Science: Researchers are experimenting with a new method of using nanoparticles to clear obstructed blood vessels. They coated clumps of tiny synthetic polymers with tissue plasminogen activator (tPA). When injected into the bloodstream, the particles “flow freely in the blood and gravitate toward blocked vessels by sensing a change in blood flow,” writes Krystnell Storr for Science. Once they’ve located a clot, the polymer clumps break apart and the individual particles stick to the clot and release the tPA, which dissolves it. Tests on mice showed that the injected particles were able to reopen blocked vessels quickly, without causing the uncontrolled bleeding associated with traditional blood thinners. “The particles could be used to deliver essentially any drug—an anti-inflammatory to a specific spot where inflammation was occurring, for example,” said Donald Ingber of Harvard University, one of the authors of the paper published yesterday in Science.