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No Needle Needed

Reprinted from PN August 2012

Researchers have engineered a device that delivers medicine through the skin without use of a needle.

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Going to the doctor for a vaccination or giving yourself a dose of insulin may soon involve a little less pain, thanks to researchers at the Massachusetts Institute of Technology (MIT).

The MIT researchers have engineered a device that delivers a tiny, high-pressure jet of medicine through the skin without the use of a hypodermic needle. The device can be programmed to deliver a range of doses to various depths — an improvement over similar jet-injection systems that are now commercially available. 

Besides the obvious benefit to patients, the technology may help reduce the potential for needle-stick injuries to medical personnel. A needleless device may also help improve compliance among patients who might otherwise avoid the discomfort of regularly injecting themselves with drugs such as insulin.


The team reports on the development of this technology in the journal Medical Engineering & Physics.

Pushing Past the Needle

With the delivery of larger protein-based drugs on the rise, researchers have been developing new technologies capable of delivering them, including jet injectors, which produce a high-velocity jet of drugs that penetrate the skin. 

While several jet-based devices are on the market today, there are drawbacks to these commercially available devices, notes Catherine Hogan, a research scientist in MIT’s Department of Mechanical Engineering and a member of the research team.

The mechanisms they use, particularly in spring-loaded designs, are essentially “bang or nothing,” releasing a coil that ejects the same amount of drug to the same depth every time.

Breaching the Skin

Now the MIT team, led by Ian Hunter, the George N. Hatsopoulos Professor of Mechanical Engineering, has engineered a jet-injection system that delivers a range of doses to variable depths in a highly controlled manner.

The design is built around a mechanism called a Lorentz-force actuator — a small, powerful magnet surrounded by a coil of wire that’s attached to a piston inside a drug ampule. When current is applied, it interacts with the magnetic field to produce a force that pushes the piston forward, ejecting the drug at very high pressure and velocity (almost the speed of sound in air) out through the ampule’s very tiny nozzle.

The speed of the coil and the velocity imparted to the drug can be controlled by the amount of current applied; the MIT team generated pressure profiles that modulate the current. The resulting waveforms generally consist of two distinct phases: an initial high-pressure phase in which the device ejects the drug at a high-enough velocity to “breach” the skin and reach the desired depth, then a lower-pressure phase where a drug is delivered in a slower stream that can easily be absorbed by the surrounding tissue.

Through testing, the group found various skin types may require different waveforms to deliver adequate volumes of drugs to the desired depth.

“If I’m breaching a baby’s skin to deliver vaccine, I won’t need as much pressure as I would need to breach my skin,” says Hogan. “We can tailor the pressure profile to be able to do that, and that’s the beauty of this device.”

 

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No Needle Needed

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