Immuno-FET

Field-effect Transistors Enzyme FETs and immuno FETs (IMFETs) are based on principles similar to those valid in potentiometric membrane biosensors. The enzyme is immobihzed on top of the ion-selective membrane on the gate of the FET. For construction of ENFETs, usually double-gate FETs are used employing one gate as a reference system, covered only with a layer of the immobilization matrix, and allowing for the real-time compensation of pH modulations, temperature, and drift. Mostly, pH-sensitive FETs (ISFET)... 

By substituting and Uqs = Ur into Eqs. (9) and (10), the dependencies of the drain current, on the activity of the ions are obtained. An analogous expression holds for CHEMFETs with another ion-selective membrane, ENFETs (enzyme-layer FETs), IMFETs (immuno-FETs), BIOFETs (with attached bioreactor containing bacteria, whole cells, tissue slices etc.) and REFETs (ISFETs with a constant activity of ions used as a reference to indicating ISFETs). 

An antibody is an electrically charged protein, and its coupling with an antigen can give rise to variation in the dielectric constant which is measurable with a semiconductor sensor (see 4.6.1). Thus, immuno-FET (or IMFET, immuno-field-effect transistors) are constructed by immobilizing immunoagents on field-effect transistors (FET). 

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