Getting (drugs) under your skin using ultrasound

Using ultrasound waves, MIT engineers have found a way to enhance the permeability of skin to drugs, making transdermal drug delivery more efficient. This technology could pave the way for noninvasive drug delivery or needle-free vaccinations, according to the researchers.

Ultrasound waves of two different frequencies generate tiny bubbles of water on the skin's surface. When these bubbles pop, the skin's surface is lightly worn away, allowing drugs to pass through the skin more easily. Graphic: Carl Schoellhammer

''This could be used for topical drugs such as steroids - cortisol, for example - systemic drugs and proteins such as insulin, as well as antigens for vaccination, among many other things,'' says Carl Schoellhammer, an MIT graduate student in chemical engineering and one of the lead authors of a recent paper on the new system.

Ultrasound - sound waves with frequencies greater than the upper limit of human hearing - can increase skin permeability by lightly wearing away the top layer of the skin, an effect that is transient and pain-free.

In a paper appearing in the Journal of Controlled Release, the research team found that applying two separate beams of ultrasound waves - one of low frequency and one of high frequency - can uniformly boost permeability across a region of skin more rapidly than using a single beam of ultrasound waves.

Senior authors of the paper are Daniel Blankschtein, the Herman P. Meissner '29 Professor of Chemical Engineering at MIT, and Robert Langer, the David H. Koch Institute Professor at MIT. Other authors include Baris Polat, one of the lead authors and a former doctoral student in the Blankschtein and Langer groups, and Douglas Hart, a professor of mechanical engineering at MIT.

Two frequencies are better than one
When ultrasound waves travel through a fluid, they create tiny bubbles that move chaotically. Once the bubbles reach a certain size, they become unstable and implode.