October 6, 2021 – Most vaccines is administered by injection of the needle. But shots are not necessarily the most effective or efficient way to get a vaccine. Scientists have been experimenting with micro-needle patches to deliver a vaccine painlessly into the outer layer of the skin with dozens of very small needles covered in the vaccine solution.
Now researchers have found a 3D printing method that allows them to adapt microneedle shapes in the spots to different pathogens, such as flu, measles, hepatitis, or COVID-19. In tests with mice, the spots resulted in stronger and longer-lasting immune responses than traditional shots under the skin. The research team describe their findings in the Proceedings of the National Academy of Sciences.
Small needles, big advantages
Previous research has shown that the administration of vaccines into the skin can elicit a stronger immune response because the skin has a high concentration of immune cells. But shots can be painful and require skilled medical providers.
Microneedles deliver the vaccine painlessly into the skin without the need for a trained physician. A person can even give the vaccine to himself.
The needles – made of metal, silicone or plastic – are so small that they penetrate only the sticky outer layer of skin. The prospect of a painless vaccination without an internal needle may decrease anxiety in people who fear needles.
Scientists can also store dried patches after covering them with the vaccine solution, so that no preparation is required before the vaccine is administered, and the patches may not even require cold storage. This latest study suggests that the patches generate a stronger immune response than standard shots, allowing for a smaller dose than traditional methods of administering vaccines and possibly fewer side effects.
The shape breaks
Previous methods of making microneedle patches often used molds, but this approach limited the possibility of adapting patches for different diseases. By using the same shape repeatedly, the small needles can also become blunt.
For the 3D-printed patches, Cassie Caudill at the University of North Carolina at Chapel Hill and her colleagues use a printing technique that greater control over and consistency in the shape of the microneedles. The investigators printed two shapes: a slender pyramid microneedle similar to previous versions, and one with serrated grooves that look like a pine tree.
The larger surface area of the grooves allows researchers to add 36% more of the ingredient that elicits an immune response, compared to using only the pyramid shape, but still less than a normal shot. Each patch contains only 1 centimeter by 1 centimeter 100 microneedles that are just over 1 millimeter long. The researchers found that the patch in mice has a stronger immune response than a normal shot, despite the fact that it contains a much smaller dose of vaccine ingredient.