Comparison of the Effects of Biofouling on Voltammetric and Potentiometric Measurements

Kuhlmann, Julia; Dzugan, Laura C.; Heineman, William R.

doi:10.1002/elan.201200194

Cited by 23 publications

(26 citation statements)

References 20 publications

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“…The y-intercept of 146 mV vs. Ag/AgCl reference electrode in 0.1 M KCl agrees with the expected value of 142 mV for the formal potential of the ferricyanide-ferrocyanide redox couple [ 7 ]. We and others have observed similar results for this standard redox system [ 65 , 67 ].…”

Section: Resultssupporting

confidence: 86%

Potentiometric Biosensing of Ascorbic Acid, Uric Acid, and Cysteine in Microliter Volumes Using Miniaturized Nanoporous Gold Electrodes

et al. 2020

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Potentiometric redox sensing is a relatively inexpensive and passive approach to evaluate the overall redox state of complex biological and environmental solutions. The ability to make such measurements in ultra-small volumes using high surface area, nanoporous electrodes is of particular importance as such electrodes can improve the rates of electron transfer and reduce the effects of biofouling on the electrochemical signal. This work focuses on the fabrication of miniaturized nanoporous gold (NPG) electrodes with a high surface area and a small footprint for the potentiometric redox sensing of three biologically relevant redox molecules (ascorbic acid, uric acid, and cysteine) in microliter volumes. The NPG electrodes were inexpensively made by attaching a nanoporous gold leaf prepared by dealloying 12K gold in nitric acid to a modified glass capillary (1.5 mm id) and establishing an electrode connection with copper tape. The surface area of the electrodes was ~1.5 cm2, providing a roughness factor of ~16 relative to the geometric area of 0.09 cm2. Scanning electron microscopy confirmed the nanoporous framework. A linear dependence between the open-circuit potential (OCP) and the logarithm of concentration (e.g., Nernstian-like behavior) was obtained for all three redox molecules in 100 μL buffered solutions. As a first step towards understanding a real system, the response associated with changing the concentration of one redox species in the presence of the other two was examined. These results show that at NPG, the redox potential of a solution containing biologically relevant concentrations of ascorbic acid, uric acid, and cysteine is strongly influenced by ascorbic acid. Such information is important for the measurement of redox potentials in complex biological solutions.

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Section: Resultssupporting

confidence: 86%

Potentiometric Biosensing of Ascorbic Acid, Uric Acid, and Cysteine in Microliter Volumes Using Miniaturized Nanoporous Gold Electrodes

et al. 2020

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“…This result indicates that potentiometric measurements are perhaps much more sensitive to the effects of biofouling than what was first suggested. 23 On NPG, however, the slope does not decrease and no loss in sensitivity was observed. The slope is in agreement with the theoretical value of −59.2 mV, regardless of the concentration of the redox molecules in solution.…”

Section: Resultsmentioning

confidence: 90%

“…14,24 To evaluate the impact of biofouling in more detail, we examined the potentiometric and voltammetric response of dilute solutions of a poised redox system consisting of potassium ferri/ferrocyanide (0.2, 0.1, 0.075 mM) at both planar gold and nanoporous gold electrodes purposely biofouled by exposure to fibrinogen. 20,23 The potentiometric response was also examined using an unpoised redox system containing only ascorbic acid. In both cases, comparisons were made to clean electrodes not exposed to fibrinogen.…”

Section: Resultsmentioning

confidence: 99%

“…20 What is interesting, however, is that at this concentration, the potentiometric response at the two electrodes is nearly identical even though CV shows significant differences as previously noted. 23 To evaluate the response of the electrodes at low concentrations, the experiments were repeated using 0.1 mM and 0.075 mM [Fe(CN) 6 ] 3− solutions. Again, both biofouled and non-biofouled electrodes were examined.…”

Section: Resultsmentioning

confidence: 99%

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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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“…Two simple potentiometric sensors were used to monitor the biodegradation of the Mg samples by measuring the pH and the dissolved H 2 . Biofouling was not expected to affect the sensors during the exposure to the protein containing solutions since potentiometric measurements are not dependent on the surface area of the electrodes . The pH was monitored with a rugged and inexpensive micro glass electrode that was calibrated before and after the immersion tests using standard pH buffer solutions.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Sensors Continuously Monitor Magnesium Biodegradation under Cell Culture Conditions

et al. 2017

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Magnesium (Mg) and its alloys have increasingly been considered as implant materials for orthopedic, craniofacial, and cardiovascular applications. These materials generally have mechanical properties close to those of human bone and they biodegrade in aqueous environments. The biodegradation properties can be tailored to fit the desired application by changing the alloying elements and/or by addition of surface coatings. To test and compare the biodegradation properties of different materials, immersion tests in solutions ranging from simple salt solutions to complex biological media are commonly done that yield some information about the biodegradation rate and the biodegradation products on the surface after completion of the test. Here we report on a method that allows the continuous real‐time monitoring of the biodegradation process using electrochemical sensors for pH and H2 during immersion of Mg samples in the cell culture medium DMEM/F12 with different concentrations of fetal bovine serum and in the presence of living cells. The sensors effectively indicated the biodegradation behavior of Mg samples in real‐time. This system could be very useful for immersion tests and even supporting biocompatibility testing of implant materials.

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Comparison of the Effects of Biofouling on Voltammetric and Potentiometric Measurements

Cited by 23 publications

References 20 publications

Potentiometric Biosensing of Ascorbic Acid, Uric Acid, and Cysteine in Microliter Volumes Using Miniaturized Nanoporous Gold Electrodes

Potentiometric Biosensing of Ascorbic Acid, Uric Acid, and Cysteine in Microliter Volumes Using Miniaturized Nanoporous Gold Electrodes

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

Electrochemical Sensors Continuously Monitor Magnesium Biodegradation under Cell Culture Conditions

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