WEST LAFAYETTE, Ind. - 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 now 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, said 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," he said. "Most new drugs are large molecules that won't go through the skin. And a lot of drugs, such as those for treating cancer and autoimmune disorders, you can't take orally because they aren't 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, he said.
"It's like a bandage - you would use it and discard," Ziaie said.
The patches require a pump to push the drugs through the narrow needles, which have a diameter of about 20 microns, or roughly one-fourth as wide as a human hair. However, pumps on the market are too complex for patches, he said.
"We have developed a simple pump that's activated by touch from the heat of your finger and requires no battery," Ziaie said.
The pump contains a liquid that boils at body temperature so that the heat from a finger's touch causes it to rapidly turn to a vapor, exerting enough pressure to force drugs through the microneedles.
"It takes 20 to 30 seconds," Ziaie said.
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.
Research findings are detailed in a paper being pre
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