Vaccine-loaded polymeric patches that, when applied to the skin, enable the simple delivery of DNA vaccines are reported online in Nature Materials this week.

Darrell Irvine, Paula Hammond and colleagues show that microneedle arrays can be combined with polyelectrolyte multilayer technology to enhance the delivery of DNA vaccines. This is as a result of the co-delivery of DNA with biological agents that promote the uptake of nucleic acids into cells. The polymeric microneedles are applied to the skin and implant biodegradable polyelectrolyte, vaccine-loaded thin films into the top layer of the skin. The polymer layer in contact with the skin dissolves on application, allowing the microneedle array to be easily and quickly removed. The implanted films release DNA and immunostimulatory RNA into the skin over a tunable period, which can be from days to weeks.

This microneedle, multilayer approach elicits immune responses in the body that far exceed naked DNA injections. Also, the microneedle patches can be stored in a dry state, at room temperature for weeks without loss of activity. Hence, the vaccine-loaded patches are more amenable for the global distribution of vaccines because refrigeration is not required and the embedded biological agents remain active for a significant time.