With a few experimental exceptions, bandages generally just cover wounds, as opposed to actively healing them. That's not the case with a new heat-activated "active adhesive dressing" (AAD), however, which forgoes antibiotics while mimicking embryonic skin.
Up to a certain point in their development, embryos don't get scars when their skin wounds heal. This is because skin cells around such wounds produce fibers made of a protein known as actin. These fibers contract, thus healing the wound by pulling its edges together. No scar tissue is produced.
Working with colleagues at Montreal's McGill University, scientists at Harvard University set about replicating this process in a bandage. The resulting AAD is made of an adhesive alginate (algae-derived) hydrogel, to which has been added silver nanoparticles and a thermoresponsive polymer called PNIPAm. That polymer not only repels water, but it also shrinks at a temperature of about 90 ºF (32 ºC).
When applied to a wound, the hydrogel bonds strongly with the skin. Additionally, that body-temperature skin heats the PNIPAm, causing the gel to contract. The adhered underlying skin contracts with it, quickly and effectively drawing the wound closed. Most of any potentially infection-causing bacteria, meanwhile, are killed by the silver nanoparticles.
By varying the amount of PNIPAm in the gel, the extent to which it pulls the skin together can be adjusted. This sort of control could come in handy, as the skin on joints such as the elbow would need to remain more stretchable and flexible while healing, as opposed to that on flatter parts of the body.
In lab tests, the AAD was found to adhere to pig skin with 10 times the force of a Band-Aid. It also reduced the wound-size area on mice by around 45 percent, while untreated wounds on a control group saw almost no reduction over the same time period. Additionally, it closed wounds faster than other experimental healing hydrogels that were tested, plus it produced no inflammation or immune responses.
"We are continuing this research with studies to learn more about how the mechanical cues exerted by AAD impact the biological process of wound healing, and how AAD performs across a range of different temperatures, as body temperature can vary at different locations," says Harvard's Dr. Benjamin Freedman, lead scientist on the project. "We hope to pursue additional preclinical studies to demonstrate AAD's potential as a medical product, and then work toward commercialization."
A paper on the research was recently published in the journal Science Advances.
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