Redox enzyme linked electrochemical sensors: Theory meets practice

Hall, Elizabeth A. H.; Gooding, J. Justin; Hall, Carl E.

doi:10.1007/bf01248246

Cited by 60 publications

(55 citation statements)

References 103 publications

(73 reference statements)

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“…The insensitivity in dynamic range to the enzyme loading is in contrast to thick film enzyme electrodes where an increase in catalytic activity is shown to provide an increase in sensitivity but at the cost of a reduced dynamic range. 35,57 Increasing mediator concentration has an even more dramatic and positive effect on the response of the SAM enzyme electrodes (Fig. 6).…”

Section: Tuning the Response Of The Enzyme Electrodementioning

confidence: 99%

“…This ready supply of mediator is in direct contrast to thick-film enzyme electrodes which are usually cosubstrate limited. 35,37,38 Hence, with monolayer enzyme electrodes, the ready supply of mediator provides for efficient enzyme turnover, a high sensitivity per enzyme molecule and a broad dynamic range. The disadvantage however, is that the enzyme electrode is kinetically rather than mass-transport limited.…”

Section: A Reference Enzyme Electrodementioning

confidence: 99%

“…17 electrodes where the enzyme electrode rarely responds to glucose concentrations above 40 mM. 35 Theoretical studies of the reaction-diffusion system defined by a monolayer enzyme electrode provides an explanation for both the broad dynamic range and the outstanding sensitivity of the SAM enzyme electrode. 2,36 The modelling indicates that the close proximity of the enzyme to the electrode results in little diffusional barrier for the reduced mediator to travel to the electrode where it is oxidized, regenerating p-benzoquinone, and thus giving the current signal.…”

Section: A Reference Enzyme Electrodementioning

confidence: 99%

“…In the case of thick film enzyme electrodes this can be achieved in a number of ways such as by varying the amount of enzyme, the thickness of the enzyme layer, the partition coefficient or the amount of mediator. 35 With a SAM enzyme electrode we have investigated how to control the output of the sensor via varying the amount of enzyme immobilized and the concentration of mediator.…”

Section: Tuning the Response Of The Enzyme Electrodementioning

confidence: 99%

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Parameters Important in Fabricating Enzyme Electrodes Using Self-Assembled Monolayers of Alkanethiols

et al. 2001

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The immobilization of enzymes on the surface of electrodes modified with self-assembled monolayers (SAMs) provides a number of advantages as a method for the fabrication of enzyme electrodes. Using SAMs has the potential to provide enzyme electrodes with a high degree of reproducibility, 1,2 molecular level control over the spatial distribution of the immobilized enzymes 3-14 and the immobilization of the enzyme close to the electrode thus allowing direct electron transfer to be achieved. [15][16][17][18][19][20][21][22][23][24] These advantages have resulted in a recent surge in research into self-assembled monolayers for biosensor applications in general, and enzyme electrodes in particular. [25][26][27] However, despite the plethora of biosensor research papers using self-assembled monolayers as the base onto which the biomolecule is immobilized, there has been very little fundamental research into what steps are important in the fabrication process or which parameters control the response of the resultant biosensor.Alkanethiols modifying gold are the most popular SAMs. 25,26 The interaction between the thiol groups and the gold results in a strong pseudocovalent bond 28 which is stable throughout the potential range of 0.8 V to -1.4 V versus Ag/AgCl before being oxidatively or reductively desorbed. 29,30 If the alkanethiol has appropriate chemical functionality, such as an amine or carboxylic acid moiety, then once the SAM is formed, enzymes and other biomolecules can be easily covalently bound to the SAM. In this way, a monolayer or submonolayer of enzyme is immobilized. For enzyme electrodes a short alkyl chain alkanethiol, usually three carbons long, is chosen so that the enzyme is as close as possible to the electrode. An additional advantage of the short alkyl chain is that a relatively disordered SAM is formed which means the underlying metal is still electrochemically accessible. In contrast, if a long chain alkanethiol is used the electrode is passivated unless defects are deliberately introduced into the SAM. 31 There are a number of steps in the fabrication of an enzyme electrode using an alkanethiol. First, the metal surface must be prepared and cleaned. The alkanethiol must self-assemble onto the metal, followed by activation of the chemical functionality of the SAM, leading finally to the exposure of the activated SAM to the enzyme which is when attachment occurs. There are however many unknowns in this fabrication process. Questions that needs answers are: what effect does the roughness of the gold surface have? How long should the metal be exposed to the alkanethiol solution to allow a stable SAM to be formed? What is the optimal procedure for activating the SAM for enzyme attachment? How long should the activated SAM be exposed to enzyme? What should the concentration of the enzyme solution be during enzyme immobilization? Does the buffer used have any effect on subsequent performance? Can the amount of enzyme immobilized be controlled and do different enzyme loadings lead to different electr...

