Enzyme inhibition-based biosensors

Survey of enzyme inhibition based biosensors for heavy metals for the last 5 years... 

M.D. Luque de Castro and M.C. Herrera, Enzyme inhibition-based biosensors and biosensing systems questionable analytical devices, Biosens. Bioelectron., 18 (2003) 279-294. 

A. Amine, H. Mohammadi, I. Bourais and G. Palleschi, Enzyme inhibition based biosensors for food safety and environmental monitoring (review), Biosens. Bioelectron., 21 (2005) 1405-1423. 

M. Campas, D. Szydlowska, M. Trojanowicz and J.-L. Marty, Enzyme inhibition-based biosensor for the electrochemical detection of microcystins in natural blooms of cyanobacteria (2006), submitted for publication. 

Sheo, L., Upadhyay, B., Verma, N., 2013. Enzyme inhibition based biosensors a review. Anal. Lett. 46, 225-241. 

Amine A, Mohanunadi H, Bourais I, Palleschi G (2006) Enzyme inhibition-based biosensors f(OT food safely and envirraunental monitoring. Biosens Bioelectron 21 1405-1423... 

A huge number of methods based on enzyme inhibition-based biosensors can be found in the literature. Most times (57.6 %) acetylcholinesterase, butyrylchoU-nesterase, or cholinesterase are used followed by t3Tosinase (13 %) mainly combined with electrochemical procedures (44.5 % amperometric, 35.8 % potentiometric, frequently based on oxygen and pH measurements, and, to a very less extent, piezoelectrical). 

One of the most regrettable characteristics of enzyme inhibition-based biosensors is the different inhibition degree caused by different inhibitors. An example of this behavior is an amperometric acid phosphatase inhibition-based biosensor proposed by Mazzei et al., which shows different inhibition efficiency towards organophosphorus and carbamate compounds (the latter with a weaker inhibition efficacy and higher detection limits, as a result). 

Mainly, two principles are used in electrochemical pesticide biosensor design, either enzyme inhibition or hydrolysis of pesticide. Among these two approaches inhibition-based biosensors have been widely employed in analysis due to the simplicity and wide availability of the enzymes. The direct enzymatic hydrolysis of pesticide is also extremely attractive for biosensing, because the catalytic reaction is superior and faster than the inhibition [27],... 

Although the inhibition-based biosensors are sensitive, they are poor in selectivity and are rather slow and tedious since the analysis involves multiple steps of reaction such as measuring initial enzyme activity, incubation with inhibitor, measurement of residual activity, and regeneration and washing. Biosensors based on direct pesticide hydrolysis are more straightforward. The OPH hydrolyzes ester in a number of organophospho-rus pesticides (OPPs) and insecticides (e.g. paraoxon, parathion, coumaphos, diazinon) and chemical warfare agents (e.g. sarin) [53], For example, OP parathion hydrolyzes by the OPH to form p-nitrophenol, which can be measured by anodic oxidation. Rainina... 

Bertocchi R, Ciranni E., Compagnone D., Mageauru V., Palleschi G., Pirvutoiu S., and Valvo L., Elow injection analysis of mercury (II) in pharmaceuticals based on enzyme inhibition and biosensor detection, J. Pharm. Biom. Anal., 20, 263-269, 1999. 

T. M. Park, E. I. Iwuoha, M. R. Smyth, Development of a Sol-gel Enzyme Inhibition-based Amperometric Biosensor for Cyanide. Electroanalysis, 9 (1997) 1120-1123. 

Biosensors may provide the basis for in-field analyses and real-time process analysis. However, biosensors are generally limited to the determination of a limited range of analytes in defined matrices. Enzyme-based biosensors, principally acetylcholinesterase (AChE) inhibition, have been successfully used in environmental analysis for residues of dichlorvos and paraoxon, " carbaryl " and carbofuran. " Immunochemically based biosensors may be the basis for the determination of pesticide residues in liquid samples, principally water and environmental samples, but also fruit juices. The sensors can be linked to transducers, for example based on a piezo-... 

In AChE-based biosensors acetylthiocholine is commonly used as a substrate. The thiocholine produced during the catalytic reaction can be monitored using spectromet-ric, amperometric [44] (Fig. 2.2) or potentiometric methods. The enzyme activity is indirectly proportional to the pesticide concentration. La Rosa et al. [45] used 4-ami-nophenyl acetate as the enzyme substrate for a cholinesterase sensor for pesticide determination. This system allowed the determination of esterase activities via oxidation of the enzymatic product 4-aminophenol rather than the typical thiocholine. Sulfonylureas are reversible inhibitors of acetolactate synthase (ALS). By taking advantage of this inhibition mechanism ALS has been entrapped in photo cured polymer of polyvinyl alcohol bearing styrylpyridinium groups (PVA-SbQ) to prepare an amperometric biosensor for... 

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). 

W.E. Lee, H.G. Thompson, J.G. Hall and D.E. Bader, Rapid detection and identification of biological and chemical agents by immunoassay, gene probe assay and enzyme inhibition using a silicon-based biosensor, Biosens. Bioelectron., 14(10-11) (2000) 795-804. 

Electrochemical biosensors for heavy metals based on enzyme inhibition... 

ANALYTICAL CHARACTERIZATION OF BIOSENSORS-BASED ENZYME INHIBITION... 

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. 

P.W. Alexander and G.A. Rechnitz, Enzyme inhibition assays with an amperometric glucose biosensor based on thiolate self-assembled mono-layer, Electroanalysis, 12 (2000) 343-350. 

Z. Guang-Ming, T. Lin, S. Guo-Li, H. Guo-He and N. Cheng-Gang, Determination of trace chromium (VI) by an inhibition-based enzyme biosensor incorporating an electro polymerized aniline membrane and... 

H. Mohammadi, A. Amine, S. Cosnier and C. Mousty, Mercury-enzyme inhibition assays with an amperometric sucrose biosensor based on a trienzymatic-clay matrix, Anal. Chim. Acta, 543 (2005) 143-149. 

The main drawback of acetylcholinesterase-based biosensors is the lack of selectivity because, as we mentioned, this enzyme is inhibited not only by anatoxin-a(s) but also by insecticides such as organ-ophosphorates and carbamates. This problem can be overcome by the choice of specific mutant enzymes. The combined use of mutants highly sensitive to anatoxin-a(s) and resistant to most insecticides and vice versa allows us to unambiguously discriminate between the cyanobacterial toxin and insecticides. 

OPH-based biosensors have been fully discussed in previous reviews [2,165]. AChE-based biosensors are based on the principle that OP pesticides have an inhibitory effect on the activity of AChE that may be permanent or partially reversible. The extent of the inhibition is directly related to the concentration of the pesticide and therefore enzyme activity may be used as a measure of the inhibition [166]. The amperometric measurement of AChE activity can be based on the measurement of any of the following three mechanisms [167] (1) production of hydrogen peroxide from choline, (2) oxygen consumption during the enzyme reaction or (3) production of electroactive compounds directly from the oxidation of acetylthiocholine chloride such as thiocholine. The measurement of hydrogen peroxide and oxygen consumption has been described in more details in other reviews [167]. 

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