Heat-activated pump could enhance drug-delivery patches

Purdue University researchers have developed a new type of pump for drug-delivery patches that could work in tandem with arrays of microneedles to deliver a wider range of medications.

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 auto-immune disorders, you can’t take orally because they aren’t absorbed into the blood system through the digestive tract.’

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

The patches require a pump to push the drugs through the needles, which have a diameter of about 20 microns. 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 added.

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 vapour, exerting enough pressure to force drugs through the microneedles.

The liquid is contained in a pouch separated from the drug by a thin membrane made of polydimethylsiloxane.

The researchers have filed an application for a provisional patent on the device and Ziaie has tested prototypes with fluorocarbons.

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

Findings indicate prototypes using the fluorocarbon HFE-7000 exerted 4.87lb/in2 and another fluorocarbon, FC-3284, exerted 2.24lb/in2.

The research findings are detailed in a paper due to be presented during the 14th International Conference on Miniaturized Systems for Chemistry and Life Sciences on 3-7 October at University of Groningen in the Netherlands.

The paper was written by electrical and computer engineering doctoral students Charilaos Mousoulis and Manuel Ochoa and Ziaie.