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.
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