Harvard Heart Letter

Nanoburrs seek, heal injury in artery

Imagine a legion of microscopic healers patrolling the bloodstream to find and fix injured artery walls. That's the idea behind tiny drug-carrying particles called nanoburrs that have been developed by a team from the Massachusetts Institute of Technology and Harvard Medical School.

Nanoburrs are spheres 60 billionths of a meter (60 nanometers) in diameter. Thousands of them could sit on the period at the end of this sentence. Each has an inner core containing a drug linked to a slowly degradable polymer known as polyethylene glycol. The core is surrounded by a single layer of fat derived from soybeans. The outer wall is another polymer that protects the particle as it travels through the bloodstream. Coating the outer wall are protein fragments that resemble burrs, the hooks that bristle around the outside of certain seeds. In this case, the researchers created burrs that stuck to proteins found in the lining of blood vessels. In a healthy artery, these proteins are hidden by other tissues. In an injured artery, they are exposed to nanoburrs circulating through the bloodstream.

In tests in rats, nanoburrs injected into blood vessels in the tail found their way to damaged sections of the carotid artery in the neck. They settled down and released the stored drug over a two-week period (Proceedings of the National Academy of Sciences, Feb. 2, 2010).

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