Field-effect transistor based biosensors

Allen B, Kichambare P, Star A (2007) Carbon nanotube field-effect-transistor-based biosensors. Adv Mater 19 1439-1451... 

Chen, K.-L, Li, B.-R., and Chen, Y.-T. (2011) Silicon nanowire field-effect transistor-based biosensors for biomedical diagnosis and cellular recording investigation. Nano Today, 6,131-154. 

Field effect transistors are miniature, solid-state, potentiometric transducers (Figure 4.22) which can be readily mass produced. This makes them ideal for use as components in inexpensive, disposable biosensors and various types are being developed. The function of these semiconductor devices is based on the fact that when an ion is absorbed at the surface of the gate insulator (oxide) a corresponding charge will add at the semiconductor... 

Researchers (Benilova et al., 2006 Arkhypova et al., 2008) are developing a biosensor-based pH-sensitive field-effect transistor technology for rapid determination of glycoalkaloids. The test takes advantage of the anticholinesterase activity of the glycoalkaloids. These tests could hold great promise, analogous to the ELISA test mentioned above. 

S.V. Dzyadevych, A.P. Soldatkin, Y.I. Korpan, V.N. Arkhypova, A.V. El skaya, J.-M. Chovelon, C. Martelet and N. Jaffrezic-Renault, Biosensors based on enzyme field-effect transistors for determination of some substrates and inhibitors, Anal. Bioanal. Chem., 377 (2003) 496-506. 

Carbon nanotubes, especially SWNTs, with their fascinating electrical properties, dimensional proximity to biomacromolecules (e.g., DNA of 1 nm in size), and high sensitivity to surrounding environments, are ideal components in biosensors not only as electrodes for signal transmission but also as detectors for sensing biomolecules and biospecies. In terms of configuration and detection mechanism, biosensors based on carbon nanotubes may be divided into two categories electrochemical sensors and field effect transistor (FET) sensors. Since a number of recent reviews on the former have been published,6,62,63 our focus here is mostly on FET sensors. 

In this chapter, we have proposed to use the acid-base properties of proteins as the transducing parameter in a biosensor. The acid-base behavior of proteins can reveal some important properties with respect to both their composition (selectivity) and their concentration (sensitivity). A change in this intrinsic parameter of the protein, when used as binding ligand, must be adequately determined. The classical method of acid-base determination is by volumetric titration. Successful application in a sensor requires another approach. Since the ion-sensitive field-effect transistor (ISFET) is suitable for fast (and local) pH detection, an 1SFET can be used for protein titration. 

The first biosensor based on semiconductor technology was reported by Caras and Janata in 1980 (1). They developed a microbiosensor sensitive to penidllin based on a hydrogen ion-sensitive field effect transistor (FET) transducer in conjunction with a penicillinase-immobilized membrane. This type of biosensor offers discriminating advantages over the conventional counterpart with an electrode transducer (see Chapter 3) ... 

Widespread interest has arisen in the potential of LB films as biosensors because many believe that the incorporation of biological molecules such as enzymes will lead to novel devices. Some are exploring the deposition of biologically active molecules onto the gate electrodes or oxides of field-effect transistors, but optical sensors, probably based on fiber optics, are the most favored technique. In all cases, the aim is to couple the specificity of inter-... 

Micro pH Sensors and Biosensors Based on Electrochemical Field Effect Transistors... 

Micro pH Sensors and Biosensors Based on Electrochemical Field Effect Transistors 139 Table 10.1 Coverage for each monolayer and molecular length of each moeity... 

The direct fixation of the biocatalyst to the sensitive surface of the transducer permits the omission of the inactive semipermeable membranes. However, the advantages of the membrane technology are also lost, such as the specificity of permselective layers and the possibility of affecting the dynamic range by variation of the diffusion resistance. Furthermore, the membrane technology has proved to be useful for reloading reusable sensors with enzyme. In contrast, direct enzyme fixation is mainly suited to disposable sensors. This is especially valid for carbon-based electrodes, metal thin layer electrodes printed on ceramic supports, and mass-produced optoelectronic sensors. Field effect transistors may also be envisaged as basic elements of disposable biosensors. 

A particular type of biosensor is based upon the principle of the field effect transistor (FET) in which the semi-conducting layer is in contact with a membrane incorporating an enzyme adapted to transform a particular analyte (Figure 20.11). The chemical reaction in contact with the enzyme will modify the polarity of the insulating layer. This in turn will modify the conduction between the source and the collector (drain) of this transistor. The current between these two electrodes serves as the signal. 

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