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Implantable sensor to enable long-term medical monitoring

Posted: 07 Nov 2013 ?? ?Print Version ?Bookmark and Share

Keywords:MIT? implantable sensor? nitric oxide? carbon nanotube?

To make the particles injectable, Iverson attached PEG, a biocompatible polymer that inhibits particle-clumping in the bloodstream. She found that when injected into mice, the particles can flow through the lungs and heart without causing any damage. Most of the particles accumulate in the liver, where they can be used to monitor NO associated with inflammation.

"So far we have only looked at the liver, but we do see that it stays in the bloodstream and goes to kidneys. Potentially we could study all different areas of the body with this injectable nanoparticle," Iverson says.

The longer-term sensor consists of nanotubes embedded in a gel made from alginate, a polymer found in algae. Once this gel is implanted under the skin of the mice, it stays in place and remains functional for 400 days. The researchers believe it could last even longer. This kind of sensor could be used to monitor cancer or other inflammatory diseases, or to detect immune reactions in patients with artificial hips or other implanted devices, according to the researchers.

Once the sensors are in the body, the researchers shine a near-infrared laser on them, producing a near-infrared fluorescent signal that can be read using an instrument that can tell the difference between nanotubes and other background fluorescence.

The new sensors creatively merge the fields of chemistry, polymers, nanomaterials, biology, medicine, and optics, said James Tour, a professor of chemistry at Rice University's Smalley Institute for Nanoscale Science and Technology who was not part of the research team. "The selectivity and sensitivity are indeed impressive."

The research was funded by a grant from Sanofi-Aventis, and also partly by the National Institutes of Health, the National Cancer Institute, the National Institute of Environmental Health Sciences, a Beckman Young Investigator Award and the National Science Foundation.

Iverson is now working on adapting the technology to detect glucose, by wrapping different kinds of molecules around the nanotubes.

Most diabetic patients must prick their fingers several times a day to take blood glucose readings. While there are electrochemical glucose sensors available that can be attached to the skin, those sensors last only a week at most, and there is a risk of infection because the electrode pierces the skin.

Furthermore, Strano said, the electrochemical sensor technology is not accurate enough to be incorporated into the kind of closed-loop monitoring system that scientists are now working towards. This type of system would consist of a sensor that offers real-time glucose monitoring, connected to an insulin pump that would deliver insulin when needed, with no need for finger pricking or insulin injection by the patient.

"The current thinking is that every part of the closed-loop system is in place except for an accurate and stable sensor. There is considerable opportunity to improve upon devices that are now on the market so that a complete system can be realised," Strano added.


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