Electrical pulses speed up nerve regeneration in rats

Biodegradable device delivers electrical stimulation to peripheral nerves to kick start nerve regrowth and enhance muscle recovery

Original source: Physics World

Pain, tingling and numbness in the hands, legs and arms are common symptoms of peripheral nerve injuries. Typically caused by trauma or acute compression, they are considered a significant problem for public health, making up 2-5% of all trauma cases.

Researchers at Washington University School of Medicine in St Louis and Northwestern University have developed an implantable device that can deliver scheduled electrical stimulation to targeted peripheral nerves after surgery has been completed. Their research, published in Nature Medicine, has shown that these electrical pulses help with the nerve regrowth and enhanced muscle recovery in rats.

Wilson RayJohn Rogers and their colleagues wrapped a wireless, biodegradable device around the injured nerve and inserted it into rats with peripheral nerve damage. They programmed the device to deliver electrical pulses at intervals for about two weeks before the device was naturally absorbed into the body.

Currently there is little that can be done to speed up the rate of recovery from nerve injuries. Patients may use physical therapies and pain killers to aid healing, and much of current research focuses on pharmacological approaches such as the application of growth factors and immunosuppressants to stimulate injured nerves. However these studies have had mixed results.

For severe cases, which require surgery, electrical stimulation is applied to the injured nerves as it has been shown to enhance recovery. Electrical stimulation activates the release of proteins promoting nerve regrowth, enhancing the ability of nerve cells to regrow quickly. However, this stimulation only occurs during surgery, and once surgery has finished, the ability to provide electrical stimulation to the nerve ends. The novel method described here is unique in achieving positive results post-surgery.

An example of transient engineered technologies

The device is entirely biocompatible and bioresorbable comprised of a radio frequency power harvester, and an electrical interface, which connects to a targeted nerve. The harvester makes use of a silicon nanomembrane radio frequency diode in addition to a Mg/SiO2/Mg capacitor, a PLGA substrate and an inductor. When radio frequency is passed through the transmission antenna, electrical stimulation is delivered to injured sciatic nerves in rats. The researchers provided one hour per day of stimulation for one, three and six days and a control of no stimulation at all. The recovery was measured over the following ten days. In all cases, any electrical stimulation was better than none at all, improving the muscle mass and strength. The study also found that the more days of applied electrical stimulation, the quicker the improvement in muscle strength and nerve signalling.

This transient electronic device disappears into the body after treatment has been completed, negating the need to put patients through a second operation to remove the device. The bioresorbability of the device provides a unique ability to deliver electrical stimulation before dissolving and leaving the body without a trace.

The researchers have successfully varied the thickness and the composition of materials in the device to tailor its disintegration into the body. These features enable the device to deliver electrical stimulation to patients in ‘doses’ over days or weeks after the surgery depending on the needs of patients. The researchers envisage that devices using transient engineered technologies could one day provide an alternative to compliment pharmaceutical treatments for conditions in humans. This enables the researchers to carry out exciting further work in determining the optimal parameters for regeneration and functional recovery of the peripheral nerves.