Pain-free vaccinations, insulin administration, and improved delivery of transdermal drugs may all be on the horizon thanks to a simple and old technology – ultrasound.

Researchers at MIT have found that ultrasound waves can increase permeability of the skin by wearing away the top layer.

This is a temporary, pain-free effect that allows drugs to pass through the skin more easily.

A brief explanation on how the phenomenon works; as ultrasound waves travel through fluid (i.e., water, or a liquid suspension containing a drug), they create moving bubbles that eventually reach a certain size and “pop.”

The fluid rapidly enters the space left by the bubble, which creates microscopic abrasions on the skin, increasing permeability.

Recent studies had focused on using low-frequency ultrasound waves to achieve this, but the effect was suboptimal. They caused non-uniform, scattered abrasions. High-frequency waves could not be used alone, as they lack sufficient energy to burst the bubbles. The engineers at MIT found that a combination of low and high-frequency waves optimized the effect.

Carl Schoellhammer, a chemical engineering graduate student at MIT who worked on the project, explains why:

The high-frequency ultrasound waves generate additional bubbles, which are popped by the low-frequency waves. The high-frequency ultrasound waves also limit the lateral movement of the bubbles, keeping them contained in the desired treatment area and creating more uniform abrasion.

The researchers tested this method of delivery using pig skin. They first treated the skin with dual-frequency ultrasound waves, then applied either glucose or insulin. They demonstrated a significant increase of delivery of both substances versus a single-frequency system–glucose absorption was 10 times better, and insulin absorption was 4 times better.

This new system has several potential applications in medicine, including pain-free administration of insulin, immunizations, and better delivery of drugs for skin conditions. Engineers at MIT are working on improving the system even further, and it will have to be tested on animals before moving to human trials. Such a system seems promising, and since single-frequency ultrasound systems had already been approved by the FDA, researchers are confident that this new system will also pass the safety tests.


Journal of Controlled Release