Acumen Journal of Sciences, May 20th, 2003
Sticklers for accuracy: Tiny needles provide better treatment for restenosis, diabetes and more.
News Analysis (The Acumen Journal of Sciences) — The hypodermic syringe hasn't changed much since its invention in 1853 - needles still hurt, and they deliver drugs to specific organs with little more accuracy than a shotgun. But advances in integrated circuit fabrication have made it possible to manufacture needles so tiny they can introduce highly accurate doses of a drug painlessly and, when necessary, with pin-prick precision.
Kirk Seward, chief technology officer of the start-up EndoBionics, began working on microneedles in 1999. He was a Ph.D. student at the University of California at Berkeley, studying with mechanical engineering professor Al Pisano, a former program manager for the microelectrical mechanical systems (mems) program at the Defense Advanced Research Projects Agency (darpa). Dr. Seward's background in catheters and mems manufacturing gave him the idea to integrate a microneedle into a catheter, creating a tiny syringe with many intriguing applications. "Our original thoughts were for heart disease or cancer therapies, where you don't want to have a lot of possibly toxic drugs washing through the system or getting filtered out by the kidneys and liver," he says.
Now, thanks to a cash infusion in late 2002 from the medical device firm Medtronic, EndoBionics is testing its trademarked MicroSyringe for use in treating restenosis. This renarrowing of the arteries occurs in about one-third of patients who undergo balloon angioplasty, stenting, or other coronary artery surgeries. To prevent restenosis, a drug-coated stent is often implanted at the time of the angioplasty.
EndoBionics proposes using a 1.5 mm-diameter catheter tipped with a balloon and threaded through a tiny incision in the patient's thigh. A 1 mm-long microneedle about 130 microns in diameter-the thickness of two or three human hairs-is attached and folded safely into the balloon's surface. When the catheter reaches the desired artery, the balloon is inflated and the microneedle penetrates the arterial wall, injecting its contents into the adventitia, the artery's outer layer of tissue.
Preliminary studies in pig arteries have shown that drugs delivered to the adventitia permeate the site of the blockage much more thoroughly than solid-form drugs from drug-coated stents. The company hopes to begin testing the device in humans next year and receive Food and Drug Administration approval for a restenosis application by 2005. Applications in other therapeutic areas will follow.
The microneedle can also make standard skin injections less painful and more precise. Dr. Pisano co founded the startup TheraFuse, which has developed a prototype insulin-delivery system about the size of a poker chip that attaches to the skin with adhesive. A preloaded, disposable capsule delivers insulin continuously through a 120-micron stainless steel microneedle. The device's pressurized reservoir propels the fluid, while a snap-in, reusable, chip-driven component meters the dosage. TheraFuse expects to start testing the device on animals in May 2003 and to have a product out by late 2005.
Still in the lab stage is the microneedle's most promising application of all: with funding from darpa and Becton-Dickinson, UC Berkeley bioengineering professor Dorian Liepmann has developed a tiny all-in-one syringe that shoots freeze-dried drugs into the skin painlessly through an array of up to 100 microneedles. Patients self-administer the doses by pushing the 10-mm-by-10-mm device-nicknamed the chiclet for what it resembles-against their skin for a few seconds, which forces the dry drug out of the reservoir, through the microneedle channels, and into the skin.
The chiclet's appeal for distributing vaccines and antibiotics in developing countries is enormous: the freeze-dried drugs don't require mixing, can be stored indefinitely, and can be distributed safely to patients to self-administer. It could also be used to deliver drugs that are dangerous or ineffective when taken orally, as a time-saving device for paramedics, for bioterrorism attacks, and in space. And it doesn't even hurt.
— Bonnie Azab Powell