Micro-needles could painlessly tattoo DNA vaccines into the skin

Patches covered in microscopic needles could tattoo vaccines into the skin to boost a patient’s defense against disease, researchers say.

Vaccines help bodies develop immunity to diseases by exposing immune systems to potential invaders. Scientists are now developing DNA vaccines that deliver genes from contagions into patients; the cells of vaccinated people then churn out molecules from those potential intruders that function like wanted signs, helping immune systems recognize dangerous threats.

In principle, DNA vaccines possess a number of benefits over regular vaccines. For example, instead of wasting time and resources generating and purifying proteins from germs for use in vaccines, manufacturers can simply get the human body to do the manufacturing work. However, so far DNA vaccines have not proven very effective in humans, perhaps because there has been no good way to give patients enough of the vaccine in a shot.

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Scientists have tried a number of strategies to make DNA vaccines more effective, for instance, using electrical zaps that make cells more permeable to DNA. However, this approach can be painful.

Instead, researchers at MIT sought to deliver DNA vaccines using arrays of microscopic plastic needles only 250 microns wide and 650 microns high. By comparison, the average human hair is about 100 microns wide.

Researchers coat these microneedles with biodegradable films containing the vaccine as well as a variety of other molecules, such as compounds that stimulate immune systems and help cells absorb DNA. Applying patches loaded with these needles onto the skin instantly embeds the coatings into the body, much like the application of a tattoo.

These microneedles can be designed to disrupt only the most superficial layers of the skin to avoid nerve endings and blood vessels, making them painless and safer than hypodermic needles.

"Comparing it to feeling like a cat's tongue is quite accurate," researcher Peter DeMuth, a biological engineer and materials scientist at MIT, told TechNewsDaily.

The coatings remain implanted even after the microneedle patches are pulled off. Coatings also dissolve in a controlled manner, releasing the vaccine and companion molecules over a sustained, and adjustable, period of time, which can be from days to weeks.

"We have very direct control over how the vaccine is delivered, and the prolonged exposure to the vaccine that is possible with this system can really enhance immunity," DeMuth said.

Scientists tested the patches on rhesus monkeys, measuring how much of a protein encoded by a DNA vaccine the animals would produce. The monkeys generated 140 times as much of the protein in response to microneedles  as they did when injected using normal, hypodermic needles.

"We brought together a number of interesting, different technologies, and the results are striking," DeMuth said.

Moreover, these patches can be stored at room temperature for weeks at end without loss of potency. This makes them more amenable to global distribution than solutions of vaccines, which demand refrigeration to stay active and are more expensive and complex to distribute.

The scientists detailed their findings online Jan. 27 in the journal Nature Materials.

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