Bipolar Electrode System Research Articles

Closed Bipolar Electrode Array for On-Chip Analysis of Cellular Respiration by Cell Aggregates

Cell aggregates have attracted much attention owing to their potential applications in tissue engineering and drug screening. To evaluate cellular respiration of individual cell aggregates in these applications, noninvasive and on-chip high-throughput analytical tools are necessary. Electrochemical methods for detecting oxygen concentrations are useful because of their noninvasiveness. However, these conventional methods may be unsuitable for high-throughput detection because it is difficult to prepare many electrodes on a small chip owing to the limitation of area for connecting electrodes. Alternatively, a bipolar electrode (BPE) system offers clear advantages. In this system, electrochemical reactions are induced at both ends of a BPE without complex wiring. In this study, we present a BPE array for detecting the respiratory activity of cell aggregates. Oxygen concentrations near cell aggregates at cathodic poles of BPEs were converted to electrochemiluminescence (ECL) signals of [Ru(bpy)3]2+/tripropylamine at anodic poles of BPEs. To separate ECL chemicals from cell aggregates, we fabricated a closed BPE device containing analytical and reporter chambers. As a proof of concept, 32 BPEs were controlled wirelessly using a pair of driving electrodes, and the respiratory activities of individual MCF-7 cell aggregates as a cancer model were successfully detected by monitoring ECL signals. Compared with conventional electrode arrays for cell analysis, the wiring of the current device was simple because the multiple BPEs functioned with only a single power supply. To the best of our knowledge, this is the first study of on-chip analysis of cellular activity using a BPE system.

Implementation of a Chloride‐selective Electrode Into a Closed Bipolar Electrode System with Fluorimetric Readout

AbstractApplicability of a bipolar electrode system was tested for arrangements containing a typical ion‐selective electrode (ISE) connected with an electrode coated by a conducting polymer characterized by electroluminescence. In this case a selective response of the ISE membrane at one pole of the bipolar electrode is transduced to a fluorimetric signal obtained by reduction of the conducting polymer at the second pole. This signal transformation mode was studied on example of a simple closed bipolar electrode system composed of all‐solid‐state chloride‐selective electrode with polypyrrole transducer as the sensing pole and the reporting pole represented by electrode coated by poly(3‐octylthiophene) (POT) layer characterized by fluorescence in the neutral state. In this system selective and linear dependences of fluorimetric signal on logarithm of chloride ions concentration in turn‐on mode were recorded for optimized external voltage applied. Alternatively, a concept of cascade bipolar electrode system with incorporation of additional bipolar electrode being a polarization source for the sensing bipolar electrode with ISE and POT layer was also tested. A significant advantage of the cascade system is its possibility to work spontaneously without external polarization. For this case also linear calibration plots of fluorimetric signal vs. logarithm of analyte concentration were recorded.

Asymmetrical electrode system for stable operation of a large-scale reverse electrodialysis (RED) system

To suppress inorganic scaling around the cathode in reverse electrodialysis, we suggest a bipolar membrane-containing asymmetric electrode system without significant power loss.

Discharging behavior of confined bipolar electrodes: Coupled electrokinetic and electrochemical dynamics

In this study we numerically investigate the intimately coupled transient electrokinetic and electrochemical dynamics of a nanoconfined bipolar electrode system, using experimental results to guide our analysis. Our recently developed 2D numerical model implements the Poisson-Nernst-Planck-Stokes system of equations to describe nanoscale chemical species transport by advection, migration, and diffusion, as well as the presence of both homogenous and heterogeneous reactions. By eschewing the assumption of electroneutrality and resolving diffuse-charge screening effects, our model uniquely accounts for a wide range of nonlinear transient effects including bipolar electrode (BPE) surface polarization, Faradaic charge accumulation, induced-charge electroosmotic flow, and ion concentration polarization. Using this model, we demonstrate that upon the removal of a polarizing electric field, excess accumulated charge at a BPE surface electrochemically discharges following the capacitive relaxation of diffuse space charge in the electrical double layers (EDLs) surrounding the BPE extremities. These EDLs continue to polarize the BPE as they relax by a process of drift-diffusion, wherein the counter-ionic space charge at each pole promotes a large influx of oppositely charged ions to restore electroneutrality. We numerically reproduced this electrokinetic enhancement effect that was first observed in a recently reported experimental system in which charged fluorophores were used as tracer molecules. Our results also support experimental evidence that, following capacitive EDL relaxation, nanoconfined BPEs can exhibit pseudocapacitance-like discharging behavior that is localized to a single end of the electrode; we experimentally linked this localization to surface oxidation of the anodic BPE pole under the applied field. In addition to providing important insight into the interplay between nanoscale electrokinetic and electrochemical phenomena that govern transient electrode processes, our model and the results presented in this work reinforce the notion that the domain of bipolar electrochemistry constitutes a promising frontier for developing “wirelessly” tunable charge storage and visual detection approaches which exploit both electrokinetic and Faradaic mechanisms.

