In a new study, scientists at Northwestern University show that their synthetic melanin, mimicking the natural melanin in human skin, can be applied topically to injured skin, where it accelerates wound healing. These effects occur both in the skin itself and systemically in the body. When applied in a cream, the synthetic melanin can protect skin from sun exposure and heals skin injured by sun damage or chemical burns.
The synthetic melanin is being applied to inflamed skin; just under the surface of the skin are green free radicals, also known as reactive oxygen species (ROS). Image credit: Yu Chen, Northwestern University.
Melanin in humans and animals provides pigmentation to the skin, eyes and hair.
The substance protects your cells from sun damage with increased pigmentation in response to sunlight — a process commonly referred to as tanning.
That same pigment in your skin also naturally scavenges free radicals in response to damaging environmental pollution from industrial sources and automobile exhaust fumes.
“People don’t think of their everyday life as an injury to their skin,” said Northwestern University’s Professor Kurt Lu, co-senior author of the study.
“If you walk barefaced every day in the Sun, you suffer a low-grade, constant bombardment of ultraviolet light. This is worsened during peak mid-day hours and the summer season. We know sun-exposed skin ages versus skin protected by clothing, which doesn’t show age nearly as much.”
The skin also ages due to chronological aging and external environmental factors, including environmental pollution.
“All those insults to the skin lead to free radicals which cause inflammation and break down the collagen. That’s one of the reasons older skin looks very different from younger skin,” Professor Lu said.
When Professor Lu and colleagues created the synthetic melanin engineered nanoparticles, they modified the melanin structure to have higher free radical scavenging capacity.
Once applied to the skin, the melanin sits on the surface and is not absorbed into the layers below.
“The synthetic melanin is capable of scavenging more radicals per gram compared to human melanin,” said Northwestern University’s Professor Nathan Gianneschi, co-senior author of the study.
“It’s like super melanin. It’s biocompatible, degradable, nontoxic and clear when rubbed onto the skin.”
“In our studies, it acts as an efficient sponge, removing damaging factors and protecting the skin.”
The researchers envision the synthetic melanin cream being used as a sunscreen booster for added protection and as an enhancer in moisturizer to promote skin repair.
“It protected the skin and skin cells from damage,” Professor Gianneschi said.
“Next, we wondered if the synthetic melanin, which functions primarily to soak up radicals, could be applied topically after a skin injury and have a healing effect on the skin? It turns out to work exactly that way.”
The scientists discovered that the synthetic melanin cream, by soaking up the free radicals after an injury, quieted the immune system.
The stratum corneum, the outer layer of mature skin cells, communicates with the epidermis below.
It is the surface layer, receiving signals from the body and from the outside world.
By calming the destructive inflammation at that surface, the body can begin healing instead of becoming even more inflamed.
“The epidermis and the upper layers are in communication with the entire body. This means that stabilizing those upper layers can lead to a process of active healing,” Professor Lu said.
The authors used a chemical to create a blistering reaction to a human skin tissue sample in a dish.
The blistering appeared as a separation of the upper layers of the skin from each other.
“It was very inflamed, like a poison ivy reaction,” Professor Lu said.
They waited a few hours, then applied their topical melanin cream to the injured skin.
Within the first few days, the cream facilitated an immune response by initially helping the skin’s own radical scavenging enzymes to recover, then by halting the production of inflammatory proteins.
This initiated a cascade of responses in which they observed greatly increased rates of healing.
This included the preservation of healthy skin layers underneath. In samples that did not have the melanin cream treatment, the blistering persisted.
“The treatment has the effect of setting the skin on a cycle of healing and repair, orchestrated by the immune system,” Professor Lu said.
The team’s work was published in the journal npj Regenerative Medicine.
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D. Biyashev et al. 2023. Topical application of synthetic melanin promotes tissue repair. npj Regen Med 8, 61; doi: 10.1038/s41536-023-00331-1
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