Tumor cells circulating in a patient's bloodstream can yield a great deal of information on how a tumor is responding to treatment and what drugs might be more effective against it. But first, these rare cells have to be captured and isolated from the many other cells found in a blood sample. Many scientists are now working on microfluidic（微流体） devices that can isolate circulating tumor cells (CTCs), but most of these have two major limitations: It takes too long to process a sufficient amount of blood, and there is no good way to extract cancer cells for analysis after their capture.

A new device from researchers at MIT and Brigham and Women's Hospital overcomes those obstacles. Inspired by the tentacles of a jellyfish（水母，海蜇）, the team coated a microfluidic channel with long strands of DNA that grab specific proteins found on the surfaces of leukemia（白血病） cells as they flow by. Using this strategy, the researchers achieved flow rates 10 times higher than existing devices -- fast enough to make the systems practical for clinical use.

Using this technology, described in this week's issue of the Proceedings of the National Academy of Sciences, doctors could monitor cancer patients to determine whether their treatment is working.

"If you had a rapid test that could tell you whether there are more or less of these cells over time, that would help to monitor the progression of therapy and progression of the disease," says Jeff Karp, an associate professor of medicine at Harvard Medical School and co-director of the Center for Regenerative Therapeutics at Brigham and Women's Hospital in Boston.

This type of device could also enable personalized treatments: Once cells are isolated from a patient, doctors could test different drugs on them to determine which are most effective.

The new technology grew out of a collaboration between Karp's lab and that of Rohit Karnik, an associate professor of mechanical engineering at MIT. Lead authors of the paper are Weian Zhao, a former postdoc in Karp's lab and now an assistant professor at the University of California at Irvine; Cheryl Cui, a graduate student in the Harvard-MIT Division of Health Sciences and Technology; and Suman Bose, a graduate student in Karnik's lab.