Image of Implantable Sensor.
An implantable sensor has the speed and precision for tracking a brain chemical known to be elevated in certain brain diseases and after a spinal cord injury. (Credit: Purdue University image/Tran Nguyen)

Engineers have built a tiny, flexible sensor that is faster and more precise than past attempts at tracking a chemical associated with nasty migraines. The sensor, an implantable device on the spinal cord, is primarily a research tool for testing in animal models but could find future clinical use as a way to monitor whether a drug for neurotrauma or brain disease is working.

Damaged nerve structures mean that loads of glutamate leak out into spaces outside of cells, over-exciting and damaging them. Brain diseases, including Alzheimer's and Parkinson's, also show elevated levels of glutamate.

Researchers are addressing these issues through implantable sensors that they have 3D printed and laser-micromachined — processes that are already used regularly in the lab and industry. The technique allows researchers to rapidly change the size, shape, and orientation of the sensors and then test in animal models without having to go through the more expensive process of microfabrication. Measuring levels in vivo would help researchers to study how spinal cord injuries happen, as well as how brain diseases develop.

The researchers implanted the device into the spinal cord of an animal model and then injured the cord to observe a spike. The device captured the spike immediately, whereas for current devices, researchers have had to wait 30 minutes to get data after damaging the spinal cord.

In the future, the researchers plan to create a way for the biosensors to self-clear of inflammatory cells that the body recruits to protect itself. These cells typically form a fibrous capsule around the biosensor, which blocks its sensitivity. The technology could also allow for implanting more sensors along the spinal cord, which would help researchers to know how far glutamate spreads and how quickly.