Enzyme biosensors pesticides detection

Biosensors ai e widely used to the detection of hazardous contaminants in foodstuffs, soil and fresh waters. Due to high sensitivity, simple design, low cost and real-time measurement mode biosensors ai e considered as an alternative to conventional analytical techniques, e.g. GC or HPLC. Although the sensitivity and selectivity of contaminant detection is mainly determined by a biological component, i.e. enzyme or antibodies, the biosensor performance can be efficiently controlled by the optimization of its assembly and working conditions. In this report, the prospects to the improvement of pesticide detection with cholinesterase sensors based on modified screen-printed electrodes are summarized. The following opportunities for the controlled improvement of analytical characteristics of anticholinesterase pesticides ai e discussed ... 

Absorbance- and reflectance-based measurements are widespread, as there are many enzymatic reaction products or intermediates that are colored or if not, can react with the appropriate indicator. Sensors using acetylcholinesterase for carbamate pesticides detection are an example of indirect optical fiber biosensors. This enzyme catalyses the hydrolysis of acetylcholine with concomitant decrease in pH41 ... 

In the following section an example of the use of disposable graphite sensor based for food analysis will be described. In particular, the use of these sensors to develop enzymatic biosensors for pesticide detection based on AChE (acetylcholinesterase) enzyme inhibition will be described. 

Meng, X., Wei, J., Ren, X., et al., 2013. Simple and sensitive fluorescence biosensor for detection of organophosphorus pesticides using H202-sensitive quantum dots/bi-enzyme. Biosens. Bioelectron. 47, 402-407. 

On a different setup, Du et al. [31] cast sol-gel silica/gold nanoparticle nanocomposite films on a glassy carbon electrode, which was then impregnated with an acetylcholinesterase (AChE) enzyme (Figure 46.10). The construct was used as a biosensor for organophosphorus pesticide detection. In this system, gold nanoparticles not only offered a biocompatible microenvironment to retain the activity of adsorbed enzyme molecules but also acted as a wire to enhance the direct electron transfer rate between the enzyme active centers and the electrode surface, which otherwise would be blocked by the thick protein shell of the enzyme chemical structure. 

AChE has been used extensively for the enzymatic detection of organophos-phates as well as carbamate pesticides, nerve agents, several natural toxins,and some drugs. Hence, AChE is widely used as a potent recognition element for the construction of biosensors for pesticide detection. Biosensors based on AChE as well as butyrylcholinesterase were first reported during the 1980s. Since then, there has been a continuous improvement of cholinesterase-based biosensors due to the gradual improvement of transducer devices and the availability of pure enzymes. ... 

The design and implementation of a portable fiber-optic cholinesterase biosensor for the detection and determination of pesticides carbaryl and dichlorvos was presented by Andreou81. The sensing bioactive material was a three-layer sandwich. The enzyme cholinesterase was immobilized on the outer layer, consisting of hydrophilic modified polyvinylidenefluoride membrane. The membrane was in contact with an intermediate sol-gel layer that incorporated bromocresol purple, deposited on an inner disk. The sensor operated in a static mode at room temperature and the rate of the inhibited reaction served as an analytical signal. This method was successfully applied to the direct analysis of natural water samples (detection and determination of these pesticides), without sample pretreatment, and since the biosensor setup is fully portable (in a small case), it is suitable for in-field use. 

Cell components or metabolites capable of recognizing individual and specific molecules can be used as the sensory elements in molecular sensors [11]. The sensors may be enzymes, sequences of nucleic acids (RNA or DNA), antibodies, polysaccharides, or other reporter molecules. Antibodies, specific for a microorganism used in the biotreatment, can be coupled to fluorochromes to increase sensitivity of detection. Such antibodies are useful in monitoring the fate of bacteria released into the environment for the treatment of a polluted site. Fluorescent or enzyme-linked immunoassays have been derived and can be used for a variety of contaminants, including pesticides and chlorinated polycyclic hydrocarbons. Enzymes specific for pollutants and attached to matrices detecting interactions between enzyme and pollutant are used in online biosensors of water and gas biotreatment [20,21]. 

JL Martin, N Mionetto, T Noguer, F Ortega, C Roux. Enzyme sensors for the detection of pesticides. Biosensors Bioelectronics 8 273-280, 1993. 

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