D.eep’s brain stimulation therapies have proven to be an invaluable treatment option for patients suffering from debilitating diseases such as Parkinson’s. However, it, and its sister technology, brain computer interfaces, currently suffer from a critical shortcoming: The electrodes that convert pulsed electrons into bioelectric signals do not adapt well to surrounding brain tissue. And that’s where the people in lab coats and holding squids come in! In We Are Electric: Inside the 200-Year Search for Our Body’s Bioelectric Code and What the Future Holds, Author Sally Adee delves into two centuries of research into an often misunderstood and maligned branch of scientific discovery, guiding readers from the pioneering works of Alessandro Volta to the life-saving applications that could be possible once scientists doctors learn to communicate directly with the cells of our body.
Hachette Books
Taken from We Are Electric: Inside the 200-Year Search 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.
Lost in translation
“There is a fundamental asymmetry between the devices that drive our information economy and the tissues of the nervous system,” Bettinger said. the edge in 2018. “Your cell phone and your computer use electrons and pass them back and forth as the fundamental unit of information. However, neurons use ions such as sodium and potassium. This is important because, to make a simple analogy, that means you need to translate the language.”
“One of the misnomers in the field is actually that I am injecting current through these electrodes,” explains Kip Ludwig. “No, if I’m doing it right, I don’t.” The electrons that travel through a platinum or titanium wire to the implant never reach the brain tissue. Instead, they line up on the electrode. This produces a negative charge, which draws ions from the neurons around it. “If I get enough ions out of the tissue, I cause voltage-gated ion channels to open,” says Ludwig. That can, but not always, cause a nerve to fire an action potential. Put your nerves on 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 just work to try to write our own action potentials over those of the brain? The problem is that our attempts to write action potentials can be incredibly clumsy, says Ludwig. They don’t always do what we think they do. For one, our tools aren’t precise enough to hit only the exact neurons we’re trying to stimulate. The implant then finds itself in the middle of a group of different cells, sweeping up and activating unrelated neurons with its electrical field. Remember how I said that glia were traditionally considered to be the cleaning staff of the brain? Well, more recently it emerged that they also process some information, and our clumsy electrodes will fire those too, with unknown effects. “It’s like pulling the plug on the bathtub and trying to move just one of three toy boats in the bathwater,” says Ludwig. And even if we do manage to hit the neurons we’re targeting, there’s no guarantee that the stimulation is hitting the right location.
To bring electroceuticals to medicine, we really need better techniques for talking to cells. If the electron-ion language barrier is an obstacle to talking to neurons, it’s absolutely impossible for cells that don’t use action potentials, like the ones we’re trying to target with next-generation electrical interventions, including cells from the skin, bone cells and the rest. If we want to control the membrane voltage of cancer cells to convince them to return to their normal behavior; if we want to push the wound current in skin or bone cells; if we want to control the fate of a stem cell, none of that can be accomplished with our single tool of making a nerve fire an action potential. We need a bigger set of tools. Fortunately, this is the goal of a rapidly growing area of research that seeks to make devices, computing elements, and wiring that can speak their native language with ions.
Several research groups are working on “mixed driving,” a project whose goal is devices that can speak bioelectricity. It relies heavily on advanced plastics and polymers with long names that often include punctuation and numbers. If the goal is a DBS electrode that can remain 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 now. And that search is far from over. People are understandably starting to wonder: why not just skip the middleman and actually do this with bio-based materials instead of making polymers? Why not learn how nature does it?
It has been tried before. In the 1970s, there was great interest in using coral for bone grafts instead of autografts. Instead of double traumatic surgery to harvest the necessary bone tissue from a different part of the body, the coral implants acted as a scaffold to allow the body’s new bone cells to grow and form the new bone. Coral is naturally osteoconductive, which means that new bone cells happily glide over it and find a nice place to proliferate. It’s also biodegradable: after the bone grew on it, the coral was gradually absorbed, metabolized, and then excreted from the body. Steady improvements have produced few inflammatory responses or complications. There are now several companies that grow specialized coral for bone grafts and implants.
After the success of the coral, people began to take a closer look at marine sources of biomaterials. This field is now rapidly evolving: thanks to new processing methods that have made it possible to harvest vast amounts of useful materials from what used to be just marine debris, the last decade has seen an increasing number of biomaterials originating 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 these has increased is the effort to move away from polluting synthetic plastic materials.
In addition to all the other benefits of marine-sourced duplicates, they can also conduct 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 out of a piece of squid.
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