MIT-engineered device injects drug without needles, delivering a high-velocity jet of liquid that breaches the skin at the speed of sound. Image: MIT BioInstrumentation Lab |
Getting
a shot at the doctor’s office may become less painful in the not-too-distant
future.
Massachusetts
Institute of Technology (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.
The
researchers say that among other benefits, the technology may help reduce the
potential for needle-stick injuries; the Centers for Disease Control and
Prevention estimates that hospital-based health care workers accidentally prick
themselves with needles 385,000 times each year. 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.
“If
you are afraid of needles and have to frequently self-inject, compliance can be
an issue,” says Catherine Hogan, a research scientist in MIT’s Department of
Mechanical Engineering and a member of the research team. “We think this kind
of technology … gets around some of the phobias that people may have about
needles.”
The
team reports on the development of this technology in Medical Engineering
& Physics.
Pushing past the needle
In the past few decades, scientists have developed various alternatives to
hypodermic needles. For example, nicotine patches slowly release drugs through
the skin. But these patches can only release drug molecules small enough to
pass through the skin’s pores, limiting the type of medicine that can be
delivered.
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 there
are several jet-based devices on the market today, Hogan notes that there are
drawbacks to these commercially available devices. 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
ampoule. 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
ampoule’s nozzle—an opening as wide as a mosquito’s proboscis.
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 drug at a
high-enough velocity to “breach” the skin and reach the desired depth, then a
lower-pressure phase where drug is delivered in a slower stream that can easily
be absorbed by the surrounding tissue.
Through
testing, the group found that 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,” Hogan says. “We can tailor the pressure
profile to be able to do that, and that’s the beauty of this device.”
The
team is also developing a version of the device for transdermal delivery of
drugs ordinarily found in powdered form by programming the device to vibrate,
turning powder into a “fluidized” form that can be delivered through the skin
much like a liquid. Hunter says that such a powder-delivery vehicle may help
solve what’s known as the “cold-chain” problem: Vaccines delivered to
developing countries need to be refrigerated if they are in liquid form. Often,
coolers break down, spoiling whole batches of vaccines. Instead, Hunter says a
vaccine that can be administered in powder form requires no cooling, avoiding
the cold-chain problem.
Massachusetts Institute of Technology
Filed Under: Drug Discovery
