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How a pigment might hold the key to cybernetic implants in humans

A team of scientists working at ISIS Neutron and Muon Source (ISIS) are helping to make science fiction a reality by studying how a humble pigment present in humans and most living things, melanin, could be the key to implanting and integrating electronic devices into the human body.

This month marks the 50th anniversary of the Apollo Moon landing. In 1969, the world watched enraptured as science fiction became reality and humankind took its first tentative steps into the wider universe. Back then, people may have been forgiven for thinking that, by 2019, we’d be living in a utopia in which humans had long-since populated the first Lunar and Martian colonies and those of us still on Earth would travel in flying cars. Robots would walk among us; we’d be well on the way to cracking the problem of faster-than-light travel; and some humans would have become machine-augmented with cybernetic enhancements.

So far, none of these predictions have truly come to pass (although, aside from figuring out the intricacies of warp speed, we have made some progress on most of them). Even the idea of a cybernetics enhancements, or “cyborgs”, is beginning to enter the realm of science fact.  For example, when you consider that people have had electronic devices such as pacemakers and cochlear implants integrated into their bodies for decades, you could argue that cyborgs do already exist. In reality, for the foreseeable future at least, any cybernetic enhancement humankind may undergo will be limited to medical applications.

Sometimes called the next medial frontier, electroceuticals is a research field that seeks to use electronics for a medical outcome. As a result of this medical need, a new fundamental field of research, bioelectronics, is coming of age in which the search is on to combine electronics and biology to develop miniaturised, implantable electronic devices capable of altering and controlling electrical signals in the human body.

On the face of it, getting medical devices and the human body to work together would seem to be a relatively straightforward proposition – after all, both use electric signals to convey information between their constituent parts (whether that be along a circuit board or via nerves and neurons).

Unfortunately, whereas electronic devices use electrons to carry a current, the human body uses charged particles called ions. Essentially, the mechanical and biological systems speak different electrical languages and the challenge is finding a way to get them to talk to each other efficiently and effectively. What is needed is a material that can act as an interface between an electronic device and the ionic human body. As an added complication, it also has to be biocompatible so it won’t be rejected by the body’s immune system.

In recent years, a promising candidate for the role of bio-electronic middle-man has been identified and, rather handily, it is one that is already present in the human body: melanin.

Melanin is the pigment that gives your skin, hair and iris’ their colour and that protects your skin from the damaging effects of the Sun. It also happens to be a natural electrical conductor with excellent material properties, which means it has the potential to be a sought-after electronic and ionic interface. And because melanin occurs naturally in the human body (and, in fact, in virtually all forms of life) it is non-toxic, biodegradable, and does not illicit an immune reaction. As such, melanin is now the subject of great interest by those engaged in electroceutical and bioelectronic research.

To make the best use of melanin though, scientists have to better understand how it carries an electrical charge and how its properties are affected by the warm and wet conditions within the human body. It is these properties that an international team of scientists from Swansea University (from the Sustainable Advanced Materials group), São Paulo State University (UNESP), and the Moscow Institute of Physics and Technology has been investigating at ISIS Neutron and Muon Source (ISIS).

They have been studying a synthetic version of eumelanin, which is the most common form of melanin responsible for brown and black hair colour (it is also what gives squid ink its black colour). Specifically, they have been using two techniques; quasi-elastic neutron scattering and muon spin resonance, to look at how melanin’s major ionic charge carrier, the proton, behaves at different temperatures and levels of hydration.

It is already known that proton conductivity in melanin improves in wet conditions, but the team hope that their measurements will allow them to construct scientific models that will help them to understand how proton conductivity and mobility changes at different temperatures and levels of hydration. This information will be key in designing practical melanin-based implantable electronics.

The team lead, Dr. Bernard Mostert (Marie SkÅ‚odowska-Curie COFUND Fellow at Swansea University’s Chemistry Department), hopes that the research will also lead to better understanding of melanin’s role in medical conditions such as melanoma cancer and Parkinson’s disease. Sufferers of these conditions have high levels of copper and iron ions in their neuromelanin – a melanin form found in the brain stem.

Melanin could be the key to unlocking a new generation of implantable, biocompatible devices and sensors for medicine and medical research. Among the many potential applications are devices for monitoring epileptic fits in real-time that could potentially deliver ‘doses’ of electricity to counteract them; human-computer interfaces for controlling artificial limbs; sensors that study how cells and tissues respond to drugs – the list is extensive and their potential is exciting.

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Last updated: 29 July 2019


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