Dissolving brain implant

A dissolving brain implant, which could revolutionise the monitoring of traumatic brain injuries, has been announced this week. In recent years we've seen increasing use of small, implanted electronic devices designed to monitor signs and symptoms in patients, or deliver drugs. But these implants often need to be removed surgically when they're no longer needed. Now US scientist John Rogers, from the University of Illinois, has come up with a "soluble" alternative, as he explains to Kat Arney...

John - The particular device that we've reported in this current publication is designed to meet a current clinical need in the treatment of patients who suffer from severe traumatic brain injury and, in particular, to monitor their recovery process.  So, it goes into the intracranial space to measure pressure and temperature because those two parameters are very important for a physician to track because, if they fall outside an error window, it could have profound negative consequences for the patient.

Kat - So you've basically built this tiny, wireless implant that goes in someone's brain.  Does it completely vanish again when it's not needed?

John - Yes, completely goes away, entirely.  You know, how do you do this? And it's a multi-material system, each one of which individually is soluble in biofluids to biocompatible end products.  So magnesium, for example, is biocompatible; magnesium peroxide is a result of the dissolution of magnesium in biofluids; magnesium is part of a recommended daily diet - you find it in multivitamins, so we go through the list and we've been able to identify a full compliment of materials needed to do this.  The clinical relevance, in terms of function, is during that critical recovery period when the patient is at highest risk for high pressure or high temperature.  So the front end of that is about a week, so we've designed our devices to operate stably and reliably over that timeframe and then slowly degrade on a less critical timeframe that's typically two to three months.

Kat - Although this is a device that does dissolve so you don't have to take it out again, presumably you have to get it in.  How do you get it into patients in the first place?

John - Well that's a good question.  I mean the utility of these kind of intracranial monitors, even the non-resorbable ones that are used today, are typically most important in pretty severe traumatic brain injury cases.  We're not talking about people that come into the hospital and have bumped their head.  These are traumatic events and, in most cases, the sensors can be inserted at the tailend of a surgical procedure that needs to happen any way so the intracranial space is open for that purpose, and the device is just slipped in at the final step at that intervention.  If the skull is not opened in that context then what people do today is they create small burr holes through the skull and inset the device, so their miniaturization becomes an important  aspect of the device design because you want to minimise the impact on the patient getting it in.  So, in that sense, the physics of the way that our devices work are compatible with downscaling, even to a further degree than we've demonstrated in this paper.  The device is about the size of a grain of rice but they could be much smaller.

Kat - Could this kind of technology be used for anything else, not just monitoring signs and symptoms in patients?

John - Yes, I think there are a lot of other functions that could be interesting, for example, going beyond just sensing and monitoring to stimulation and intervention.  So we have parallel work, as an example, resorbable devices that do electrical stimulation of the peripheral nervous system and, if you look at the healing of peripheral nerves, there's data in the literature that if you stimulate electrically that damaged site, in an appropriate way, you can actually, significantly accelerate the healing process.  And then once the nerve is healed and you don't need the device any more, so you'd just engineer it to just dissolve away.