Tag Archives: biocompatible implants

Cyborgs based on melanin circuits

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Pigments for biocompatible electronics? According to a March 26, 2019 news item on Nanowerk this is a distinct possibility (Note: A link has been removed),

The dark brown melanin pigment, eumelanin, colors hair and eyes, and protects our skin from sun damage. It has also long been known to conduct electricity, but too little for any useful application – until now.

In a landmark study published in Frontiers in Chemistry (“Evidence of Unprecedented High Electronic Conductivity in Mammalian Pigment Based Eumelanin Thin Films After Thermal Annealing in Vacuum”), Italian researchers subtly modified the structure of eumelanin by heating it in a vacuum.

“Our process produced a billion-fold increase in the electrical conductivity of eumelanin,” say study senior authors Dr. Alessandro Pezzella of University of Naples Federico II and Dr. Paolo Tassini of Italian National Agency for New Technologies, Energy and Sustainable Economic Development. “This makes possible the long-anticipated design of melanin-based electronics, which can be used for implanted devices due to the pigment’s biocompatibility.”

This is a rather dreamy image to illustrate the point,

Despite extensive research on the structure of melanin, nobody has yet managed to harness its potential in implantable electronics. Image: Shutterstock. [downloaded from https://blog.frontiersin.org/2019/03/26/will-cyborgs-circuits-be-made-from-melanin/]

A March 26, 2019 Frontiers in Chemistry (journal) press release (also on EurekAlert), which originated the news item, expands on the theme,

A young Pezzella had not even begun school when scientists first discovered that a type of melanin can conduct electricity. Excitement quickly rose around the discovery because eumelanin – the dark brown pigment found in hair, skin and eyes – is fully biocompatible.

“Melanins occur naturally in virtually all forms of life. They are non-toxic and do not elicit an immune reaction,” explains Pezzella. “Out in the environment, they are also completely biodegradable.”

Decades later, and despite extensive research on the structure of melanin, nobody has managed to harness its potential in implantable electronics.

“To date, conductivity of synthetic as well as natural eumelanin has been far too low for valuable applications,” he adds.

Some researchers tried to increase the conductivity of eumelanin by combining it with metals, or super-heating it into a graphene-like material – but what they were left with was not truly the biocompatible conducting material promised.

Determined to find the real deal, the Neapolitan group considered the structure of eumelanin.

“All of the chemical and physical analyses of eumelanin paint the same picture – of electron-sharing molecular sheets, stacked messily together. The answer seemed obvious: neaten the stacks and align the sheets, so they can all share electrons – then the electricity will flow.”

…

This process, called annealing, is used already to increase electrical conductivity and other properties in materials such as metals.

For the first time, the researchers put films of synthetic eumelanin through an annealing process under high vacuum to neaten them up – a little like hair straightening, but with only the pigment.

“We heated these eumelanin films – no thicker than a bacterium – under vacuum conditions, from 30 min up to 6 hours,” describes Tassini. “We call the resulting material High Vacuum Annealed Eumelanin, HVAE.”

The annealing worked wonders for eumelanin: the films slimmed down by more than half, and picked up quite a tan.

“The HVAE films were now dark brown and about as thick as a virus,” Tassini reports.

Crucially, the films had not simply been burnt to a crisp.

“All our various analyses agree that these changes reflect reorganization of eumelanin molecules from a random orientation to a uniform, electron-sharing stack. The annealing temperatures were too low to break up the eumelanin, and we detected no combustion to elemental carbon.”

…

Having achieved the intended structural changes to eumelanin, the researchers proved their hypothesis in spectacular fashion.

“The conductivity of the films increased billion-fold to an unprecedented value of over 300 S/cm, after annealing at 600°C for 2 hours,” Pezzella confirms.

Although well short of most metal conductors – copper has a conductivity of around 6 x 107 S/cm – this finding launches eumelanin well into a useful range for bioelectronics.

What’s more, the conductivity of HVAE was tunable according to the annealing conditions.

“The conductivity of the films increased with increasing temperature, from 1000-fold at 200°C. This opens the possibility of tailoring eumelanin for a wide range of applications in organic electronics and bioelectronics. It also strongly supports the conclusion from structural analysis that annealing reorganized the films, rather than burning them.”

There is one potential dampener: immersion of the films in water results in a marked decrease in conductivity.