Enhanced Visual Wireless Electrochemiluminescence Immunosensing of Prostate-Specific Antigen Based on the Luminol Loaded into MIL-53(Fe)-NH2 Accelerator and Hydrogen Evolution Reaction Mediation.

A sensitive prostate-specific antigen (PSA) detection method using a visual-readout closed bipolar electrode (BPE) system has been introduced by integration of hydrogen evolution reaction (HER) in cathodic pole and electrochemiluminescence (ECL) of luminol loaded within the MIL-53(Fe)-NH2 (L@MIL-53(Fe)-NH2) in the anodic pole. The cathode of the BPE was electrochemically synthesized by 3D porous copper foam, followed by decorating with nitrogen-doped graphene nanosheet and ruthenium nanoparticles. As an alternative, we employed carboxylate-modified magnetic nanoparticles (MNPs) for immobilization of the primary antibody (Ab1) and utilized the L@MIL-53(Fe)-NH2 conjugated to secondary antibody (Ab2) as a signaling probe and coreaction accelerator. After sandwiching the target PSA between Ab1 and Ab2, the MNP/Ab1-PSA-Ab2/L@MIL-53(Fe) were introduced to a gold anodic BPE. Finally, the resulting ECL of luminol and H2O2 at the anodic poles was monitored using a photomultiplier tube (PMT) or digital camera. The PMT and visual (camera)-based detections showed linear responses from 1 pg mL-1 to 300 ng mL-1 (limit of detection 0.2 pg mL-1) and 5 pg mL-1 to 200 ng mL-1 (limit of detection 0.1 pg mL-1), respectively. This strategy provides an effective method for high-performance bioanalysis and opens a new door toward the development of the highly sensitive and user-friendly device.

Modeling Faradaic Reactions and Electrokinetic Phenomena at a Nanochannel-Confined Bipolar Electrode

We present the most comprehensive two-dimensional numerical model to date for a nanoconfined bipolar electrochemical system. By accounting for the compact Stern layer and resolving the diffuse part of the electrical double layer at the bipolar electrode (BPE) surface and channel walls, our model captures the impact of surface polarization and ionic charge-screening effects on the heterogeneous charge-transfer kinetics, as well as nonlinear electrokinetic transport phenomena such as induced-charge electroosmosis and concentration polarization. We employ the Poisson-Nernst-Planck and Stokes flow system of equations, unified with generalized Frumkin-Butler-Volmer reaction kinetics, to describe water electrolysis reactions and the resulting transport of ions and dissolved gases in the confined BPE system. Our results demonstrate that under a sufficiently large applied electric field, the rapid reaction kinetics on our Pt BPE dynamically transition from charge-transfer-limited to mass-transfer-limited temporal regimes as regions depleted of redox species form and propagate outward from the respective BPE poles. This phenomenon was visualized experimentally with a pH-sensitive fluorescein dye and showed excellent phenomenological agreement with our numerical calculations, providing a foundation for further understanding and developing bipolar electrochemical processes in confined geometries. We introduce two prospective applications arising from our work: (1) a hybrid hydrodynamic/electrochemical peristaltic pump and (2) deducing information about chemical kinetics through simulation.

Development of a Split Bipolar Electrode System for Electrochemical Fluorination of Triphenylmethane

AbstractTo overcome the problem of electrochemical fluorination methods using a large amount of supporting electrolytes and fluorine sources, we employed a split bipolar electrode (s‐BPE) system, in which electrode reactions occur in a low concentration of supporting electrolyte and electricity is monitored. We optimized the electrochemical parameters for the s‐BPE system using a U‐shaped electrochemical cell and investigated the electrochemical fluorination of triphenylmethane as a model substrate in the presence of potassium fluoride (KF) or cesium fluoride (CsF) as a supporting electrolyte and a fluorine source dissolved by the help of poly(ethylene glycol) (PEG) additive. The fluorination of triphenylphoshine was also examined under the optimized conditions.

Percutaneous Radiofrequency Ablation of Spinal Osteoid Osteomas Using a Targeted Navigational Bipolar Electrode System.

