Dr. Nadine Barrie Smith, assistant professor of bioengineering, says, "The new Penn State ultrasound patch, which operates in the same frequency range as the large commercially available sonic drug delivery devices, is about an inch-and-a-half by an inch-and-a-half in size and weighs less than an ounce. Commercially available sonicators currently have a probe about eight inches long which weighs over two pounds."
Experiments with human skin and with live rats have shown that the new ultrasound patch delivers therapeutically effective doses of insulin.
The new prototype is described in detail in "Transducer Design for a Portable Ultrasound Enhanced Transdermal Drug-Delivery System," published in the current (October) issue of the IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.
The key to the new ultrasound patch is a "cymbal" transducer developed by Dr. Robert Newnham, the Alcoa professor emeritus of solid state science. The transducer produces the sound waves that drive the medication through the skin and into the blood stream. The cymbal transducer consists of a thin disk of piezoelectric ceramic material sandwiched between titanium end caps shaped like cymbals. Four of these transducers are used in the prototype.
A thin reservoir of insulin is placed in front of the cymbal transducer and when a current is applied, sound waves just above the level of human hearing push the medication through the skin and into the blood vessels.
Smith notes, "Our experiments with rats show that an exposure of 20 minutes produced the same result as a 60-minute exposure. So, we are hopeful that, eventually, we may be able to tune the system so that one to five minutes of exposure may be enough."
Currently, diabetics must either inject insulin via hypodermic needles or use a mini-pump with a catheter that remains implanted in their body. Ultrasound offers a less painful and invasive alternative.
Besides insulin, some medications used to treat AIDS, pain relievers, asthma drugs, and hormones are deliverable via ultrasound, Smith adds. Those medications and, perhaps, some others that cannot be taken by mouth, are candidates for administration via the new ultrasound patch.
Her co-authors are Emiliano Maione, graduate student; Dr. K. Kirk Shung, professor of bioengineering; Dr. Richard J. Meyer, research associate at Penn State's Applied Research Laboratory (ARL); Dr. Jack W. Hughes, ARL Senior scientist and professor of acoustics; Newnham; and Smith. The rat experiments are described in "Ultrasound Mediated Transdermal in vivo Transport of Insulin with Low Profile Cymbal Arrays," presented this month at the IEEE 2002 Ultrasonics Symposium in Munich, Germany. The authors are Seungjun Lee, graduate student, Smith and Shung.
The research was supported, in part, with laboratory start-up funds provided to Smith by the University.