Pump for Microneedle Drug-Delivery Patch

Babak Ziaie, a Purdue professor of electrical and computer engineering and biomedical engineering, shows a new type of pump for drug-delivery patches that might use arrays of microneedles to deliver a wider range of medications than is possible with conventional patches.Purdue University researchers have developed a new type of pump for drug-delivery patches that might use arrays of microneedles to deliver a wider range of medications than is possible with conventional patches. The current transdermal patches are limited to delivering drugs that, like nicotine, are made of small hydrophobic molecules that can be absorbed through the skin, says Babak Ziaie, a professor of electrical and computer engineering and biomedical engineering.

“There are only a handful of drugs that currently can be administered with patches,” Ziaie says. “Most new drugs are large molecules that willnot go through the skin. A lot of drugs, such as those for treating cancer and autoimmune disorders, you cannot take orally because they are not absorbed into the blood system through the digestive tract.”

Patches that used arrays of tiny microneedles could deliver a multitude of drugs, and the needles do not cause pain because they barely penetrate the skin, Ziaie explains.

“It is like a bandage – you would use it and discard,” Ziaie says.

The patches require a pump to push the drugs through the narrow needles, which have a diameter of about 20µm, according to Ziaie, or roughly one-fourth as wide as a human hair. However, pumps on the market are too complex for patches.

“We have developed a simple pump that’s activated by touch from the heat of your finger and requires no battery,” Ziaie states.

The pump contains a liquid that boils at body temperature so that the heat from a finger’s touch causes it to turn, rapidly, to a vapor, exerting enough pressure to force drugs through the microneedles.

“It takes 20 to 30 seconds,” Ziaie says. The liquid is contained in a pouch separated from the drug by a thin membrane made of a rubberlike polymer, called polydimethylsiloxane, which is used as diaphragms in pumps.

Researchers have filed an application for a provisional patent on the device.

Ziaie has tested prototypes with liquids called fluorocarbons, which are used as refrigerants and in semiconductor manufacturing.

“You need a relatively large force, a few pounds per square inch, to push medications through the microneedles and into the skin,” Ziaie states. “It is very difficult to find a miniature pump that can provide that much force.”

Findings indicate prototypes using the fluorocarbon HFE-7000 exerted 4.87psi and another fluorocarbon, FC-3284, exerted 2.24psi.

Details of the research findings were in a paper presented during the 14th International Conference on Miniaturized Systems for Chemistry and Life Sciences at University of Groningen, The Netherlands. The paper was written by electrical and computer engineering doctoral students Charilaos Mousoulis, Manuel Ochoa, and Babak Ziaie.

The research work gets support through funding from the National Science Foundation. Future research may include work to try the pump with microneedles.

Purdue University
West Lafayette, IN
purdue.edu/newsroom/research/2010/100831ZiaiePatches.html