Nanotubes Make Implantable, Injectable Sensors
Body sensors are becoming more common, from external fitness trackers that monitor blood flow, motion, temperature, heart rate to biohacked devices embedded under the skin that send text messages when something is awry.
A team of researchers is working on injectable and embeddable sensors made from carbon nanotubes that can be programmed to monitor health conditions as well as environmental changes and can stay in a person’s body for up to a year.
The devices could keep check on a range of bodily functions, such as blood sugar levels and inflammation, as well as alert a person if external air quality has been compromised by pollution, dangerous gases or even poison.
The nanotube sensors were invented by MIT chemical engineering researcher Nicole Iverson. She and her team demonstrated the sensor in mice and published the results in Nature Nanotechnology
Nanotubes are a great choice for these sensors because they can be designed to glow under infrared light when they come into contact with certain chemicals.
To make her sensors, Iverson wrapped carbon nanotubes in DNA sensitive to nitric oxide (NO), which many types of cells use to signal each other. From there she made two types of sensors: an injectable one for short-term monitoring of problems such as a reaction during surgery, and an implanted sensor for long-term monitoring of problems such as cancer, diabetes or immune reactions to artificial joints.
For the injectable sensor, Iverson attached a polymer to the DNA-wrapped nanotubes, which kept them from clumping together in the blood and flowing easily through the lungs and heart, without causing any damage. Most of the nanotubes accumulated in the livers of the test mice.
Once the nanotubes were in the liver, the scientists opened up the mouse’s abdomen and shone a near-infrared laser light onto the organ. The nanotubes lit up (in the infrared), indicating the presence of nitric oxide. Cells use nitric oxide to signal that there is inflammation somewhere in the area. Nanotubes adapted to other chemicals could tell future physicians if there was a tumor present.
The other sensor Iverson developed was made of nanotubes embedded in a gel, which was implanted in a mouse. The researchers activated it with an infrared laser beam — infrared light can penetrate thin layers of tissue. The nanotubes lit up, showing the presence of NO, indicating inflammation also. In the mice, the sensors kept working for 400 days.
The next step will be to link the nanotube sensor to an actual medical device. One idea is to use the nanotubes to signal an insulin pump. The nanotube sensor would be implanted under a person’s skin, detecting glucose levels in the blood. The nanotubes would fluoresce when exposed to certain levels of glucose, and the light could signal the pump to start working and release insulin.
Credit: Bryce Vickmark / MIT