Safe and effective percutaneous CT-guided radiofrequency ablation of spinal osteoid osteomas can be performed using a targeted navigational bipolar electrode system. Articulating bipolar electrodes with built-in thermocouples along an electrode shaft and variable generator wattage settings allow optimal nidus access, particularly in challenging locations; provide precise real-time monitoring of ablation zone volume and geometry; and minimize the risk of undesired thermal injury.

Direct Observation of Oxidation Reaction via Closed Bipolar Electrode-Anodic Electrochemiluminescence Protocol: Structural Property and Sensing Applications.

In this work, we developed an innovative closed bipolar electrode (BPE)-electrochemiluminescence (ECL) sensing strategy with generality for target detection. Based on charge balance and 100% current efficiency between the closed BPE poles and the driving electrodes, one of the driving electrodes in one cell of the closed BPE system was employed as ECL sensing surface to reflect the target on the BPE pole in the opposite cell. Compared with traditional BPE-ECL sensing method, which in general adopted the anodic ECL reagents such as Ru(bpy)32+ and its coreactant on one pole (anode) to reflect the target (occurring reduction reaction) on the other pole (cathode), the difference was that the targets occurring oxidation reaction could be detected by the anodic ECL reagents based on this strategy. To verify the feasibility of this strategy, the detection principle was stated first, and Fe(CN)64- as model target at anodic BPE pole were detected by anodic ECL reagents (Ru(bpy)32+ and TprA) on the driving electrode first. The ECL signals showed good performance for target detection. By changing the size and the material of the BPE pole where the targets were located, the detection of l-ascorbic acid (AA), uric acid (UA), and dopamine (DA) as other model targets with higher detection limit were accomplished. Visual and high-throughput detection of AA, UA, and DA were also successfully realized by an array of the closed BPE system. This closed BPE (array) system is an effective supplement of traditional BPE-ECL sensing and could greatly expand the scope of the detection target.

High-efficient preparation and screening of electrocatalysts using a closed bipolar electrode array system

High-efficient preparation and screening of electrocatalysts for oxygen reduction reaction (ORR) was realized by a three electrode driving closed bipolar electrode (BPE) array system. As high concentrations of Fe(CN)63−/4− (both 200 mM) existed in the anodic cell of the BPE system and same electrode material was adopted by the BPE anodic pole and driving electrode in anodic cell, the anodic cell performed similar to “good conductor” and the electrochemical behavior of the closed BPE system approximately equal to that of the three-electrode system in cathodic cell. Based on the above property and the parallel array, electrocatalysts containing bimetallic Pt Au and reduced graphene oxide (PtAu-rGO) with varying metal proportion were successfully prepared on the cathodic BPE poles by a two-step reduction process. Graphene oxide was firstly reduced to reduced graphene oxide (rGO) in each cathodic pole by cyclic voltammetry, and then Pt Au with different metal proportion were electrodeposited on the surface of rGO. Afterward, in-situ and high-throughput screening of these electrocatalysts for ORR was carried out based on the electrochemiluminescence (ECL) imaging on the corresponding anodic BPE poles. The screening results were consistent with those of the conventional electrochemical method by testing the catalytic performance one by one very well. This closed BPE array system with one potentiostat not only can prepare multiple catalyst candidates at the same time, but also can evaluate them, simultaneously, which is of great immediate significance to the field of fuel cell.

Spinal Osteoid Osteoma: Percutaneous Radiofrequency Ablation Using a Navigational Bipolar Electrode System.

The purpose of this article is to describe the use of a navigational bipolar radiofrequency ablation system for the treatment of spinal osteoid osteomas. Safe and effective imaging-guided percutaneous radiofrequency ablation of spinal osteomas can be performed using a multidirectional bipolar electrode system.

Electrochemiluminescence detection of human breast cancer cells using aptamer modified bipolar electrode mounted into 3D printed microchannel

In the present manuscript, a closed bipolar electrode system integrated with electrochemiluminescence (ECL) detection has been introduced for sensitive diagnosis of human breast cancer cells (MCF-7). For sensitive and selective detection, the anodic pole of the bipolar electrode was modified with the AS1411 aptamer, a specific aptamer for the nucleolin, and treated by the secondary aptamer modified gold nanoparticles. The electrochemiluminescence of luminol was followed in the presence of hydrogen peroxide on the anode pole of bipolar electrode (BPE) as an analytical signal. Moreover, 3D printed microchannels were used for the fabrication of BPE systems to minimize the required amounts of sample. The present aptasensor offers low cost, sensitive and selective cancer cell detection with two acceptable linear ranges. The first linear section appears within 10–100 cells and the latter is found to be within 100–700 cells. The limit of detection was about 10 cells.

