Electronic structure calculations boost melanin's potential as new biomaterial

Researchers from São Paulo, Brazil, and Catalonia presented innovations made possible by nanotechnology during FAPESP Week Barcelona.

By Diego Freire, in Barcelona

Agência FAPESP – A combination of electronic structure calculations, used to model the behaviour of electrons at the atomic level, and experimental techniques has deepened scientists’ understanding of melanin as a new material for bioelectronics.

No commercial applications have yet been developed for melanin but it shows significant potential. The biopolymer is responsible for hair and eye colour, as well as being found throughout nature, from fungi to human beings. Its capacity to conduct electricity and ions aroused the interest of researchers at the Center for Research and Development of Functional Materials (CDFM), one of the Research, Innovation and Dissemination Centers (RIDCs) funded by FAPESP.

Findings from CDFM’s research in this area were presented by Carlos Frederico de Oliveira Graeff from São Paulo State University’s School of Sciences (FC-UNESP) at FAPESP Week Barcelona, held by FAPESP in partnership with Research Centres of Catalonia (CERCA) on May 28-29 in Barcelona.

Thanks to its electrical properties, scientists believe melanin can serve as a basis for the development of a series of new biologically compatible electronic components, mainly for healthcare applications, such as medical sensors or treatment to stimulate the healing of living tissue, for example.

“Melanin is a natural organic semiconductor,” Graeff said. “It’s a very complex material from the structural standpoint because it isn’t man-made. The main experimental difficulty is investigating the relationships between its structure and properties, which is what materials science considers fundamental for the advancement of knowledge in the area. Without this structural understanding, it’s impossible to establish links with the desired properties.”

In order to characterize the structure of melanin and investigate the links between this structure and the material’s bioelectronic properties, the researchers combined electronic structure calculations with electron spin resonance (ESR), an experimental technique used to study free radicals and detect flaws in materials.

“We set out to show at the molecular level which structures are responsible for the experimental responses,” he said. “What we found was that some centres do account for these characteristics.”

Graeff also led the project “New materials and methods applied to (bio)medicine”. Supported by a Thematic Grant from FAPESP, this project developed three devices: a nitric oxide sensor and two dosimeters, one based on conductive polymers and the other on alanine for use in special radiosurgery techniques, for example.

OLED displays

Graeff also spoke about research on materials that unlike melanin already have commercial applications, such as organic light-emitting diodes (OLEDs).

OLEDs are the most advanced display technology. OLED screens consume less power than LCD, plasma and LED screens, as well as being thinner and lighter, offering a wider viewing angle and displaying more natural colours. Some cell phones already have OLED touch screens.

The researchers studied how the material degrades. “When you buy any product, you want it to last a long time, but equipment of any kind suffers wear and tear, of course. Eventually its performance deteriorates as a result. Our research showed empirically that a degradation mechanism proposed for this type of molecule does indeed exist,” Graeff said.

Another commercial application presented at the event was a nanotechnology hair dryer that combats bacteria and fungi developed by Nanox, a spinoff set up by research groups affiliated with the RIDC.

“Applications of nanotechnology cut across all knowledge areas. The sharing of results and observations in this field contributed to an even better understanding and could drive more applications,” Graeff said about the discussions at FAPESP Week Barcelona.

Antennas

The Catalan experiences with nanotechnology shared at the event included the development of a device called “antenna in a box”, which can detect and sense individual biomolecules via fluorescence with unprecedented resolution and sensitivity.

Developed by researchers at the Photonic Science Institute (ICFO), a member of CERCA, and the Catalan Research & Advanced Studies Institute (ICREA), the technology realises a gain of four orders of magnitude compared to classical microscopes, offering a highly efficient platform for nanoscale biochemical assays.

“One of the ultimate goals of molecular biology is to watch how single molecules work under physiological conditions. New nanotechnology and photonics tools need to be introduced in order to reach ultra-small detection volumes and turn single molecules into bright light sources. Countless applications are possible. Photonics is about light, and light is everywhere,” said Niek Van Hulst, Group Leader at ICFO.

The institute has produced innovations in optical microscopy, plasmonics, solar cells, ultrathin film electrodes, graphene optoelectronics, advanced laser systems, and compact monitors and sensors for use in hostile environments, among others.