You'd be hard pressed to find anybody who would complain if scientists developed an alternative to the necessary evil of getting a jab at the doctor's. Microneedle patches or jet-injectors could be good ways to painlessly deliver drugs through the skin, and now researchers at the University of California, Berkeley have developed the MucoJet, a pill-sized device that blasts vaccines through the inside of the cheek without pain or a professional.

The MucoJet is a 15 mm (0.6 in) cylinder with a 7 mm-wide (0.3 in) bulb on the end, and using it is a little like cracking a glowstick. A patient squeezes gently on the bulb to break a thin membrane separating two compartments: one filled with water and the other, a dry chemical propellant composed of citric acid and baking soda. When these mix, they fizz up, generating enough pressure to push on a piston in the cylinder, which forces a small reservoir of the vaccine out the other end through a small nozzle.

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If that's held against the inside of the cheek, the device has enough force to squirt the vaccine through the mucosal layer that lines it, which is notoriously difficult to penetrate without a needle. There, it's delivered into the waiting arms of antigen-presenting cells, a group of immune cells that help speed up the body's response to the invading pathogens.

"The jet is similar in pressure to a water pick that dentists use," says Kiana Aran, lead author of the study. "The pressure is very focused, the diameter of the jet is very small, so that's how it penetrates the mucosal layer."

The researchers first tested their new system in the lab, using cheek tissue from pigs, complete with the tricky mucosal layer. A protein called ovalbumin was the drug administered, and the experiments showed that three hours after vaccination, eight times more ovalbumin had been absorbed than in a control experiment using a dropper, which simulated how oral flu vaccines are administered. The studies also found that increasing the pressure of the jet improved the efficiency of the drug delivery.

Tested on live rabbits, the MucoJet system delivered seven times the amount of ovalbumin into the bloodstream as those treated with a dropper, and resulted in the production of far more antibodies, to the tune of three orders of magnitude.

While the researchers admit they didn't compare their new delivery system to the tried-and-true injection, they say the data indicates that the immune response should be at least as good as that given via a needle. Along with taking pain out of the equation, the MucoJet also reduces the biohazardous waste that comes from disposing of used needles, and can be administered at home by the patient, without needing a medical professional on hand.

While the next step is to test the system on larger animals, the researchers are also experimenting with different shapes and sizes for the device, including a version that can be swallowed to deliver drugs directly to the intestines, like the ingestible microneedle capsule in development at MIT. In the long run, it could even be hidden in candy, to make it more appealing to children.

"Imagine if we could put the MucoJet in a lollipop and have kids hold it in their cheek," says Aran. "They wouldn't have to go to a clinic to get a vaccine."

But the researchers estimate we'll still have to put up with needles for about five to 10 more years.

The research was published in the journal Science Translational Medicine, and the team describes the MucoJet in the video below.

Source: UC Berkeley

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