A Microfluidic Approach Enables Ligand Gated Ion Channel Recording from Cell Ensembles

Abstract

Electrophysiology remains the preferred method for characterizing ion channel function and kinetics. For screening, it is the most functionally relevant assay, and supersedes flux and fluorescent assays in terms of information content. Many of the medium to high throughput pharmaceutical screens are performed using the ‘population patch’ approach, which measures current from as many as 64 cells in parallel, eliminating a good deal of the cell-to cell variability of single cell recordings. A major drawback of this method is the inability to exchange solutions during voltage clamp or apply multiple compounds to the same ensemble of cells.Here we present the first data showing that, by integrating an appropriate microfluidic network design, a large number of cells under voltage clamp can be exposed to a compound within short time scale (50ms) in parallel. A comparison between competing compound injection designs will be presented along with validation data for a number of important ion channel targets. The fluid dynamics of the microfluidic networks were characterized by measuring the time domain response of channel activation and block. Another important aspect that we addressed is the rate of adsorption and desorption of compounds from the channel surfaces. Small fluorescent molecules were used to measure the surface properties as a function of molecular LogP values.Continuous recording coupled with fast compound additions (50ms for a 20-cell ensemble) opens the way to ensemble recording for ligand gated ion channels, including fast desensitizing channels. We will present ion channel ensemble recording from cell lines expressing GABA-A, P2X3 and TRP-V1 that were obtained using this microfluidic approach.