Wednesday, November 01, 2006

Cell Burst

How ultrasound slips drugs into cells

By Emily Singer

Ultrasound breaks through the left side of a prostate cancer cell. (Credit: Robyn Schlicher, Robert Apkarian, and Mark Baran)

Someday, your doctor may try to rip holes in your cells to get drugs inside. Scientists have long known that ultrasound (at lower frequencies than the ones used for medical imaging) helps get drugs inside cells, but these photos, of prostate cancer cells, are the first to show the process in action. Using several types of microscopy, researchers from the Georgia Institute of Technology showed that ultrasound waves punched holes in the cells' membranes. The pressure of the ultrasound creates tiny bubbles, says Mark ­Prausnitz, the professor in the School of Chemical and Biomolecular Engineering who led the work. When the bubbles burst, a wave of fluid movement opens up a small breach. The damage is temporary: researchers found that within minutes, the cells could manufacture and dispatch tiny spheres of membrane material that would patch the holes. The ultrasound technique could become a way to target delivery of gene therapy or chemotherapy to specific tissues, or to transport large-­molecule drugs that can't otherwise pass through cell membranes. Ultrasound wands could be pressed against the skin, with their energy focused on specific internal tissues. Safety studies are likely to take several years, says ­Prausnitz, but if all goes well, this could become an approved procedure in five to ten years.