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Nanoengineers develop the ‘ultimate natural sunscreen’

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Researchers at the University of California (UC) San Diego have developed nanoparticles that mimic natural cell structures to protect us from harmful ultraviolet (UV) radiation.

Long-term exposure to UV radiation can lead to premature ageing of the skin at best, and eye damage, immune system damage, DNA damage and skin cancer at worst.

Humans have natural defences against UV radiation in the form of melanosomes; cell structures responsible for producing, storing and transporting melanin, the pigment colouring our skin, hair and eyes.

Defects in melanin production can cause conditions such as vitiligo (where the immune system effectively halts the production of melanocytes) and albinism (the absence or defect in an enzyme necessary to produce melanin). These diseases do not currently have effective treatments, and result in a significant risk of skin cancer.

“The widespread prevalence of these melanin-related diseases and an increasing interest in the performance of various polymeric materials related to melanin prompted us to look for novel synthetic routes for preparing melanin-like materials,” said Professor Nathan Gianneschi, who led the team of nanoengineers, materials scientists and chemists.

An enormous range of melanin particles are produced in nature, pigmenting feathers, skin, eyes and scales. Extracting melanin from natural sources is a complex task, however, and many researchers have come to the conclusion that producing melanin in the lab could be an easier approach.

The researchers discovered that biocompatible, melanin-like nanoparticles could be synthesised through the oxidation of dopamine. This technique allowed for the controlled production of synthetic melanin, which mimics the behaviour of melanin found in bird feathers.

“We hypothesised that synthetic melanin-like nanoparticles would mimic naturally occurring melanosomes and be taken up by keratinocytes, the predominant cell type found in the epidermis, the outer layer of skin,” said Professor Gianneschi.

Once the researchers had produced the artificial melanin, they studied its transport, distribution and capabilities in human keratinocytes. They found that the nanoparticles were taken up and distributed through the skin, and protected the cells from DNA damage due to UV 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 behaviour of natural melanosomes,” said Professor Gianneschi.

“These systems have potential as artificial melanosomes for the development of novel therapies, possibly supplementing the biological functions of natural melanins,” the researchers report.

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