Microneedles that dissolve after the work is done could improve both the safety and efficacy of vaccine-delivery systems. They could even allow untrained users to administer vaccines without causing pain, say researchers at Georgia Tech and Emory University. In studies on mice, the scientists are testing microneedle vaccinations compared with using traditional hypodermic needles.
 

Measuring 650 µm in length, the microneedles are designed into arrays that are applied to the skin. These arrays are made from polyvinyl pyrrolidone, a biocompatible polymer. To create a complete delivery system, the researchers mounted an array composed of hundreds of vaccine-infused microneedles onto a water-soluble patch. Freeze-dried influenza vaccine, in this case, was mixed with a vinyl-pyrrolidone monomer prior to placing it in the microneedle mold and polymerized at room temperature using UV light.
 

Once the patch is applied to a subject, the microneedles penetrate the outer layer of skin and dissolve into body fluids for vaccine delivery. The water-soluble backing is the only component of the complete system that remains. “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,” says Richard Compans, professor of microbiology and immunology at Emory University School of Medicine.
 

Using dissolvable microneedle systems instead of hypodermic needles to deliver vaccines could offer several benefits, the researchers note. For example, the dissolvable nature of the polymer reduces waste and eliminates the use of sharps. The technology also prevents the opportunity for reuse of hypodermic needles, according to the scientists, which is credited as being a contributing factor to the spread of HIV and hepatitis B in impoverished areas.

Microneedle-based systems could allow for self-administration of vaccines as well.
So far, the scientists’ research has shown that microneedle-based systems are as effective, if not more so, than hypodermic needles in mice. However, more studies are still needed, say researchers.