Silicone sensors monitor the brain then dissolve

Tiny implants measure intracranial pressure and temperature before being absorbed into the body

Wireless brain sensors developed by researchers at Washington University School of Medicine in St. Louis and the University of Illinois at Urbana-Champaign are smaller than a pencil tip and monitor intracranial pressure and temperature before being absorbed by the body.

The devices are made mainly of polylactic-co-glycolic acid (PLGA) and silicone, and they can transmit accurate pressure and temperature readings, as well as other information.

Washington University said that the implants could be used to monitor patients with traumatic brain injuries but the researchers said they believe they can build similar absorbable sensors to monitor activity in organ systems throughout the body.

The findings have been published in the journal, Nature and was co-authored by Rory Murphy, a neurosurgery resident at Washington University School of Medicine and Barnes-Jewish Hospital in St. Louis and Wilson Ray, assistant professor of neurological and orthopaedic surgery at Washington University.

Murphy said: “Electronic devices and their biomedical applications are advancing rapidly but a major hurdle has been that implants placed in the body often trigger an immune response, which can be problematic for patients.

“The benefit of these new devices is that they dissolve over time, so you don’t have something in the body for a long time period, increasing the risk of infection, chronic inflammation and even erosion through the skin or the organ in which it’s placed.

“Plus, using resorbable devices negates the need for surgery to retrieve them, which further lessens the risk of infection and further complications.”

Murphy collaborated with engineers in the laboratory of John Rogers, a professor of materials science and engineering at the University of Illinois, to build the sensors.

Rogers said: “With advanced materials and device designs, we demonstrated that it is possible to create electronic implants that offer high performance and clinically relevant operation in hardware that completely resorbs into the body after the relevant functions are no longer needed. This type of bio-electric medicine has great potential in many areas of clinical care.”

The researchers tested the sensors in baths of saline solution that caused them to dissolve after a few days. Next, they tested the devices in the brains of laboratory rats and are now planning to test the technology in patients.

In patients with traumatic brain injuries, neurosurgeons attempt to decrease the pressure inside the skull using medications. If pressure cannot be reduced sufficiently, patients often undergo surgery.

The new devices could be placed into the brain at multiple locations during such operations, according to Washington University.

Murphy said: “The ultimate strategy is to have a device that you can place in the brain — or in other organs in the body — that is entirely implanted, intimately connected with the organ you want to monitor and can transmit signals wirelessly to provide information on the health of that organ, allowing doctors to intervene if necessary to prevent bigger problems.

“And then after the critical period that you actually want to monitor, it will dissolve away and disappear.”