Studies of double layer capacitance and electron transfer at a gold electrode exposed to protein solutions

Moulton, Simon E.; Barisci, Joseph N.; Bath, A; Stella, Rita; Wallace, Gordon G.

doi:10.1016/j.electacta.2004.03.034

Cited by 90 publications

(94 citation statements)

References 32 publications

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“…Previous work has shown that albumin, fibrinogen, and other proteins adsorb very quickly on planar electrode surfaces. [25][26][27][28] Potentiometry of [Fe(CN) 6 Figure 1b, a linear plot was obtained yielding a slope of −59.8 mV, a y-intercept of 153 mV, and a linear regression coefficient of 0.997. The experimentally determined slope is nearly identical to the expected value of −59.2 mV for this one-electron redox couple at both planar and NPG electrodes.…”

Section: Resultsmentioning

confidence: 99%

Potentiometric Measurements in Biofouling Solutions: Comparison of Nanoporous Gold to Planar Gold

Farghaly

Lam

Freeman

et al. 2015

J. Electrochem. Soc.

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Potentiometric redox measurements were made in solutions of increasing biological complexity starting with buffer solutions containing either potassium ferri/ferrocyanide or ascorbic acid and finishing with plasma and blood. When the concentration of ferri/ferrocyanide was high (∼0.2 mM), both biofouled planar and nanoporous gold electrodes gave Nernstian slopes of 55-59 mV. However, at or below a critical concentration (≤ 0.1 mM), ∼20% loss in sensitivity was observed at planar gold in contrast to nanoporous gold where Nernstian behavior was retained. For ascorbic acid, a Nernst slope of −41 mV was observed at biofouled nanoporous gold electrodes. In contrast, biofouled planar gold electrodes failed to give any potentiometric redox response. At all concentrations studied, cyclic voltammetric measurements on biofouled electrodes revealed significant impairment of faradaic electroactivity at planar gold electrodes while no impairment was shown at nanoporous gold. These results indicate that nanoporous gold is an ideal electrode material to use when making both potentiometric and cyclic voltammetric measurements, particularly in complex solutions containing relatively low concentrations of redox molecules. As proof of concept, the redox potential of plasma and blood has been measured using nanoporous and planar gold electrodes and their values compared. Potentiometry is a technologically simple and inexpensive approach to obtain important information about the redox state of a system and/or the concentration of ions in solution.1,2 The measurement itself is simple in that all that is needed is a high impedance voltammeter, a stable reference electrode, and a suitable indicating electrode. In contrast to voltammetric measurements, no current flows, and the concentration of the redox species in solution does not change nor does the indicating electrode surface become altered as a potential is not applied. Likely the most popular potentiometric measurement is the measurement of pH using an ion-selective electrode that incorporates a thin membrane responsive to the activity of protons in solution. 3For the work described herein, the indicating electrode is an inert metallic redox electrode that is purposely designed to be nonselective and will 'ideally' respond to all redox active species in solution able to exchange electrons with the metallic surface.1,2 When the indicator electrode is immersed in solution, it will equilibrate electrochemically with the dissolved redox species and a potential will develop at its surface. The measured potential is governed by factors such as (1) the redox species present, (2) their concentrations (activities), and (3) the rate of electron exchange with the electrode.2,4,5 Such redox measurements have been used to characterize the redox state of solutions with a complex matrix including milk, cheese, sludge, water and biological systems. [6][7][8][9][10][11][12][13] An important and often neglected factor in the measurement of redox potential is the nature of the electrode surface, pa...

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Section: Resultsmentioning

confidence: 99%

Potentiometric Measurements in Biofouling Solutions: Comparison of Nanoporous Gold to Planar Gold

Farghaly

Lam

Freeman

et al. 2015

J. Electrochem. Soc.

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“…In contrast, PEDOT-pTS showed little effect from implantation lending to this polymer's being the best option of these polymers for use as a potential OCP-based neural electrode surface. These general features of reduced potential window, reduced Faradaic peak current, increased peak splitting, increased uncompensated resistance and increased charge transfer resistance on both SO 4 2-doped polymers and the Ppy-pTS are indicative of a fouling layer forming on the electrode surface, slowing or blocking electron transfer [46,47]. Fouling of an electrode surface should reduce electrode capacitance, therefore the slight increase in background capacitance seen on uncoated electrodes is most likely a visual artifact due to the higher uncompensated resistance or a pseudocapacitance (surface confined Faradaic reaction) such as a redox reaction of the adsorbed fouling layer.…”

