Nitric oxide (NO) carries messages within the brain and coordinates immune system functions. It appears to have contradictory roles in cancer progression, and researchers at MIT in Cambridge, MA, are working to understand this better by creating a new tool to measure it in the body in real time. They have built a sensor that can monitor NO in living animals for more than a year.

The sensors can be implanted under the skin and used to monitor inflammation. This is the first demonstration that nanosensors could be used within the body for this extended period of time.

The sensors, made of carbon nanotubes, could also be adapted to detect other molecules, including glucose, they say. In fact, the team is currently working on sensors that could be implanted under the skin of diabetic patients to monitor their glucose or insulin levels, eliminating the need to take blood samples.

The laboratory at MIT has recently developed carbon nanotube sensors for a variety of molecules, including hydrogen peroxide and toxic agents like the nerve gas sarin. Such sensors take advantage of carbon nanotubes' natural fluorescence, by coupling them to a molecule that binds to a specific target. When the target is bound, the tubes' fluorescence brightens or dims.

The team modified the nanotubes to create two different types of sensors: one that can be injected into the bloodstream for short-term monitoring, and another that is embedded in a gel so it can be implanted long-term under the skin.