Microsensor based on NASICON for the analysis of Na+ in the gingival fluid

A miniaturized electrochemical sensor for in vivo determination of Na+ in the gingival fluid is described. The device includes a NASICON type ceramic as the ion-sensitive membrane and a polyethylene-oxide-based polymer as the internal reference system. The device was successfully used for the direct determination of Na+ activity in gingival fluid. The response time was as short as 10 s. Measurements were performed with an external miniaturized calomel electrode located in the vestibular cavity. Some tests were also performed with an integrated Ag–AgCl electrode. The recordings clearly demonstrate that such a Na+ probe can be used to make in vivo diagnosis.