“This contrasts with untreated eumelanin which, albeit in a much lower range, becomes more conductive with hydration (humidity) because it conducts electricity via ions as well as electrons. Further research is needed to fully understand the ionic vs. electronic contributions in eumelanin conductivity, which could be key to how eumelanin is used practically in implantable electronics.” concludes Pezzella.

Here’s a link to and a citation for the paper,

Evidence of Unprecedented High Electronic Conductivity in Mammalian Pigment Based Eumelanin Thin Films After Thermal Annealing in Vacuum by Ludovico Migliaccio, Paola Manini, Davide Altamura, Cinzia Giannini, Paolo Tassini, Maria Grazia Maglione, Carla Minarini, and Alessandro Pezzella. Front. Chem., 26 March 2019 DOI: https://doi.org/10.3389/fchem.2019.00162

This paper is open access.

The shrimp will save us

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Who knew that ceramics are a preferred material for body armour? Clearly, not me. According to the June 13, 2012 news item on Nanowerk, there’s a shrimp whose shell may offer inspiration for better quality ceramics used not only in military body armour but also in joint replacements. Here’s an image of one type of mantis shrimp,

Flower Mantis Shrimp (Photo Credit Silke Baron)

Pretty, isn’t it? Here’ s more from the June 13, 2012 news item on Nanowerk,

A scientist from Nanyang Technological University (NTU) may be onto an ocean of discovery because of his research into a little sea creature called the mantis shrimp.

The research is likely to lead to making ceramics – today’s preferred material for medical implants and military body armour – many times stronger. These findings were published in last Friday’s Science (“The Stomatopod Dactyl Club: A Formidable Damage-Tolerant Biological Hammer” [behind a paywall]), and focused on the mantis shrimp’s ability to shatter aquarium glass and crab shells alike.

The common creature native to the Indo Pacific, has club-like ‘arms’ which can strike prey at speeds matching that of a 5.56mm rifle bullet. Each impact generates a force exceeding 50 kilograms, which is hundreds of times the mantis shrimp’s weight.

The June 13, 2012 news release from Nanyang Technological University (Singapore) notes,

Assistant Professor Ali Miserez, from NTU’s School of Materials Science Engineering (MSE) and School of Biological Sciences (SBS), collaborated with Dr James Weaver from Harvard University as well as scientists from the University of California-Riverside, Purdue University, and Brookhaven National Laboratory in the United States.

They have observed down to the nanoscale the highly unique composite structure of the mantis shrimp’s club and discovered that it is weaved together in a unique fashion to create a structure tougher than many engineered ceramics. This is the first time that the mantis shrimp’s club is studied in such detail.

“The highly damage resistant property of the mantis shrimp could be most useful in medical products such as hip and joint implants, as they sustain impacts hundreds of times daily during walking and daily activities,” said Asst Prof Miserez, a recipient of the National Research Foundation Fellowship, which provides a research grant of up to S$3 million over five years.

“Damaged hip implants are a real problem, and cost billions of dollars to the healthcare systems worldwide. They also cause painful surgeries to patients when they need to be replaced. Using a nature-inspired blueprint to design biocompatible implants is actually a ‘shrimple‘ solution.”

Thank you for that wordplay. ‘Shrimple’, indeed! More seriously, I have previously commented on hip replacements and the search for ways to improve them, most recently in my April 20, 2012 posting.

The June 13, 2012 news release from Nanyang Technological University goes on to discuss Dr. Miserez’s lab and other applications for the shrimp-inspired ceramic materials,

Designing a damage-resistant implant which is made out of a bio-compatible bone material would solve the above problems [bone loss, toxicity, and immune reactions], as the material exists naturally in the human body. Asst Prof Miserez, whose laboratory is situated at MSE’s Centre for Biomimetic Sensor Science, said they will continue their research to better understand the design and materials and will attempt to replicate it in the laboratory next year.

His team, which includes PhD student Shahrouz Amini, will be focusing on developing a new bio-compatible material which could be used for medical implants such as hip implants. However, the potential applications for these nature-inspired designs are widespread because the final product is expected to be lighter weight and more impact resistant than existing products. These could include new types of armour plating, lighter vehicles and tougher engine and aircraft components like pistons and gears, all of which suffer from impact, wear and abrasion damage over time. [emphasis mine]

Possible medical and military advances march hand in hand, again!