the electrochemical cells were closed by model membranes containing single ion channel proteins. The currents generated by ions passing through these ion channels are reported. These measurements demonstrate the usefulness of the microelectrochemical cell array for long time ionic current recordings at – for these type of measurements – relatively high current levels.