Melanin, the pigment that provides the color in our skin and hair, also plays key roles in protecting skin from ultraviolet (UV) light and repairing skin wounds. Now, researchers report that they’ve created a synthetic version of melanin—what they’re calling “super melanin” —that when applied as a skin cream nearly doubles the speed of skin healing following injury. The compound, described today in Regenerative Medicine, could offer dermatologists a powerful new tool for treating and even preventing skin damage from overexposure to the Sun, radiation therapy, or chemical burns.
“It’s a really exciting result,” says Luis Garza, a dermatologist at the Johns Hopkins University School of Medicine who was not involved in the study. Although there are already plenty of UV-absorbing sunscreens on the market, Garza notes that once damage occurs, clinicians have few tools to speed skin healing beyond skin grafts for the most severe cases. “Clearly, they are improving the wound response.”
Melanin is a single name that refers to a family of five closely related compounds. The most common of these, known as eumelanin absorbs UV light and suppresses compounds known as reactive oxygen species (ROS) that are generated by a sunburn or other types of skin damage. But natural levels of melanin, which vary among people in both type and quantities to produce different skin tones, often aren’t enough to prevent damage from overexposure to the Sun or other chemical irritants. That damage in turn triggers inflammation, swelling, and the release of a cascade of immune proteins that, among other things, break down scaffolding found in skin. During healing, anti-inflammatory immune cells eventually migrate to the region to calm the immune response.
Researchers led by dermatologist Kurt Lu and nanomaterials chemist Nathan Gianneschi, both at Northwestern University, set out to make souped-up versions of melanin to see whether they could help speed wound healing. The researchers started with dopamine, a derivative of an amino acid that’s also the starting point for melanin, and then followed two different strategies to link millions of copies of that compound together in order to produce versions that could sop up more ROS in a skin wound. One route involved forming tightly packed nanoparticles; the other created even smaller—but more porous—particles, leading to a bigger surface area over which they could interact with the skin. They then mixed tiny amounts of the two materials into separate batches of a commonly used skin cream.
The researchers applied the creams to mice that had been anesthetized and then exposed to nitrogen mustard (NM), a chemotherapy drug that is a chemical relative of mustard gas. When applied to the skin, the drug causes skin inflammation, redness, swelling and blisters that scab over—injuries that typically take 16 days or more to heal. When the researchers applied both types of their synthesized melanin creams to NM-treated mice, the animals’ injuries healed in 10 to 12 days. The treated animals’ injuries were also up to 50% smaller than controls.
Next, Lu, Gianneschi, and colleagues exposed a different set of mice to skin-damaging UV light and then administered the “super melanin” creams to the animals. Again, these mice recovered more quickly than mice that didn’t receive the “super melanin.”
Further investigation revealed that the “super melanin” had worked by soaking up ROS and dampening the mice’s immune response. “The treatment has the effect of setting the skin on a cycle of healing and repair, orchestrated by the immune system,” Lu says.
Finally, the researchers exposed patches of human skin cells that had been removed from patients during elective plastic surgery to NM. There were 20 patches in total; half were slathered in “super melanin” and the other half went untreated. The scientists once again saw the same dramatic results: All 10 of the untreated patches of skin rapidly developed blistering burns. Meanwhile, half of the skin samples treated with the cream containing the tightly packed, lower surface area particles showed no blistering whatsoever, whereas the other half developed mild blisters. This effect was less pronounced in the samples treated with the cream containing the more porous, higher surface area particles.
Despite that, it’s still unclear which method for making the “super melanin” produces the best results. In a nonanimal assay, the cream made up of the more porous “super melanin” particles proved more effective at mopping up ROS, likely because of the particles’ higher surface area, Gianneschi says. In the mice, it was also better at recruiting anti-inflammatory cells that speed healing.
Garza says the new cream could prove a welcome tool for doctors treating burn patients of all kinds. “There is not a lot we do for burns other than supportive care,” such as wrapping it loosely to avoid further damage, Garza says. The “super melanin” could be “something unique” he adds, because it appears to both prevent skin damage and speed repair.
The Northwestern team, which has recently launched a company to commercialize the material, says studies of the potential protective effects of “super melanin” are ongoing, including testing whether it prevents sunburns better than normal sunscreens. “It could help a lot of people,” Garza says.
