An international team of researchers has developed a miniaturized wireless electronic device that can monitor temperature and pressure when implanted into the brains of mice, and then dissolve to be naturally resorbed into the soft tissue once they are no longer needed.

Electronic implants are used widely in the treatment of numerous medical conditions, ranging from pacemakers and defibrillators given to cardiac patients, electrode arrays used for deep brain stimulation in patients with Parkinson’s Disease, and devices used to monitor intracranial temperature and pressure inside the skulls of people with severe traumatic brain injuries.

Facebook Twitter Pinterest Artist’s rendition of the sensor and wireless transmitter monitoring a rat’s brain. Image: Julie McMahon

Such devices are sometimes used for short periods of time, and often are implanted permanently. But implantation always carries some risk – the devices can be somewhat cumbersome and their wires and metallic components are breeding grounds for bacteria, so the implantation site can become infected. And removing the device, or replacing it if it malfunctions, involves another surgical procedure – and more distress – for the patient.

The new device, developed by a research team that includes engineers, materials scientists, and neurosurgeons in America and South Korea, and described in the journal Nature, could potentially overcome these limitations. It consists of a pressure and temperature sensor, each one smaller than a grain of rice, integrated on a biodegradable silicon chip that sits on the surface of the brain, and connected to a wireless transmitter attached to the outside of the skull.

The researchers tested the device in rats, and showed that it can monitor intracranial pressure, and the temperature changes that occur as the rats drift in and out of consciousness following administration of an anaesthetic, at least as accurately as existing devices. But this device is unique because its components are made from so-called “green electronics” – natural materials that are fully biodegradable and biocompatible, which are designed to work for a few weeks, and then completely dissolve, over the course of about a day, when immersed in watery fluids such as cerebrospinal fluid.

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When they examined the brain tissue afterwards, the researchers found no indication of an inflammatory response, or of scarring around the implantation site, confirming that the device is fully biocompatible. They then modified the device to show that it can also be used to take the same measurements from sites about 5mm below the surface of the rat brain.



The researchers say the device can easily be modified in other ways to monitor other important physiological parameters of brain function, such as acidity and the motion of fluids. It could also be used to deliver drugs to the brain, and, with the incorporation of microelectrodes, to stimulate or record neuronal activity.

As well as being fully biocompatible – and, therefore, safer – the fabrication process is also cheaper and more environmentally-friendly than that used for existing technologies, and the researchers are now aiming to test it in human clinical trials.

Reference

Kang, S. -K., et al. (2016). Bioresorbable silicon electronic sensors for the brain. Nature, DOI: 10.1038/nature16492 [Abstract]