A Biodegradable Device for Electrical Stimulation of Nerve Regrowth

Living tissue has an electromagnetic component to its operation, both at the very small scale inside cellular processes, but also at the larger scale of signaling through the nervous system. I would say that beyond a few well established lines of research and development, such as work on pacemakers or direct stimulation of nerves, the manipulation of electromagnetic fields and currents for therapeutic effect is far from being a mature area of the life sciences. If one roves the literature in search of connections between electromagnetism, regeneration, and metabolism, there are many small interesting areas of study, a few papers here and a few papers there, but nothing that approaches the breadth and funding of, say, any given field under the broad umbrella of small molecule drug development. Perhaps this indicates a comparative lack of potential. Alternatively, perhaps it indicates that modern materials science and biotechnologies are a requirement to proceed effectively, and thus the field is by necessity still young.

The most advanced lines of work in this corner of the life science community are those involving forms of direct electrical stimulation of tissues, often in attempts to mimic natural electrical currents in the body. In these places in our physiology comparatively crude approaches can achieve results that are useful enough to build into therapies. Consider pacemakers, for example, or deep brain stimulation. While modern examples are increasingly subtle and reliable, benefits nonetheless result from electrical stimulation in absence of a complete understanding of what that stimulation does to cellular metabolism. The same sort of paradigm operates for research groups working on the electrical stimulation of damaged nerves; the ability to produce benefits for patients is somewhat ahead of the understanding of what exactly is going on under the hood in terms of cellular activity and signaling. It does tend to make progress more a matter of trial and error than it might otherwise be, but progress is progress; it should all be welcomed.

Implantable, biodegradable devices speed nerve regeneration in rats

Researchers have developed an implantable, biodegradable device that delivers regular pulses of electricity to damaged peripheral nerves in rats, helping the animals regrow nerves in their legs and recover their nerve function and muscle strength more quickly. The size of a quarter, the device lasts about two weeks before being completely absorbed into the body. "We know that electrical stimulation during surgery helps, but once the surgery is over, the window for intervening is closed. With this device, we've shown that electrical stimulation given on a scheduled basis can further enhance nerve recovery. This and other platforms represent the first examples of a 'bioresorbable electronic medicine' - engineered systems that provide active, therapeutic function in a programmable, dosed format and then naturally disappear into the body, without a trace."

The researchers studied rats with injured sciatic nerves. This nerve sends signals up and down the legs and controls the hamstrings and muscles of the lower legs and feet. They used the device to provide one hour per day of electrical stimulation to the rats for one, three or six days, or no electrical stimulation at all, and then monitored their recovery for the next 10 weeks. Any electrical stimulation was better than none at all at helping the rats recover muscle mass and muscle strength. In addition, the more days of electrical stimulation the rats received, the more quickly and thoroughly they recovered nerve signaling and muscle strength. "Before we did this study, we weren't sure that longer stimulation would make a difference, and now that we know it does we can start trying to find the ideal time frame to maximize recovery. Had we delivered electrical stimulation for 12 days instead of six, would there have been more therapeutic benefit? Maybe. We're looking into that now."

Wireless bioresorbable electronic system enables sustained nonpharmacological neuroregenerative therapy

Peripheral nerve injuries represent a significant problem in public health, constituting 2-5% of all trauma cases1. For severe nerve injuries, even advanced forms of clinical intervention often lead to incomplete and unsatisfactory motor and/or sensory function. Numerous studies report the potential of pharmacological approaches (for example, growth factors, immunosuppressants) to accelerate and enhance nerve regeneration in rodent models. Unfortunately, few have had a positive impact in clinical practice.

Direct intraoperative electrical stimulation of injured nerve tissue proximal to the site of repair has been demonstrated to enhance and accelerate functional recovery, suggesting a novel nonpharmacological, bioelectric form of therapy that could complement existing surgical approaches. A significant limitation of this technique is that existing protocols are constrained to intraoperative use and limited therapeutic benefits. Herein we introduce (i) a platform for wireless, programmable electrical peripheral nerve stimulation, built with a collection of circuit elements and substrates that are entirely bioresorbable and biocompatible, and (ii) the first reported demonstration of enhanced neuroregeneration and functional recovery in rodent models as a result of multiple episodes of electrical stimulation of injured nervous tissue.

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