A sensor to be injected into the skin just like a tattoo that measures sodium concentrations in the blood has been developed by US scientists. The sensor could be used to monitor diseases or warn against dangerously low sodium levels during exercise.
Heather Clark from Northeastern University, Boston, and coworkers made plastic nanobeads that fluoresce to different extents with changes in sodium levels. The beads are coated with a biocompatible polymer and are injected just under the skin to allow the fluorescence to be monitored easily.
Technology for determining the amount of sodium in the bloodstream has been available for some time. However, it requires a blood sample from the patient, which limits the measurements to isolated time points. This is a problem for understanding a condition called hyponatremia, where sodium concentrations in blood serum are lower than normal. Hyponatremia can occur after certain types of surgery, with brain trauma or tumours, and has been found in endurance athletes.
Link to journal article
In vivo sodium concentration continuously monitored with fluorescent sensors
J. Matthew Dubach, Edward Lim, Ning Zhang, Kevin P. Francis and Heather Clark
Integr. Biol., 2011, DOI: 10.1039/c0ib00020e