Design variations of a polymer–enzyme composite biosensor for glucose: Enhanced analyte sensitivity without increased oxygen dependence

McMahon, Colm P.; Killoran, Sarah J.; O’Neill, Robert

doi:10.1016/j.jelechem.2005.03.026

Cited by 47 publications

(90 citation statements)

References 69 publications

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“…On average, the J max value, and therefore enzyme loading, 41 for Pt D /GluOx/PPD was 15 times greater than for Pt C /GluOx/PPD. This is consistent with retention of a dome of enzyme solution around the disk tip as it is removed vertically from the GluOx Figure 2.…”

Section: Resultsmentioning

confidence: 87%

“…41 After rinsing and a settling period at +700 mV in fresh PBS, amperometric calibrations were carried out to determine the apparent Michaelis-Menten parameters (J max and K M (Glu); see below) and the linear region sensitivity (0-100 µM) of the biosensors to Glu and H 2 O 2 in quiescent air-saturated buffer, unless stated otherwise. All electropolymerizations and calibrations were performed in a standard three-electrode glass electrochemical cell containing 20 mL PBS at room temperature.…”

Section: Methodsmentioning

confidence: 99%

“…Substrate sensitivity of Pt/oxidase-PPD biosensors can be affected by the Pt geometry 40 and by the order of enzyme/polymer deposition on the Pt surface. 41 We therefore used biosensors fabricated from Pt disks and cylinders and GluOx immobilization before and after electrosynthesis of the PPD to determine the oxygen profile of devices with different Glu sensitivities. These studies reveal that surface GluOx loading can be used to control biosensor oxygen dependence in a counterintuitive direction: higher loading led to lower sensitivity to oxygen in the linear range of Glu response.…”

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confidence: 99%

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Control of the Oxygen Dependence of an Implantable Polymer/Enzyme Composite Biosensor for Glutamate

et al. 2006

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Biosensors for glutamate (Glu) were fabricated from Teflon-coated Pt wire (cylinders and disks), modified with the enzyme glutamate oxidase (GluOx) and electrosynthesized polymer PPD, poly(o-phenylenediamine). The polymer/enzyme layer was deposited in two configurations: enzyme before polymer (GluOx/PPD) and enzyme after polymer (PPD/GluOx). These four biosensor designs were characterized in terms of response time, limit of detection, Michaelis-Menten parameters for Glu (J max and K M (Glu)), sensitivity to Glu in the linear response region, and dependence on oxygen concentration, K M (O 2 ). Analysis showed that the two polymer/enzyme configurations behaved similarly on both cylinders and disks. Although the two geometries showed different behaviors, these differences could be explained in terms of higher enzyme loading density on the disks; in many analyses, the four designs behaved like a single population with a range of GluOx loading. Enzyme loading was the key to controlling the K M (O 2 ) values of these first generation biosensors. The counterintuitive, and beneficial, behavior that biosensors with higher GluOx loading displayed a lower oxygen dependence was explained in terms of the effects of enzyme loading on the affinity of GluOx for its anionic substrate. Some differences between the properties of surface immobilized GluOx and glucose oxidase are highlighted.L-Glutamate (Glu) is the most widespread excitatory neurotransmitter in the mammalian central nervous system, 1 plays a major role in a broad range of brain functions, and has been implicated in a number of neurological disorders. 2 Indeed, the development of devices for Glu detection has become an important research area due to the value of monitoring this key amino acid in a number of complex matrixes, including food processing, 3,4 cell cultures, 5-7 tissue slices ex vivo, 8,9 and intact brain in vivo. [10][11][12][13][14][15] A number of designs of biosensors for Glu monitoring have been reported and, although Glu receptors 16 Brain Res. Bull. 2002, 58, 401-404. (10) Burmeister, J. J.; Gerhardt, G. A. Trends Anal. Chem. 2003, 22, 498-502. (11)

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Section: Resultsmentioning

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Section: Methodsmentioning

confidence: 99%

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Control of the Oxygen Dependence of an Implantable Polymer/Enzyme Composite Biosensor for Glutamate

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“…These new determinations for Pt C are in line with other populations determined previously. 41,51 The similarity between the AA slopes for Pt C and Pt D electrodes demonstrates that neither subtle differences in the radial diffusion profiles for these two geometries nor the different condition of the metal surface (pristine cut for Pt D vs the Teflon-stripped origin of the Pt C cylinder; see Figure 1) 44,85 significantly affected AA sensitivity for the bare electrodes under the recording conditions used.…”

