by Heyeep Brain Stimulation treatments have proven to be an invaluable treatment option for patients suffering from otherwise debilitating diseases such as Parkinson’s. However, it—and its technology’s brain interfaces—currently have a critical drawback: the electrodes that convert the electron pulses into bioelectrical signals don’t mesh well with the surrounding brain tissue. And there come the people in lab coats and holding squids! In We Are Electric: Inside the 200-Year Hunt for Our Body’s Bioelectric Code and What the Future Holds, Author Sally Adee delves into two centuries of research in an often misunderstood and maligned branch of scientific discovery, guiding readers from the groundbreaking works of Alessandro Volta to the life-saving applications that may become possible once doctors learn to communicate directly with the body’s cells us.
Hachette Books
Excerpt from We Are Electric: Inside the 200-Year Hunt for Our Body’s Bioelectric Code and What the Future Holds by Sally Adee. Copyright © 2023. Available from Hachette Books, an imprint of Hachette Book Group, Inc.
It gets lost in translation
“There is a fundamental asymmetry between the devices that drive our information economy and the tissues in the nervous system,” Bettinger said. The lip in 2018. “Your cell phone and your computer use electrons and pass them back and forth as the fundamental unit of information. Neurons, however, use ions such as sodium and potassium. That matters because, to make a simple analogy, that means you have to translate the language.”
“One of the misnomers in the field actually is that I’m injecting current through these electrodes,” explains Kip Ludwig. “Not if I do it right, I don’t.” Electrons traveling down a platinum or titanium wire to the implant never enter your brain tissue. Instead, they line up at the electrode. This produces a negative charge, which draws ions from the neurons around it. “If I pull enough ions away from the tissue, I cause voltage-gated ion channels to open,” says Ludwig. This can – but not always – make nerve fire an actionable possibility. Get nerves for fire. That’s it – that’s your only move.
It may seem counterintuitive: the nervous system works with action potentials, so why wouldn’t it be efficient to just try to write our own action potentials on top of the brain’s potentials? The problem is that our attempts to write action dynamics can be incredibly sketchy, says Ludwig. They don’t always do what we think they do. For one thing, our tools aren’t precise enough to hit only the exact neurons we’re trying to stimulate. So the implant sits in the middle of a bunch of different cells, scanning and activating unrelated neurons with its electric field. Remember how I said that the glia were traditionally thought of as the brain’s guard staff? Well, more recently it has emerged that they also do some information processing – and our clumsy electrodes will trigger them too, with unknown results. “It’s like pulling the plug on your bathtub and trying to move just one of three toy boats in the bathtub water,” says Ludwig. And even if we manage to hit the neurons we’re trying to, there’s no guarantee that the stimulation is hitting it in the right place.
To introduce electrocautery into medicine, we really need better techniques to talk to cells. If the electron-to-ion language barrier is a barrier to talking to neurons, it’s a complete nonstarter for cells that don’t use action potentials, like the ones we’re trying to target with next-generation electrical interventions, like skin cells, bone cells, and the rest. If we want to control the membrane tension of cancer cells to get them to return to their normal behavior. if we want to push the wound current to skin or bone cells. if we want to control the fate of a stem cell – none of this is possible with our one and only tool to make a neural fire an action potential. We need a bigger toolbox. Fortunately, that’s the goal for a rapidly growing area of research that seeks to build devices, computing components and wiring that can speak to ions in their native language.
Several research groups are working on “mixed conductivity,” a project whose goal is devices that can talk about bioelectricity. It relies heavily on plastics and advanced polymers with long names that often include punctuation and numbers. If the goal is a DBS electrode that you can keep in the brain for more than ten years, these materials will need to safely interact with the body’s native tissues for much longer than they do now. And that search is far from over. Understandably, people are starting to wonder: why not cut out the middle man and make this stuff out of bio-based materials instead of building polymers? Why not learn how nature does it?
It has been tried before. In the 1970s, there was a great deal of interest in using coral for bone grafts instead of autografts. Instead of a traumatic double surgery to harvest the necessary bone tissue from a different part of the body, the coral implants acted as a scaffold to let the body’s new bone cells grow and form the new bone. Coral is naturally osteoconductive, which means that new bone cells happily glide over it and find it a pleasant place to proliferate. It is also biodegradable: after the bone grew on it, the coral was gradually absorbed, metabolized and then excreted by the body. Steady improvements have produced few inflammatory responses or complications. There are now several companies cultivating specialized corals for bone grafts and implants.
After the success of corals, people began to look more closely at marine sources for biomaterials. This field is now developing rapidly — thanks to new processing methods that have made it possible to harvest many useful materials from what was simply marine waste, the last decade has seen an increasing number of biomaterials derived from marine organisms. These include replacement sources for gelatin (snails), collagen (jellyfish) and keratin (sponges), marine sources of which are abundant, biocompatible and biodegradable. And not just inside the body – one reason interest in them has grown is the effort to move away from polluting synthetic plastic materials.
Apart from all the other advantages of marine debris, it is also capable of channeling an ion current. That’s what Marco Rolandi was thinking in 2010 when he and his colleagues at the University of Washington built a transistor from a piece of squid.
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