Researchers Work on Prospective Usage of Biosynthetic Melanin in Bioelectronics

Sometimes known as the next medical frontier, bioelectronics is a research area integrating biology with electronics to develop miniaturized implantable devices with the potential to alter and control electrical signals in the human body.

Large corporations are increasingly interested: for instance, recently, pharmaceutical giant GlaxoSmithKline (GSK) and Alphabet (Google’s parent company) have announced a joint venture in this field.

One of the main difficulties faced by researchers in synthesizing bioelectronic devices is to identify and discover way of using materials that conduct electrons as well as ions, because most communication and other processes in the human body involve ionic biosignals, such as neurotransmitters. Additionally, the materials should be biocompatible.

Overcoming this challenge is the research goal for scientists at São Paulo State University’s School of Sciences (FC-UNESP), Bauru, Brazil. They have been successful in discovering an innovative method to more rapidly synthesize and enabling the use of melanin in miniaturized implantable devices, e.g. biosensors.

Melanin is a polymeric compound responsible for pigmenting the hair, eyes, and skin of mammals, and is regarded as the most promising materials for use in miniaturized implantable devices.

All the materials that have been tested to date for applications in bioelectronics are entirely synthetic. One of the great advantages of melanin is that it’s a totally natural compound and biocompatible with the human body: hence its potential use in electronic devices that interface with brain neurons, for example.

Carlos Frederico de Oliveira Graeff, Professor, UNESP

Graeff explained that one of the main difficulties in using melanin for developing bioelectronic devices is the fact that in contrast to other carbon-based materials (e.g. graphene), melanin does not get easily dispersed in an aqueous medium. This property is the main reason that inhibits its usage in thin-film production.

In addition, the traditional melanin synthesizing process is highly complex because it may take up to 56 days, many steps are highly difficult to control, and it may lead to disorderly structures.

By carrying out successive research work in recent years at the Center for Research and Development of Functional Materials (CDFM), a Research, Innovation and Dissemination Center (RIDC) funded by the São Paulo Research Foundation (FAPESP),

Graeff (a leading researcher at the Center) and his colleagues employed an innovative synthesis technique to acquire biosynthetic melanin with a strong resemblance to natural melanin and better dispersion in water.

The procedure developed by the team is based on changes in parameters - such as temperature and applying oxygen pressure to initiate oxidation of the material - and takes only a few hours to perform.

The application of oxygen pressure enabled the researchers to increase the density of carboxyl groups - organic functional groups comprising of a carbon atom single bonded to a hydroxyl group (oxygen + hydrogen) and double bonded to an oxygen atom. This improves the solubility and enabling the suspension of biosynthetic melanin in water.

The production of thin films of melanin with high homogeneity and quality is made far easier by these characteristics.

Carlos Frederico de Oliveira Graeff, Professor, UNESP

The increase in the density of carboxyl groups enabled the researchers to also synthesize biosynthetic melanin that was more similar to the biological compound.

In living organisms, an enzyme that takes part in the synthesis of melanin enables the synthesis of carboxylic acids.

The innovative melanin synthesis technique allowed the researchers to chemically simulate the role of the enzyme while increasing the density of the carboxyl group.

We’ve succeeded in obtaining a material that’s very close to biological melanin by chemical synthesis and in producing high-quality film for use in bioelectronic devices.

Carlos Frederico de Oliveira Graeff, Professor, UNESP

The Brazilian researchers, working in collaboration with colleagues at research institutions in Canada, have started to use the material in a range of applications such as pH sensors, electrical contacts, and photovoltaic cells.

More recently, the researchers have started attempts toward developing a transistor - a semiconductor device for amplifying or switching electrical power and electronic signals.

Above all, we aim to produce transistors precisely in order to enhance this coupling of electronics with biological systems.

Carlos Frederico de Oliveira Graeff, Professor, UNESP