Section: Resultsmentioning

confidence: 96%

Contributions by a Novel Edge Effect to the Permselectivity of an Electrosynthesized Polymer for Microbiosensor Applications

et al. 2009

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Pt electrodes of different sizes (2 × 10 -5 -2 × 10 -2 cm 2 ) and geometries (disks and cylinders) were coated with the ultrathin non-conducting form of poly(o-phenylenediamine), PPD, using amperometric electrosynthesis. Analysis of the ascorbic acid (AA) and H 2 O 2 apparent permeabilities for these Pt/PPD sensors revealed that the PPD deposited near the electrode insulation (Teflon or glass edge) was not as effective as the bulk surface PPD for blocking AA access to the Pt substrate. This discovery impacts on the design of implantable biosensors where electrodeposited polymers, such as PPD, are commonly used as the permselective barrier to block electroactive interference by reducing agents present in the target medium. The undesirable "edge effect" was particularly marked for small disk electrodes which have a high edge density (ratio of PPDinsulation edge length to electrode area), but was essentially absent for cylinder electrodes with a length of >0.2 mm. Sample biosensors, with a configuration based on these findings (25 µm diameter Pt fiber cylinders) and designed for brain neurotransmitter L-glutamate, behaved well in vitro in terms of Glu sensitivity and AA blocking.The design of biosensors for implantation in functioning biological tissues is an important area of research with significant socioeconomic impact. 1-4 Depending on the target analyte, different signal transduction pathways have been exploited in the design of enzyme-based biosensors, including direct oxidation of reduced oxidases, 5-7 dehydrogenase chemistries, 8-10 redox mediators, 11-13 and spectrophotometric approaches. 14-16 However, "first generation" electrochemical biosensors, based on reactions 1-3, remain the most common design for many applications. 1,2,[17][18][19] The majority of these are oxidase-based devices designed to operate in amperometric mode, detecting H 2 O 2 generated by the reaction of the co-substrate (dioxygen) with the reduced form of the enzyme.First-generation biosensors in general, and especially those designed for tissue implantation, 20-24 must be capable of effective rejection of electroactive interference by endogenous reducing agents in the target medium because these devices are normally operated at a high applied overpotential for efficient H 2 O 2 * To whom correspondence should be addressed. E-mail: robert.oneill@ucd.ie.

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“…Different values of J max , determined under the same conditions, reflect differences in the amount of active enzyme on the surface, provided the sensitivity of the electrode to H 2 O 2 (reaction (3)) does not vary, as was the case for the PPDmodified Pt cylinders and disks used here. [33][34][35] …”

Section: Introductionmentioning

confidence: 99%

The efficiency of immobilised glutamate oxidase decreases with surface enzyme loading: an electrostatic effect, and reversal by a polycation significantly enhances biosensor sensitivity

McMahon

Rocchitta

Serra

et al. 2006

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The apparent Michaelis constant, K M , for glutamate oxidase (GluOx) immobilised on Pt electrodes increased systematically with enzyme loading. The effect was due, at least in part, to electrostatic repulsion between neighbouring oxidase molecules and the anionic substrate, glutamate (Glu). This understanding has allowed us to increase the Glu sensitivity of GluOxbased amperometric biosensors in the linear response region (100 ¡ 11 nA cm 22 mM 21 at pH 7.4; SD, n = 23) by incorporating a polycation (polyethyleneimine, PEI) to counterbalance the polyanionic protein. Differences in the behaviour of glucose biosensors of a similar configuration highlight a limitation of using glucose oxidase as a model enzyme in biosensor design.

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Design variations of a polymer–enzyme composite biosensor for glucose: Enhanced analyte sensitivity without increased oxygen dependence

Cited by 47 publications

References 69 publications

Control of the Oxygen Dependence of an Implantable Polymer/Enzyme Composite Biosensor for Glutamate

Control of the Oxygen Dependence of an Implantable Polymer/Enzyme Composite Biosensor for Glutamate

Contributions by a Novel Edge Effect to the Permselectivity of an Electrosynthesized Polymer for Microbiosensor Applications

The efficiency of immobilised glutamate oxidase decreases with surface enzyme loading: an electrostatic effect, and reversal by a polycation significantly enhances biosensor sensitivity

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