CAMBRIDGE, Mass.-MIT and University of Rochester researchers report important advances toward a therapeutic device that has the potential to capture cells as they flow through the blood stream and treat them. Among other applications, such a device could zapp cancer cells spreading to other tissues, or signal stem cells to differentiate.Their concept leverages cell rolling, a biological process that slows cells down as they flow through blood vessels. As the cells slow, they adhere to the vessel walls and roll, allowing them to sense signals from nearby tissues that may be calling them to work. Immune cells, for example, can be slowed and summoned to battle an infection.