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Section: Tuning the Response Of The Enzyme Electrodementioning

confidence: 99%

Section: A Reference Enzyme Electrodementioning

confidence: 99%

Section: A Reference Enzyme Electrodementioning

confidence: 99%

Section: Tuning the Response Of The Enzyme Electrodementioning

confidence: 99%

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Parameters Important in Fabricating Enzyme Electrodes Using Self-Assembled Monolayers of Alkanethiols

et al. 2001

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“…However, regardless of the enzyme specificity, the selectivity of these devices is compromised by electroactive species in the sample that may react directly at the transducer. The most frequent strategy to overcome this problem is to completely eliminate the interfering species by adsorption in permselective membranes [2 ± 4], multiple enzyme layers [5], mediators [6] and by on-line electrolysis [7,8].…”

Section: Introductionmentioning

confidence: 99%

A Portable Fill‐and‐Flow Channel Biosensor with an Electrode to Predict the Effect of Interferences

et al. 2004

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A portable fill-and-flow channel biosensor with a ™predictor electrode∫ is described. The predictor electrode, on the opposite channel wall and upstream of the detector electrode, allows direct evaluation of the current due to interfering species at the detector electrode. A model is developed which shows that the reaction at the upstream predictor electrode has no significant effect on the concentration distribution of the interfering species at the detector electrode. This enables a straightforward correction of the current at the detector electrode and a determination of the analyte concentration. The effect of interference from ascorbic acid in the detection of glucose in samples was efficiently removed by using such a concept. The recovery of glucose from samples containing ascorbic acid was 103% (s 12%, n 3). The approach was also applied to a biosensor for the determination of glucose in red wine samples containing polyphenolic interferents.

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From Thick Films to Monolayer Recognition Layers in Amperometric Enzyme Electrodes

1998

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Theoretical models of the conventional thick‐film enzyme electrode and monolayer electrodes are used to determine the important parameters in defining the response of both types of biosensors with regard to their reproducible fabrication. The response of the thick‐film biosensors are very sensitive to the thickness of the enzyme layer and therefore highly precise methods of depositing the enzyme layer are required if reproducible biosensors are to be manufactured. Covalent attachment of an enzyme to a monolayer of alkanethiols self‐assembled onto a gold electrode could potentially provide this more precise fabrication method. A model for monolayer enzyme electrodes gives an excellent fit to an experimental calibration plot for a monolayer of glucose oxidase attached to a self‐assembled monolayer. The model showed the response was highly dependent on the amount of enzyme immobilized and therefore the reproducibility of monolayer enzyme electrodes will be limited by the reproducibility of the enzyme immobilization. The model predicts the response of the monolayer biosensor is limited by the turnover rate of the enzyme rather than the supply of substrate as is the case with thick‐film biosensors.

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Redox enzyme linked electrochemical sensors: Theory meets practice

Cited by 60 publications

References 103 publications

Parameters Important in Fabricating Enzyme Electrodes Using Self-Assembled Monolayers of Alkanethiols

Parameters Important in Fabricating Enzyme Electrodes Using Self-Assembled Monolayers of Alkanethiols

A Portable Fill‐and‐Flow Channel Biosensor with an Electrode to Predict the Effect of Interferences

From Thick Films to Monolayer Recognition Layers in Amperometric Enzyme Electrodes

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