Screening methods screen-printed electrodes

S. Andreescu, L. Barthelmebs, and J.L. Marty, Immobilization of acetylcholinesterase on screen-printed electrodes comparative study between three immobilization methods and applications to the detection of organophosphorus insecticides. Anal. Chim. Acta 464, 171—180 (2002). 

The enzyme immobilisation was carried out on 7,7,8,8-tetra-cyanoquinodimethane (TCNQ)-modified screen-printed electrodes. TCNQ allows the electrochemical oxidation of thiocholine, the product of the reaction between acetylthiocholine and the enzyme, at +100 mV (vs. Ag/AgCl) (Fig. 16.6). The enzymatic activity of the acetylcholinesterase can thus be monitored by electrochemical methods. 

Electrochemical sensors and biosensors offer the achievable opportunity of simplifying the analyses of complex matrices, outside of the laboratory, by suitable modification of appropriate electrode materials [1-5]. One of the most attractive methods for the fabrication of such devices involves the use of screen-printing technology. This allows the (bio)sensors to be manufactured in a wide range of geometries at low cost, particularly when carbon is used therefore, this allows the devices to become disposable [1,2]. A typical screen-printed electrode design commonly used in our laboratories for prototype investigations is shown in Fig. 23.1. 

Stability of Prussian blue modified screen-printed electrodes The operational stability of all the PB-modified sensors is a critical point, especially at neutral and alkaline pH. A possible explanation for reduced stability could be the presence of hydroxyl ions at the electrode surface as a product of the H202 reduction. Hydroxyl ions are known to be able to break the Fe-CN-Fe bond, hence solubilising the PB [21]. An increased stability of PB at alkaline pH was first observed by our group after adopting a chemical deposition method for the modification of graphite particles with PB for the assembling of carbon paste electrodes [48]. 

An extraction procedure performed by sonication method for dried marine sediments and soil followed by the analysis of the extracts using an electrochemical immunosensor based on magnetic beads and carbon screen-printed electrodes is described in the protocol (see Procedure 25 in CD accompanying this book). 

Immobilise the glucose oxidase onto the platinum electrode surface with the cross-linking method as described previously for the immobilisation of enzymes on screen-printed electrodes [2],... 

Thus, this review will focus on an electrochemical genosensor developed using carbon screen-printed electrodes as the transducers the methods to immobilize DNA probes... 

Applications. A biotinylated GOX-based biosensor was developed based on a new electropolymerized material consisting of a pol3rp3uidyl complex of ruthenium(II) functionalized with a pyrrole group [90]. Because histidine, lysine and arginine functions also coordinate Os /Os , biosensors based on co-electrodeposited GOX, HRP, soybean peroxidase (SBP) and laccase with redox Os /Os polymer have been developed [89]. A metal chelate formed by nickel and nitrilotriacetic acid was used to modify a screen-printed electrode surface. The functionalized support allowed stable attachment of acetylcholinesterase and the resulting biosensor was used for sensitive detection of organophosphorus insecticides [91]. This method is attractive because it ensures a controlled and oriented enzyme immobilization, considerably improving the sensitivity and the detection limit. 

The aim of this work is to demonstrate how the screen printed electrodes (SPEs) can be used for on site heavy metals monitoring in surface waters in the frame of the WFD. The sensors used consist of mercury-coated screen-printed electrodes coupled with square wave anodic stripping voltammetry (SWASV) (Palchetti et al., 1999). Three metals Cu, Cd, and Pb which are classically analysed in water matrices have been considered. Moreover, Cd and Pb belong to the priority substances list of the WFD. Performance criteria of the device are first established to evaluate the level of confidence of the method. The potential use of the device and its main advantages are then highlighted through two illustrative field applications. 

Abstract. The biosensors described in this work, for the monitoring of pesticides, are based on acetylcholinesterase immobilized on the surface of screen-printed electrodes. The principle of the biosensor is that the degree of inhibition of an enzyme sensor by a pesticide is dependent on the concentration of that pesticide. The DPV technique was used as a detection method and methyl-paraoxon as a reference pesticide for sensor calibration. 

Most biosensors based on AChE have the enzymes immobilized on the surface of the sensor. The inhibition reaction being irreversible, the membrane with immobilized enzyme has to be replaced after several measurements or the biosensor can be use for only one determination. Due to this fact, the researchers tried to realize pesticide biosensors with a renewable surface or disposable biosensors based on screen-printed electrodes (SPE). The screen-printing technology provides a simple, fast and inexpensive method for mass production of disposable biosensors for different biomolecules starting with glucose, lactate and finishing with environmental contaminants as pesticides (Kulys et al., 1991) and herbicides (Skladal, 1992). 

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