Transducers amperometric

Figure 27.10 (A) Dual parallel and (B) dual series thin-layer amperometric transducers.

Figure 27.11 Parallel opposed thin-layer amperometric transducer.

Carralero, V., A. Gonzalez-Cortes, P. Yanez-Sedeno, et al. 2007. Nano structured progesterone immu-nosensor using a tyrosinase-colloidal gold-graphite-Teflon biosensor as amperometric transducer. Anal. Chim. Acta 596 86-91. 

The challenge of establishing hundreds or thousands of electrical contacts if such amperometrically transduced microphysiometers are massive parallelized can be satisfied by multiplexing the individual sensors by CMOS components integrated on a silicon wafer [113]. 

In our earlier work we have studied the realization of an amperometric transducer using thin film and photolithography techniques (7) as well as that of an AI2O3 type pH-ISFET (2). The use of the former in an enzymatic glucose electrode (3) and of the latter in for example a K+ sensitive device (4) has been reported. In both cases the control of membrane thicknesses and adhesion was the most critical parameter of the sensor realization. In this paper we will focus on different on-wafer and on-chip... 

Amperometric transducers measure the current (flux of electrons) caused by oxidation or reduction of the species of interest when a voltage is applied between the working and the reference electrode. Often, oxygen serves as electron acceptor but interferences have encouraged development of new methods to avoid this, e.g. controlled oxygen supply and the application of mediators, such as ferrocene, e.g. [169]. Other determinations focus on the... 

Potentiometric transducers measure the potential between the sensing element and a reference element. Thus, in contrast to amperometric transducers, practically no mass transport occurs the response depends on the development of the thermodynamic equilibrium. pH changes often correlate with the measured substance because many enzymatic reactions consume or produce protons. 

Electrochemical antibody-based sensors 8.3.3.2 Amperometric transducers... 

For amperometric transducers, it is the regeneration of Eo by reaction with an oxidant (O2 or another mediating species M2+) that results in the species actually measured by the transducer. This reaction, Eq. 7.8, results in a flux for the regeneration of Er given by Eq. 7.9 ... 

Yang, Q.L, Atanasov, P., and Wilkins, E. (1997) A novel amperometric transducer design for needle-type implantable biosensor applications. Electroanalysis, 9 (15), 1252-1255. 

Fig. 2. The progesterone immunosensor using a colloidal gold—graphite—Teflon—tyrosinase composite biosensor as amperometric transducer.

The principle for biosensors and immunosensors is based on the biochemical reaction produced at the surface of the electrode followed by the detection of one of the products formed in the biochemical reaction by using a certain transducer. In this case, the selectivity of the biochemical reaction must be correlated with the sensitivity of the transducer.264 The best correlation is accomplished when amperometric transducers are utilized. The potentiometric transducers in most cases are not suitable for biosensor design. For the design of immunosensors, the potentiometric transducer is not always able to measure the product obtained in the immunological reaction because it is known that the reaction between the antigen and the antibody is very sensitive. In certain cases the selectivity of transducer vs. different products of the biochemical reaction must also be considered. Because of the high sensitivity of the piezoelectric transducers, their selectivity is limited, and they cannot assure the best results when used in biosensor or immunosensor design. 

With amperometric transducers, two types of pesticides biosensors can be constructed. One possibility is a two-enzyme system using AChE and choline oxidase (ChOD) and thus employing either an oxygen sensor (Campanella et al., 1991) or a hydrogen peroxide detector (Marty et al., 1992 Palleschi et al., 1992) as the internal transducer. 

All chemical sensors consist of a transducer, which transforms the response into a signal that can be detected (a current in the case of amperometric sensors) and a chemically selective layer. The transducer may be optical (e.g., a fiberoptic cable sensor), electrical (potentiometric, amperometric), thermal, and so on. We are concerned here with amperometric transducers. 

Erlenkotter A, Kottbus M, Ghemnitius GG. Flexible amperometric transducers for biosensors based on a screen printed three electrode system. J Electroanal Ghem 2000 481 82-94. 

Such a simultaneous incorporation of CNT and glucose oxidase imparted bio-catalytic and electrocatalytic properties onto amperometric transducers and represented a facile and effective route for preparing an enzyme electrode. 

Potentiometric, capacitive, and amperometric transducers have been used for direct and indirect electrochemical immunoassays. However, due to their fast detection, broad linear range, and low detection limit, amperometric transducers are preferred. 

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