October 6, 2021 – Most vaccines are given by injection under the skin. But injections are not necessarily the most effective or efficient way to deliver the vaccine. Scientists have been experimenting with microneedle patches to deliver a painless vaccine to the outer layer of the skin using dozens of tiny needles covered with a solution of the vaccine.
Now, researchers have found a 3D printing method that allows them to customize microneedle shapes in spots for different pathogens, such as influenza, measles, hepatitis or COVID-19. In tests in mice, the patches triggered stronger and longer-lasting immune responses than traditional subcutaneous shots. The research team described their findings in Proceedings of the National Academy of Sciences.
Small needles, big advantages
Previous research has shown that giving vaccines into the skin can cause a stronger immune response because the skin contains a high concentration of immune cells. But the injections can be painful and require skilled medical providers.
Microneedles deliver the vaccine to the skin painlessly without the need for a trained doctor. In fact, anyone can give the vaccine themselves.
The needles — made of metal, silicone, or plastic — are so small that they only puncture the tough outer layer of skin. The prospect of a painless vaccine without a hypodermic needle may ease anxiety in people who fear needles.
Scientists can also store dry patches after applying the vaccine solution, so there is no need to prepare before the vaccine is given and the patches may not require cold storage. This latest study indicates that the patches generate a stronger immune response than standard patches, allowing for a smaller dose than traditional vaccine delivery methods and possibly fewer side effects.
break the mold
Previous methods for making microneedle patches often used templates, but this approach limited the ability to assign patches to different diseases. Using the same mold repeatedly can also break up the tiny needles.
For the 3D-printed patches, Cassie Cuddle of the University of North Carolina at Chapel Hill and colleagues used a printing technique that allows greater control and consistency of the shape of the microneedles. The investigators printed two shapes: a thin pyramidal microneedle similar to previous versions, and another shape with serrated grooves resembling a pine tree.
The increased surface area of the grooves allows the researchers to add 36% more of the component that causes an immune response, compared to using only the pyramid shape, but still less than a conventional shot. Each patch contains 100 micro needles that are just over 1 millimeter long. The researchers found that in mice the patch elicits a stronger immune response than the conventional vaccine, even though it contains a much smaller dose of the vaccine ingredients.