Clinical applications of ion selective field effect transistors

Detailed clinical evaluation of the measurement of whole blood sodium and potassium by ion selective field effect transistors (ISFETs) has been undertaken and compared with measurements using ISEs. Comparison of the analogue signals from sodium and potassium ISEs recorded during normal operation in clinical analysers compared with the signals from ISFETs, shows that the ISEs are not at equilibrium during the measurement period, but that ISFETs reach a quasi-equilibrium during the same period. The reproducibility of duplicate measurements by ISFETs is similar to that achieved by commercially available clinical ISE analysers. The extent of constant and proportional bias between the ISFETs and clinical ISE analysers is similar to that between different ISE analysers. ISFET and other Si fabrication technologies enable one to manufacture arrays of either similar or dissimilar sensors on the same chip