Pain-free needles!

Sep 28 2005

Millions of fearful patients could be saved the pain of vaccinations thanks to revolutionary pain-free needles to be revealed today for the first time at the British Pharmaceutical Conference in Manchester.

Scientists from the Welsh School of Pharmacy in Cardiff are working towards genetic vaccination, whereby DNA is introduced directly into cells, which leads to the production of an antigen that stimulates an immune response. So, rather than injecting antigen as with standard vaccines, the new method involves injection of DNA encoding for that antigen.

However, whilst researching this exciting new method, researchers came across a specific problem: the outer layer of skin (stratum corneum) has low permeability and poor retention of the injected DNA at the injection site.

To overcome this difficulty the Cardiff researchers teamed up with local clinicians and engineers at Tyndall National Institute, Ireland, to develop innovative pain-free microneedles that bypass the outer layer of skin. These needles are long enough to cross the permeability barrier, but not long enough to reach the pain receptors.

Dr James Birchall, Head of the Gene Delivery Research Group, explains: "The microneedles create temporary channels in the skin surface to allow vaccine into the immune-responsive skin layers. The idea is that the DNA will then produce its antigen which is recognised in the skin, producing an immune response."

To ensure that the DNA stays in place long enough to produce the optimum immune response, the researchers have designed a sustained release delivery system. Dr Birchall says: "Our idea was that having made microchannels, we could place a hydrogel containing the DNA into the channels. The gel will solidify in the channels, creating a reservoir of DNA vaccine in the skin."

As the hydrogel is designed to release DNA over a more prolonged period than using a solution or powder, this might lead to an enhanced immune response and possibly reduce the number of booster vaccines needed.

In in vitro studies launched at the Conference, the hydrogel/microneedle system was used to deliver a 'reporter' gene into 'live' human skin (obtained after surgery). The studies showed that the microneedles could successfully deliver DNA to the skin and that the injected DNA expressed its antigen. "These delivery platforms warrant further investigations for their potential in the administration of genetic vaccines via the skin," Dr Birchall said.

The next stage of the research will investigate delivery of vaccines such as hepatitis B and influenza.

DNA vaccines have several potential advantages over standard vaccines, Dr Birchall explains: "They are likely to be cheaper and easier to make. The microneedle system might also be developed as a patch for self-application, avoiding the need for a clinician.

"There is also reduced risk of transmission of blood-borne pathogens by inappropriate reuse of needles. These are all particular advantages for the developing world. But pain-free vaccination could also be useful for childhood vaccines in developed countries."

Dr Birchall concluded that the microneedle system might also be used to deliver DNA as gene therapy to treat cancer and genetic skin disease.