ISFET affinity sensor

The so-called ion-step method represents a newly developed measurement concept for potentiometric detection and quantification of adsorbed biomolecules in which modified ion-sensitive field-effect transistors (ISFETs) are used. The ion-step method is based on a dynamic measuring principle, whereas many other potentiometric methods are static and measure in a state of thermo-dynamic equilibrium. A number of authors report on measuring protein adsorption by equilibrium potentiometry, but in all measurements the observed responses were poor (1 , 2 ). The new measuring method is therefore an important alternative method for detection of adsorbed protein. In Subheading 1.2. , a short explanation will be given for the disappointing results obtained with detection of protein by equilibrium potentiometry. Thereafter, the ion-step method will be described briefly and at the end of this introduction, the use of an ISFET affinity sensor for the measurement of heparin will be described.