Defects in melanin production in humans can cause diseases such as vitiligo and albinism that lack effective treatments, while too much sun is a risk factor for cancers like melanoma. Vitiligo develops when the immune system wrongly attempts to clear normal melanocytes from the skin, effectively stopping the production of melanocytes. Albinism is due to genetic defects that lead to either the absence or a chemical defect in tyrosinase, a copper-containing enzyme involved in the production of melanin. Both of these diseases lack effective treatments and result in a significant risk of skin cancer for patients.
The team discovered that synthetic melanin-like nanoparticles could be developed in a precisely controllable manner to mimic the performance of natural melanins used in bird feathers. In healthy humans, melanin is delivered to keratinocytes in the skin after being excreted as melanosomes from melanocytes. They prepared melanin-like nanoparticles through the spontaneous oxidation of dopamine--developing biocompatible, synthetic analogues of naturally occurring melanosomes. Then they studied their update, transport, distribution and ultraviolet radiation-protective capabilities in human keratinocytes in tissue culture.
The researchers found that these synthetic nanoparticles were not only taken up and distributed normally, like natural melanosomes, within the keratinocytes, they protected the skin cells from DNA damage due to ultraviolet radiation.
"Basically, we succeeded in making a synthetic version of the nanoparticles that our skin uses to produce and store melanin and demonstrated in experiments in skin cells that they mimic the behavior of natural melanosomes," said Nathan Gianneschi, a professor of chemistry at UC San Diego.
The study was supported by a grant from the Air Force Office of Scientific Research (FA9550-11-1-0105).