The patches were shown at the annual meeting of the American Chemical Society (ACS) by Mark Prausnitz of the Georgia Institute of Technology, US. Prausnitz and his colleagues created three variations of the basic design, which is a patch covered with rows of microneedles.
In one variant the microneedles are hollow. These internal spaces are used to store and deliver the drug or vaccine, in a design that is fairly similar to rows of tiny hypodermic needles.
The researchers believe this design could have applications in treating ocular diseases, such as macular degeneration. Repeated injections into the eye, which are currently needed to treat macular degeneration, are inconvenient and raise safety concerns.
Microneedles would only penetrate a short distance into the eye and Prausnitz thinks this could be as effective. Furthermore he believes that microneedles could be used to target specific tissues in the eye. Experiments in rabbits and non-human primates are underway.
Alternative uses and designs
An alternative design uses solid metal microneedles that are coated with a drug or vaccine. When the patch is applied the microneedles pierce the skin and the therapeutic coating is absorbed into the bloodstream.
The third design also uses solid microneedles but these are made out of a highly water soluble polymer. Encapsulated in the microneedles is the drug or vaccine. When these microneedles pierce the skin they dissolve, releasing the therapeutic into the body.
Prausnitz’ team are investigating the use of these patches in the delivery of seasonal influenza vaccines. They believe that the inconvenience of arranging an appointment at a clinic limits the number of people who are immunised each year and that microneedles can overcome this.
Patches could be collected from a pharmacy or delivered to the patient and self-administered, according to Prausnitz. Vaccine delivery has been trialled in mice and human trials are planned for 2010.
The researchers are also working with the Centers for Disease Control and Prevention (CDC) and hope to develop the patches for delivering polio and measles vaccines.
To ensure this is viable the researchers have designed the patches so they could be cost competitive against hypodermics when mass produced. The patches have the advantage that minimal training is required to use them.