Section: Discussionmentioning

confidence: 99%

Conducting polymer coated neural recording electrodes

et al. 2012

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Neural recording electrodes suffer from poor signal to noise ratio, charge density, biostability and biocompatibility. This paper investigates the ability of conducting polymer coated electrodes to record acute neural response in a systematic manner, allowing in depth comparison of electrochemical and electrophysiological response. Approach. Polypyrrole (Ppy) and poly-3,4-ethylenedioxythiophene (PEDOT) doped with sulphate (SO4) or para-toluene sulfonate (pTS) were used to coat iridium neural recording electrodes. Detailed electrochemical and electrophysiological investigations were undertaken to compare the effect of these materials on acute in vivo recording. Main results. A range of charge density and impedance responses were seen with each respectively doped conducting polymer. All coatings produced greater charge density than uncoated electrodes, while PEDOT-pTS, PEDOT-SO 4 and Ppy-SO4 possessed lower impedance values at 1 kHz than uncoated electrodes. Charge density increased with PEDOT-pTS thickness and impedance at 1 kHz was reduced with deposition times up to 45 s. Stable electrochemical response after acute implantation inferred biostability of PEDOT-pTS coated electrodes while other electrode materials had variable impedance and/or charge density after implantation indicative of a protein fouling layer forming on the electrode surface. Recording of neural response to white noise bursts after implantation of conducting polymer-coated electrodes into a rat model inferior colliculus showed a general decrease in background noise and increase in signal to noise ratio and spike count with reduced impedance at 1 kHz, regardless of the specific electrode coating, compared to uncoated electrodes. A 45 s PEDOT-pTS deposition time yielded the highest signal to noise ratio and spike count. Significance. A method for comparing recording electrode materials has been demonstrated with doped conducting polymers. PEDOT-pTS showed remarkable low fouling during acute implantation, inferring good biostability. Electrode impedance at 1 kHz was correlated with background noise and inversely correlated with signal to noise ratio and spike count, regardless of coating. These results collectively confirm a potential for improvement of neural electrode systems by coating with conducting polymers. 2013 IOP Publishing Ltd.

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“…The same group used EIS to study adsorption of a-lactoalbumin and b-casein on stainless steel [30]. Moulton et al [31] used EIS to monitor the adsorption of HSA and IgG on gold electrodes. In both instances, decreases in the double layer capacitance and increases in charge transfer resistance (R ct ) consistent with addition of insulating layers of proteins on the electrode surface were observed.…”

Section: Eis In Biomedical Engineeringmentioning

confidence: 98%

Impedance Spectroscopy: A Powerful Tool for Rapid Biomolecular Screening and Cell Culture Monitoring

2005

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Dielectric spectroscopy or Electrochemical impedance spectroscopy (EIS) is traditionally used in corrosion monitoring, coatings evaluation, batteries, and electrodeposition and semiconductor characterization. However, in recent years, it is gaining widespread application in biotechnology, tissue engineering, and characterization of biological cells, disease diagnosis and cell culture monitoring. This article discusses the principles and implementation of dielectric spectroscopy in these bioanalytical applications. It provides examples of EIS as label-free, mediator-free strategies for rapid screening of biocompatible surfaces, monitoring pathogenic bacteria, as well as the analysis of heterogeneous systems, especially biological cells and tissues. Descriptions are given of the application of nanoparticles to improve the analytical sensitivities in EIS. Specific examples are given of the detection of base pair mismatches in the DNA sequence of Hepatitis B disease, TaySachs disease and Microcystis spp. Others include the EIS detection of viable pathogenic bacteria and the influence of nanomaterials in enhancing biosensor performance. Expanding applications in tissue engineering such as adsorption of proteins onto thiolated hexa(-ethylene glycol)-terminated (EG6) self-assembled monolayer (SAM) are discussed.

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Studies of double layer capacitance and electron transfer at a gold electrode exposed to protein solutions

Cited by 90 publications

References 32 publications

Potentiometric Measurements in Biofouling Solutions: Comparison of Nanoporous Gold to Planar Gold

Potentiometric Measurements in Biofouling Solutions: Comparison of Nanoporous Gold to Planar Gold

Conducting polymer coated neural recording electrodes

Impedance Spectroscopy: A Powerful Tool for Rapid Biomolecular Screening and Cell Culture Monitoring

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