ENFET

A. Poghossian, T. Yoshinobu, A. Simonis, H. Ecken, H. Liith and M.J. Schoning, Penicillin detection by means of field-effect based sensors EnFET, capacitive EIS sensor or LAPS Sens. Actuators B 78, 237-242 (2001). 

Enzyme-immobilized FETs (ENFETs), 22 269. See also Enzyme ion-selective field-effect transistor (ENFET) Field effect transistors (FETs)... 

ENZYME ION-SELECTIVE FIELD-EFFECT TRANSISTOR (ENFET)... 

The enzyme-containing FET, called ENFET, is fabricated from an ISFET by casting a thin membrane containing the enzyme over an ion-selective membrane... 

Due to the fact that nearly all ENFET approaches lead to insufficient or unsatisfactory sensor performance, no ISFET based biosensor has been fully commercialized for wider applications to date. 

A new development in the field of potentiometric enzyme sensors came in the 1980s from the work of Caras and Janata (72). They describe a penicillin-responsive device which consists of a pH-sensitive, ion-selective field effect transistor (ISFET) and an enzyme-immobilized ISFET (ENFET). Determining urea with ISFETs covered with immobilized urease is also possible (73). Current research is focused on the construction and characterization of ENFETs (27,73). Although ISFETs have several interesting features, the need to compensate for variations in the pH and buffering capacity of the sample is a serious hurdle for the rapid development of ENFETs. For detailed information on the principles and applications of ENFETs, the reader is referred to several recent reviews (27, 74) and Chapter 8. 

ENFET Enzyme-immobilized field effect transistor... 

This, in addition to the less common detection techniques for these oxygenases (e.g., ENFET [180] or calorimetric [181]), the search for new laccases, the degree of maturity that these sensors have generally achieved and, mainly, the search for better or fit-for-purpose performance requires a focus on the following features ... 

Under these conditions a dynamic range between 1 pph and 1.3 ppm can be obtained [322]. Hammerle et al. have described an electrochemical ceU containing the enzyme electrode that can directly operate in the gas phase with a limit of detection of 0.3 ppm and no loss of response during 7 h of operation [323]. Formaldehyde dehydrogenase has also been incorporated into a field-effect transistor for the measurement of catalytically-produced protons and the ENFET incorporated to a sampling system that strips the aldehyde into an aqueous phase [324]. 

Figure 11. Schematic of ENFET assembled with Pt-DENs/GOx using LbL technique (Adapted from Ref. [133]).

GOx Enzyme-linked field effecl transistor (ENFET) PAMAM(G4)-Pt LbL Potentiometry vs SCE 10 mM Phosphate buffer and 100 mM NaCl at pH 7.4 Linear range - 0.25-2.0 mM Detection limit 0.15 mM Response time = 200s Repetability for 5 measurements storage stability measured for 30 days 12.5 mM/mV [133]... 

Fig. 16 Enzyme field-effect transistor (ENFET) based on LbL assembly of enzymes with Mn02 nanoparticle and polyelectrolyte on the surface of ion-sensitive field-effect transistor (ISFET)...

---