Biosensors based on enzymes

T. Noguer, B. Leca, G. Jeanty, and J.L. Marty, Biosensors based on enzyme inhibition detection of organophosphorus and carbamate insecticides and dithiocarbamate fungicides. Field Anal. Chem. Tech. 3, 171-178 (1999). 

For these reasons, microbial sensors are less suitable for the determination of individual analytes. However, some practical apphcations for biosensors based on enzymes or antibodies for the specific determination of environmentally relevant compounds can be expected soon [11]. Furthermore, in some cases defined specific metabolic pathways in microorganisms are used, leading to microbial sensors for more selective analysis for those environmental pollutants which cannot be measured by the use of simple enzyme reactions, e.g., aromatic compounds and heavy metals. In this context it is also important to mention the aspect of bio availability, a parameter which is included by the measuring procedure of microbial sensors as an integral effect. 

Biosensors based on enzyme inhibition are still limited in analytical applications since these sensor technologies are not usually able to discriminate various toxic compounds in the same sample. 

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. 

C. Malitesta and M.R. Guascito, Heavy metal determination by biosensors based on enzyme immobilised by electropolymerisation, Biosens. Bioelectron., 20 (2005) 1643-1647. 

Trojanowicz, M. and Krawczyk, T.K.V. (1995) Electrochemical biosensors based on enzymes immobilized in electropolymerized films. Microchimica Acta, 121 (1-4), 167-181. 

In the development and application of biosensors based on enzymes several factors required for the catalytic process have to be taken into account, which are either directly involved in catalysis or influence the formation of the enzyme-substrate complex. They are designated coenzymes, prosthetic groups, and effectors. 

Limitations for biosensors based on enzyme inhibition is that the assay may need multistep incubation, and the assay formats require the use of substrates/cofactors and mediators depending on the enzyme applied in the sensor format. The irreversible... 

Immobilized enzymes have been used for the formation of biosensors that are selective for numerous enzyme substrates (42). We have evaluated the potential of gamma irradiation as a means of immobilizing an enzyme in a polymer matrix on an electrode surface. The previously mentioned advantageous features of the gamma radiation method are potentially useful in the formation of biosensors based on enzymes immobilized in polymer films. 

Figure 4.10 Scheme diagram of the biosensor based on enzyme-catalyzed... 

Reports on the use of monomeric MPc complexes for the electrocatalysis of phenols are rare, hence the use of some polymeric MPc complexes will be included in this section. Biosensors based on enzymes have been developed for many electrochemical analyses. The use of MPc complexes as part of the enzyme improves the sensitivities of the biosensors. Ozsoz et al. used CoPc monomer dispersed in mushroom tissue electrode as a catalyst for the analysis of phenolic compounds The enzymatic reaction between mushroom and the phenolic compounds was coupled with the catalytic activity of CoPc. The CoPc dispersed electrodes gave shorter response times and lower potentials compared to conventional tissue biosensors . 

An extended lifetime of at least several months . This can be a major problem, particularly with biosensors based on enzyme or antibodies due to... 

A number of other features follow from the relatively large size of the diffusion zone when compared to the electrode radius. One of these is quite significant to biosensors based on enzyme systems. The large diffusion zone radidly dilutes the products of the electrode reaction, thus catalytic mechanisms of the type shown in Table 8.2, mechanisms 3-5, are not perceived at microelectrodes, unless the rate constant for the reaction is fast. It can be shown that for a reversible electrode reaction, the ratio of the catalytic current (i kc) to the faradaic current obtained in the absence of the homogeneous reaction is given by... 

Cosnier, S., Senillou, A., Gratzel, M., et al. (1999) A glucose biosensor based on enzyme entrapment within polypyrrole films electrodeposited on mesoporous titanium dioxide. J. 

M Elmgren, Amperometnc Biosensors Based on Enzymes Wired by Redox Polymers Acta Univ Ups, Comprehensive Summaries of Uppsala Dissertions from the Faculty of Science 471 55pp Uppsala ISBN 91-554-3175-5... 

Ramanathan M, Simonian AL (2007) Array biosensor based on enzyme kinetics monitoring by fluorescence spectroscopy application for neurotoxins detection. Biosens Bioelectron 22 3001-3007... 

Numerous biosensors based on enzymes have been developed due to the success of the enzymatic biosensor for glucose. Research on enzyme-based biosensors... 

Biosensors based on enzymes have high sensitivity and selectivity. A variety of microbial biosensors have also been developed. However, it still remains a great challenge to develop a rapid, inexpensive but sensitive method for real samples. Compared to enzymatic biosensors, development of a highly satisfactory microbial biosensor is still hampered because they suffer from long response time, low sensitivity, and poor selectivity. The trends for the development of biosensors lie in miniaturization of the devices, nanotechnology, and biotechnology. Disposable screen-printed sensors have been developed for industrial wastes or natural water. Metal nanoparticles can enhance the electron transfer between redox center in proteins and electrode surface and show promise for detection... 

Shimomura T, Itoh T, Sumiya T, Mizukami F, Ono M (2009) Amperranetric biosensor based on enzymes immobilized in hybrid mesoptuous membranes for the determinatimi of acetylcholine. Enzyme Microb Tech 45(6—7) 443—448. doi 10.1016/j.enzmictec.2009.08.007... 

Although being sensitive and useful sensors for environmental monitoring, biosensors based on enzyme inhibition have some limitations. They have a Iraig and tedious protocol that requires long incubation with inhibitors prior to analysis for good sensitivity and require reactivation of the enzyme which is inhibited irreversibly by OPs. Since AChE is inhibited by neurotoxins, which include not only OP pesticides but also carbamate pesticides and many other compounds, these analytical tools are not selective and carmot be used for quantification of either an individual or a class of pesticides that may be required for monitoring detoxification processes. 

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