Divvying Up the Dose
In spite of the fear, the pain, and the safety problems we're still mostly stuck with needles for getting injections. "Worldwide, around 12 billion injections are given each year, says University of California, Santa Barbara chemical engineer Samir Mitragotri. He says there's a good reason why current needle-free injectors have not largely replaced needles.
"The biggest problem is that the jet goes deep into the skin where it hits the blood vessel and nerves. And that causes bleeding and pain (This paper is a good example. Ouch!)," Mitragotri says. "Because of these reasons, they are not very popular."
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Illustration: Needle-less Injections - The next generation of injections may be delivered by devices look as gentle as they feel. |
Mitragotri has been working with engineers at StrataGent Life Sciences to test a needle-free device that even looks less frightening. It breaks a drug dose up into tiny microjets that barely penetrate the skin.
"Imagine a jet injector which is out there which delivers a large amount of drug instantly into the skin. What we do is take that amount of drug and divide it into many, many small doses, and each dose goes into the superficial skin layer." Mitragotri explains. "And that way we can deliver the same amount of drug, but do it without having to go deep into the skin."
They reported in Proceedings of the National Academy of Sciences that tests on a human skin substitute, human skin from cadavers, and animal tests using insulin as a model drug, showed it works. The device "can deliver sufficient quantities of insulin into the body for therapeutic applications," says Mitragotri.
While the device still needs to be tested in people, the researchers are confident that you won't even feel a little prick. While Mitragotri and his UCSB colleagues couldn't try the device on themselves due to university policies regarding human testing, co-author Ravi Srinivasan, a founder of StrataGent says he and some other Stratagent engineers did try the device with some harmless food coloring just to make sure it didn't hurt. "We have spent four or five years of our lives doing this and if we had not tried it ourselves we wouldn't have the courage to spend our lives on this company." But to know if the device can safely deliver drugs in people will take actual human clinical trials.
"You put it on the skin and if you notice very closely, you [feel] a little pressure on that point. But if you don't pay attention to it, you don't know what's going on," Srinivasan says.
Comparing the prototype microjet device with a conventional injector, the researchers injected blue dye into an agar gel which serves as a human skin substitute. While the microjets release the dye into just the top 100 microns of a flat petri dish of gel, it takes a large test tube of gel to demonstrate the conventional injector.
The device takes longer to deliver the same dose. For example, a flu shot or other vaccination could take a few seconds instead of an instant jab. (But think of the time savings in not having to chase terrified kids around the pediatrician's office!).
That will mean it won't be able to replace needles in situations where a large amount of drug is needed immediately, but StrataGent's Srinivasan says the device's ability to replace other types of drug delivery, such as on-the-skin or transdermal patches, will more than make up for that limitation. "We see these as more universal transdermal drug delivery systems and the capability of the device today is to deliver anything that's in a liquid form," says Srinivasan.
The commercial version of the device that Strategent intends to bring to market resembles a small computer mouse. It consists of two parts, one that's designed to last, which contains a microprocessor that can be programmed by a doctor or patient, as well as a battery. The other part, which contains the drug reservoir and microjet nozzles, is disposable.
"We are shooting for a durable [component] price-- it depends on the therapy, of course-- but a durable price of tens of dollars, and the disposable piece which is the one that will be used every day or three days, we want to make it a few dollars," Srinivasan says.
He says that will make it cost-effective compared to insulin pumps used by some diabetics, fentanyl patches used for cancer pain, or even a traditional flu shot.
"The insulin pump," says Srinivasan, "costs like $5,500 to $6,000 and that lasts about three years and so what we provide is a low barrier to entry for new patients and for insurance companies… if you take the fentanyl patch today for pain management in cancer patients, they have a three-day patch and that patch costs about 30 to 50 dollars depending on the dose… And if you take a flu shot, each one of those flu shots even with the syringe costs tens of dollars. And it's similar with insulin, too-- that's probably one of the most competitive markets in terms of price-- and the cost of insulin therapy for a day can go up to 10 dollars."
That initial cost will put it out of reach of developing countries where needle re-use is a major factor in spreading infectious diseases, he said, but added that the cost would likely come down in a few years, and that the company also plans to engineer different versions of the device for different uses
Srinivasan jokes that after trying the device out on themselves using safe food dyes, they think they might also be able to corner the temporary tattoo market. "That was one of the markets we go after on Friday afternoons," he laughs.
The company hopes to conduct human clinical trials in 2008 and possibly even have a "limited market release" later in the year.
This research was published in PNAS, March 13, 2007 and funded by the National Institute of Standards and Technology (NIST), National Collegiate Inventors and Innovators Alliance, and the Lemelson Foundation.
Interviewee: Samir Mitragotri, University of California, Santa Barbara; Ravi Srinivasan, StrataGent Life Sciences, Inc.
Length: 1 min 16 sec
Produced by: Joyce Gramza
Edited by: Sunita Reed/Chris Bergendorff
Accidental Needle Stick Statistics
Needle Re-Use and Infections
For Further Research
Stopping Bleeding (10.19.06)
Saliva Diagnostics (10.14.05)
Battlefield Band-Aids (03.25.03)
From ScienCentral, Inc., June 21, 2007, as published under license in AccessScience, © The McGraw-Hill Companies 2000-2007.
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