Dissolving microneedle patches – clean, painless, longer-lasting vaccinations
By Loz Blain
July 20, 2010
Doctors have been using hypodermic needles for more than 150 years - but syringe vaccinations could be just about to be replaced by a simple patch you can stick on your arm with no medical supervision. The microneedle patches have an array of microscopic needles on them that penetrate the skin just deep enough to dissolve and deliver a vaccine without causing any pain. There's no sharp hazardous waste left over, they're no more expensive than a syringe, and most importantly, tests on mice are showing that microneedle vaccinations are significantly longer-lasting than deeper injections delivered by syringe.
Hypodermic needles are somewhere between 150 and 350 years old, and while they perform a critical function in modern medicine, they certainly have their drawbacks. For starters, you need to know exactly where to stick them, to make sure drugs are delivered to the right spot and nothing else is damaged – so you really need a medical professional to administer them. Then, once you're done, you've got a pointy little biohazard to deal with that could easily spread all sorts of diseases if it pokes somebody else. And let's not forget, while only a small percentage of people have a true fear of needles, they're really not all that pleasant for the rest of us either.
So biodegradable microneedle patches offer a real advance for certain applications – particularly vaccinations.
Microneedle patches are self-applied band-aid style adhesives that can be applied to any area of the skin. The active area is an array of tiny needles, just 650 microns in length, or 0.65mm. As the patch is applied to the skin, the microneedles penetrate the top layer of skin, but not deeply enough to activate any pain receptors.
Here's where things get really clever–- the microneedles are made from a harmless dissolving polymer that's mixed with a freeze-dried vaccine. So instead of the needles injecting a fluid, the needles quickly dissolve to become the fluid. When you pull the patch off, there's nothing sharp left on it, you can throw it straight in the bin without worrying that it'll be a hazard to others.
Recent tests using the microneedle patches to vaccinate mice against the influenza virus showed an extra benefit – it seems that the outermost layers of skin, where these patches drop their load of vaccine, are more effective sites for vaccination than the deeper layers you hit with a hypodermic needle.
"The skin is a particularly attractive site for immunization because it contains an abundance of the types of cells that are important in generating immune responses to vaccines," said Richard Compans, professor of microbiology and immunology at Emory University School of Medicine.
A joint study by researchers from Emory University and the Georgia Institute of Technology found that microneedle vaccination was just as effective as deep tissue injection in the short term, but that it was significantly more effective when the mice were exposed to the disease three months after vaccination.
So the advantages in a nutshell would appear to be:
- 1) No painful piercing of the skin
- 2) They can be self-applied, sold through the mail or over the counter
- 3) No sharp hazardous waste after immunization
- 4) More effective vaccinations
On top of this, the microneedle patches aren't expected to be any more expensive than the cost of a vaccine syringe - and they should end up offering a much cheaper process as they cut down on manpower and waste disposal requirements.
Naturally, clinical studies on humans are required before they can go into production, but at this stage, microneedle patches look like they make a lot of sense. I'm sure doctors would agree it'll all be worth it for every time they don't have to see that look of terror in a kid's eye.
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