Soft-state integrated microfluidic patch-clamp array chip

The soft-state Integrated Microfluidic Patch-clamp Array Chip (IMPAC) with lateral junctions for electrophysiology and microfluidic circuit design for cell trapping capability have been successfully demonstrated for the first time. The IMPAC utilizes microfluidic junctions that are formed by two different fluidic sizes (2∼4 μm × 2∼4 μm and 500 μm × 50 μm) of microfluidic channels which allow creating two level fluidic circuits. The larger main microfluidic channel (i.e. low resistance) provides a path for effective cell loading and the smaller microfluidic patch channel (i.e. high resistance) is utilized to trap a cell via the lateral microfluidic junction. The negative pressure is applied through the patch channel for cell trapping. Once the cell is trapped at the junction, the patch seal is formed between the cellular membrane and microfluidic junction, which is fabricated by a soft-elastomeric polymer. A following suction (about 1-2 psi) enhances the sealing. The average patch seal resistance of the second generation of lateral patch-clamp device was 140 ± 20 MΩ. The whole cell current of Kv2.1 is recorded with the microfabricated patch-clamp and compared with that done by the conventional patch-clamp using a glass capillary. Our whole cell current measurement agrees well with the conventional methods.;In order to develop a highly sensitive patch-clamp device (i.e. low ionic current recordings) in electrophysiology, high seal resistance of giga ohm range is desirable. Various tests had been done and it is found that the geometry of the patch orifice is a critical element in the "giga ohm" seal formation. As far as the deformation of the trapped cell is concerned, a symmetric patch orifice can provide uniform deformation and increase seal resistance. The third generation of the lateral patch-clamp device is accomplished by a self-raised oval patch orifice. The average seal resistance of the self-raised oval patch orifice has increased up to 917 ± 108 MΩ and the maximum patch sealing resistance via the self-raised oval patch orifice was 2.77 GΩ. The patch seal is reliable enough to survive for 1 hr without any vibration-isolation system and suction.