The present invention is directed to a device for enriching cells with a cell surface marker, comprising an aptamer suitable for specifically binding the cell surface marker, and beads coupled thereto, wherein the aptamer is coupled to the beads in a manner that allows for release of cells expressing the cell surface marker, in the absence of a chemical agent, and production of a cell population enriched for cells expressing the cell surface marker, substantially free of beads and aptamer. Kits comprising the device or components thereof, and methods of cell enrichment, are also provided. In exemplary embodiments, the device contains an aptamer that specifically binds CD31.