Scientists have long known melanin – the pigments that give colour to skin, hair and eyes – has numerous useful qualities, including providing protection from cancer-causing ultraviolet (UV) radiation.
Due to its inherently disordered structure, however, attempts at recreating it in the laboratory have been thwarted.
Now a group of scientists, including researchers from the University of Strathclyde and City University of New York (CUNY), have developed a new approach for producing materials that not only mimic the properties of melanin, but also provide unprecedented control over them.
The discovery, published today in the journal Science, could enable the development of new cosmetic and biomedical products.
Melanin is best-known for its role in giving colour to the skin and protecting it against the sun’s harmful rays but it also has other qualities, including electronic conductance, adhesiveness and the capacity to store energy.
Unlike other biopolymers, such as DNA and proteins, where a direct link exists between the polymers’ ordered structures and their properties, the structure of melanin is inherently disordered.
As a result directly relating structure to function is not possible, meaning researchers have been unable to fully exploit melanin’s properties.
To overcome this the research team used simple version of proteins – tripeptides consisting of just three amino acids – to produce molecular architectures with precisely controlled levels of order and disorder.
Lead researcher Professor Rein V. Ulijn, director of the Nanoscience Initiative at the Advanced Science Research Center (ASRC) at the Graduate Center, CUNY, said: “We were amazed to see that, upon oxidation of these peptide structures, polymeric pigments with a range of colors – from light beige to deep brown – were formed.”
Subsequent, in-depth characterisation of the approach demonstrated that further properties, such as UV absorbance and nanoscale morphology of the melanin-like materials, could also be systematically controlled by the amino acid sequence of the tripeptide.
Dr Tell Tuttle, Director of Research in the Department of Pure and Applied Chemistry at Strathclyde, employed computational technologies to characterise these materials and understand how these different structures could be created from the smaller building blocks of tripeptides.
He said: “Through our ability to control the structures formed by tripeptides we’ve created materials that display the various properties of melanin but which we can shape as we wish.
“This project combined the ASRC’s world-class facilities and experimental expertise with our computational expertise and the ARCHIE-WeSt supercomputer based at Strathclyde to produce materials that in many ways are better than melanin due to the control that we can exercise over them.”
The findings published in Science build on previous research conducted by Ulijn, who is also the Albert Einstein Professor of Chemistry at Hunter College and a member of the biochemistry and chemistry doctoral faculty at the Graduate Centre.
His lab will now turn its attention to further clarifying the chemical structures that form and expanding the resulting functionalities and properties of the various melanin-like materials they produce. The researchers are also pursuing commercialisation of this new technology, which includes near-term possibilities in cosmetics and biomedicine.
Funding for the research was provided in part by the US Air Force. Additional funding was provided by the Israeli Council of Higher Education (Postdoctoral Fellowship).