Microfluidic devices for cell based high throughput screening.

Cell based screening assays are increasingly used in drug discovery due to the physiological significance of the results and high content information obtained from them. Miniaturization of this format, currently carried out in microwell plates, is at its limit due to increased unnatural interaction of cells with walls inside micro-wells. In order to overcome this limitation, we present a new format for dynamically controlled, precise, spatial and temporal dosing of a continuous cell culture layer, using microfluidics. The device consists of a micropatterned nanoporous membrane layer that allows specific spatial locations in the continuous gel layer above, to be chemically addressed by external electric field through a microfluidic network below it. We demonstrate that the control of electric field across the nanoporous membrane leads to extremely precise dosing (approximately 50 microg accuracy). Spot sizes of 200 microm to 6 mm in diameter and inter-spot distances of 0.4-10 mm have been obtained. Microarray spot densities of 156 spots/cm(2) were obtained, which is five times higher than the densities used in current cell based assays. The capability of this method in handling small molecules, proteins and drugs is also demonstrated. This format of spatial dosing of continuous cell culture will enable further miniaturization of cell based assays and aid in high-throughput high-content screening.