Although it's important to get vaccines to people in developing nations and elsewhere, it's also crucial that those medications subsequently be administered in a safe and sterile manner. A new microneedle patch could help, as it incorporates bacteria-killing silver.

Microneedle patches, which we've seen before in recent years, have some key advantages over hypodermic injections – among these are the facts that they're painless, they don't need to be refrigerated, and they don't result in hazardous "sharps" waste.

Each patch consists of a small square of material that has an array of tiny medication-containing needles on its underside. When the patch is applied to the patient like a band-aid, those microneedles pierce only the top layer of skin, not reaching any of the underlying nerves. The needles then harmlessly dissolve, releasing the medication into the bloodstream.

Developed by scientists at the University of South Australia, the new patch features a 15 x 15 array of microneedles, each one just 700 microns in length. Loaded with both a vaccine and silver nanoparticles, those needles are made of a biocompatible water-soluble polymer (carboxymethylcellulose), which completely dissolves within one minute of application. As a result, the medication is delivered, and bacteria in that area of the skin are eradicated.

In lab tests, the patch was found to kill off skin-infection-causing bacteria such as staphylococcus epidermis, escherichia coli and pseudomonas aeruginosa. The area of application subsequently remained bacteria-free for 24 hours.

"Infection from unsafe injection practices occurs all over the world, so technologies that protect people from unnecessary infection are critical," says lead scientist Prof. Krasimir Vasilev. "The dissolvable feature of our silver-loaded microneedles ensures absolutely no risk of reuse, removing one of the greatest causes of infection. And by incorporating the antibacterial silver nanoparticles into the dissolvable microneedles, we've created a very promising vehicle for safe vaccine and drug delivery around the world."

A paper on the research was recently published in the journal Chemical Communications.