https://phys.org/news/2018-10-tiny-pain-free-vaccinationsmicroneedles-nanoparticles.html

Du developed two types of microneedle systems: hollow microneedles that can inject nanoparticulate vaccines and microneedles that were coated with the vaccine. Both the type of microneedle and the type and physicochemical characteristics of the nanoparticles appeared to have important influences on the responses provoked in the immune system. Using hollow microneedles, Du for example found that smaller nanoparticles with controlled release properties correlated with a stronger effect. To test these effects and to find out what needles, particles and injection parameters worked best, Du measured antibody and immune cell responses in mice after each application. The stronger the antibodies and immune cell responses, the better the vaccine worked.

                                
                    
    
    Picture of coated (A) and hollow (B) microneedles. Credit: Leiden University

"Microneedles have proven to be a promising tool for vaccination. People can even apply the microneedles themselves, so the costs of immunisation for society may be significantly reduced," Du explains. Another reason costs could be cut down is because nanoparticulate vaccines can achieve a similarly strong immune response to a normal vaccine, but with a smaller dose. "This is because an antigen that is loaded with nanoparticles has stronger immunogenicity than a free antigen solution. The use of nanoparticles will therefore help reduce the necessary dose of the antigen and further decrease the costs of vaccination." Finally, Du believes that microneedles will increase the compliance of patients, because the application is non-invasive and pain free. "This will hopefully increase the coverage of vaccination," he adds. "If the research and future clinical studies are successful, the microneedle system may become a new generation of vaccination methods."