Patch Designed for Vaccines, Cancer Treatments

Microneedle patch designed for vaccine and melanoma treatments (Celestine Hong and Yanpu He, MIT)

26 Aug. 2019. An engineering team designed a small skin patch with tiny needles that in lab mice quickly delivers vaccines and possibly treatments for melanoma. Researchers from Massachusetts Institute of Technology described the patch device yesterday, in a session of American Chemical Society’s national meeting in San Diego.

A team from the lab of MIT chemical engineering professor Paula Hammond is seeking better methods for delivering vaccines and treatments through the skin. Most topical ointments barely penetrate beyond the outermost skin layer and syringes use needles that can be painful to patients and are often difficult for individuals to properly administer to deliver drugs under the skin layer..

Hammond’s lab studies layer-by-layer construction of polymer devices, where the alternating charge in layers makes it possible to securely add a drug-laden film to a bio-compatible assembly. In this case the device has tiny microscale needles that penetrate the skin far enough to reach capillaries, yet remain painless to the recipient. This alternating charge property, however, creates problems if the drug needs to be delivered quickly.

Yanpu He, a graduate student in Hammond’s lab, says in an American Chemical Society statement that “this attraction makes the entire film very sticky. Past methods, which have retained this sticky nature, can take up to 90 minutes for a sufficient amount of drug to leave the patch and enter the skin.”

Hammond, He, and fellow graduate student Celestine Hong devised a solution that retained the layer-by-layer assembly method, but with materials that allow for much faster drug delivery. The team designed a new type of polymer for the device with two sections that add or lose a charge in response to the skin’s surface. As graduate student He explains, “The first part contains amine groups that are positively charged at the pH at which we make the microneedles, but that become neutral at the pH of skin.” Amines are bases derived from ammonia.

“The second part contains carboxylic acid groups,” He continues, “with no charge when the microneedles are made, but which become negatively charged when the patch is applied to the skin, so there is an overall change in charge from positive to negative.” The alternating charge is needed to construct the device, but in the presence of skin, changes the charge to all negative throughout the device, and repels the drug through the needles into the skin.

The researchers tested the patch with lab mice, using the protein ovalbumin, derived from chicken egg whites, as a reference. The team found ovalbumin delivered through the patch produced nine times the number of antibodies in mice as intramuscular injections, and 160 times the antibodies as injections under the skin. In tests with human skin samples, patch-delivered ovalbumin also invoked immune responses. And the deliveries happen quickly, in about a minute.

The researchers also devised a version of the patch to deliver drugs to treat melanona, an aggressive form of skin cancer. The team says they developed an antigen that works with the patch device, containing a biomarker protein over-expressed by melanoma tumors and an adjuvant that boosts an immune response. In early tests with healthy lab mice, antigens delivered through the patch appear to invoke an immune response in the skin of lab mice, which in turn could migrate to lymph nodes and stimulate a greater immune response. Further tests are planned in mice induced with melanoma tumors.

“We are using low-cost chemistry and a simple fabrication scheme to transform vaccination,” says Hammond. “Ultimately, we want to get a device approved and on the market.”

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