Biosensors with amperometric detection

Enzyme-Based Biosensors with Amperometric Detection... 

Adanyi, N., Szabo, E. E., and Varadi, M. 1999. Multi-enzyme biosensor with amperometric detection for determination of lactose in milk and dairy products. Fur. Food Res. Technol. 209 206—226. 

Recently, by embedding glucose oxidases inside Ti02 nanotube channels and electropolymerizing pyrrole for interfacial immobilization we have constructed a biosensor for amperometric detection and quantitative determination of glucose in a phosphate buffer solution (pH 6.8) under a potentiostatic condition (-0.4V versus SCE) [90], Promising results are obtained with a response time below 5.6 s and a detection limit of 2.0xl0"3 mM. 

A biosensor for sarcosine can be constructed based on sarcosine oxidase entrapped in nafion, with amperometric detection using manganese dioxide-modified screen-printed electrodes. The LOD is 28pmoll. ... 

The potential for the coexistence of several enzymes in tissue materials can also be a major drawback as it can affect the selectivity of the device when used in complex sample media. Some of the strategies that have been employed for improving the selectivity of tissue-based biosensors include the use of activators to promote the primary reaction, inhibitors to suppress the undesirable reactions, or preincubation of the desired substrate. Under favorable conditions, the multienzyme activity of the tissue can be exploited for the detection of multicomponents in real samples. For example, with amperometric detection, such multicomponent detection may require the application of different potentials to achieve improved selectivity. 

Putrescine oxidase and xanthine oxidase have also been used to develop an FIA biosensor system (two lines) combining the two enzymes immobilized on their respective electrodes for quality control of vacuum-packed beef by simultaneous measurement of putrescine and cadaverine and hypoxanthine and xanthine (Yano et al., 1995). Okuma et al. (2000) developed an enzyme reactor system with amperometric detection for the determination of putrescine, cadaverine, and spermidine in chicken. The system had a reactor in which putrescine oxidase was immobilized on chitosan porous beads, and an... 

MWNTs favored the detection of insecticide from 1.5 to 80 nM with a detection limit of InM at an inhibition of 10% (Fig. 2.7). Bucur et al. [58] employed two kinds of AChE, wild type Drosophila melanogaster and a mutant E69W, for the pesticide detection using flow injection analysis. Mutant AChE showed lower detection limit (1 X 10-7 M) than the wild type (1 X 10 6 M) for omethoate. An amperometric FIA biosensor was reported by immobilizing OPH on aminopropyl control pore glass beads [27], The amperometric response of the biosensor was linear up to 120 and 140 pM for paraoxon and methyl-parathion, respectively, with a detection limit of 20 nM (for both the pesticides). Neufeld et al. [59] reported a sensitive, rapid, small, and inexpensive amperometric microflow injection electrochemical biosensor for the identification and quantification of dimethyl 2,2 -dichlorovinyl phosphate (DDVP) on the spot. The electrochemical cell was made up of a screen-printed electrode covered with an enzymatic membrane and combined with a flow cell and computer-controlled potentiostat. Potassium hexacyanoferrate (III) was used as mediator to generate very sharp, rapid, and reproducible electric signals. Other reports on pesticide biosensors could be found in review [17],... 

Fortier [6] found that AQ polymer from Eastman was not deleterious for the activity of a variety of enzymes such as L-amino acid oxidase, choline oxidase, galactose oxidase, and GOD. Following mixing of the enzyme with the AQ polymer, the mixture was cast and dried onto the surface of a platinum electrode. The film was then coated with a thin layer of Nafion to avoid dissolution of the AQ polymer film in the aqueous solution when the electrode was used as a biosensor. These easy-to-make amperometric biosensors, which were based on the amperometric detection of H202, showed high catalytic activity. 

Figure 19.7—Amperometric detection of glucose. The reaction cycle is shown on the left. A sandwich-type biosensor involving glucose oxidase co-immobilised with an osmium-based redox mediator in a polyvinyl polymer is shown on the right.

S. Pati, M. Quinto, F. Palmisano and P.G. Zambonin, Determination of choline in milk, milk powder, and soy lecithin hydrolysates by flow injection analysis and amperometric detection with a choline oxidase based biosensor, J. Agric. Food Chem., 52(15) (2004) 4638-4642. 

Another class of enzymes that has found wide application in the biosensor field in the last decades is that of the cholinesterases which have been mainly used for the detection of pesticides. For the amperometric detection of cholinesterase activity, both the substrates acetylcholine and acetylthiocholine have been extensively used [6-9], the latter being preferred because this avoids the use of another enzyme, choline oxidase, which is usually coupled with acetylcholinesterase. However, the amperometric measurement of thiocholine, produced by... 

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