Fluorimetric readout of ion-selective electrode potential changes

A novel method of quantitative optical readout of potentiometric responses of ion-selective electrodes is proposed. This idea was realized in a simple self-powered bipolar electrode system, with an ion-selective pole directly connected with the second pole, where a fluorimetric signal is generated. In this way, space and time separated optical readout and sampling can be achieved.This concept was tested on a model example of a system containing potassium-selective electrode (ISE-K) with polypyrrole solid contact, connected to a zinc wire immersed in the solution. In this arrangement increase of potassium ions activity in the solution results in change of the membrane potential of ISE-K, inducing reduction of polypyrrole solid contact and corresponding oxidation of the other component - zinc. Increase of zinc ions concentration is read as increase of emission intensity. Thus, this simple system allows quantitative in situ potassium ions determination, with the fluorescence intensity being a linear function of logarithm of analyte activity in solution in turn-on mode.Moreover, due to simplicity of the system and presence of reactants in the solution phase, a quantitative correlation between electrochemical and optical behaviour was confirmed and indications for the system optimization could be proposed.

Closed bipolar electrode system for a liquid-junction-free reference electrode integrated in an amperometric probe sensor

Reference electrodes (REs) play an essential role in electrochemical measurements. REs require liquid junctions to allow for ion conductivity between the RE and the sample solution. However, a liquid junction causes unwanted ion leakage into the analyte and clogging inducing reference potential inaccuracy. In this study, we report a liquid-junction-free amperometric probe sensor with an integrated RE, based on a closed bipolar electrode (cBPE) system. The liquid junction of the RE was replaced by the cBPE, which provides electrical conductivity instead of ionic conductivity between the inner solution of the RE and the sample solution. Since the solutions were in two separate cells, undesired contamination was completely prevented. We successfully conducted voltammetric and amperometric quantitative detection of 0.1–0.5 mM ferrocenemethanol using this system. Although its uses are limited, the present probe sensor with integrated liquid-junction-free reference electrode provides a feasible alternative for amperometric electrochemical measurements.

Electrochemical treatment of bio-treated landfill leachate: Influence of electrode arrangement, potential, and characteristics

The integration of electrocoagulation and electrooxidation process was employed to treat residual organic pollutants, ammonia, and total phosphorus for bio-treated landfill leachate. Electrochemical processes with dimensional stable anode, iron electrode and graphite felt cathode were studied under different electrode arrangement of bipolar electrode, dual anodes, and monopolar anode systems. Their performance for removal of pollutants and characteristics of the precipitates was evaluated. The effects of applied voltage from 7 V to 14 V, flow direction, and contents of suspended solids on removal performance were investigated. The best performance of simultaneous removal was recorded at the bipolar system, with the removal efficiency of 65%, 100%, and 91% for organic pollutants, ammonia, and phosphorus at 1.5 Ah L−1. The fluorophore distributions in the fractions of organic pollutants revealed that humic and fulvic acid-like substances were removed after the bipolar electrode process. Different compositions of Fe and O identified as FeO(OH) and γ-Fe2O3 were found in precipitates generated in bipolar and dual electrodes system. An applied voltage of 10 V and the cathode inflow mode facilitated the simultaneous removal process. Suspended solids served as the core of colloidal coagulant, was of great importance in integrated process to remove organic pollutants, but had no obvious effect to remove ammonia. These results indicate that this integrated bipolar system is an efficient approach for the treatment of residual pollutants from a bio-treated landfill leachate.

Hysteroscopic Endometrial Polypectomy: Clinical and Economic Data in Decision Making

Study ObjectiveTo compare the costs of hysteroscopic polypectomy using mechanical and electrosurgical systems in the hospital operating room and an office-based setting. DesignRetrospective cohort study (Canadian Task Force classification II-2). SettingTertiary referral hospital and center for gynecologic care. PatientsSeven hundred and fifty-four women who underwent endometrial polypectomy between January 20, 2015, and April 27, 2016. InterventionsHysteroscopic endometrial polypectomy performed in the same-day hospital setting or office setting using one of the following: bipolar electrode, loop electrode, mechanical device, or hysteroscopic tissue removal system. Measurements and Main ResultsThe various costs associated with the 2 clinical settings at Palagi Hospital, Florence, Italy were compiled, and a direct cost comparison was made using an activity-based cost-management system. The costs for using reusable loop electrode resection-16 or loop electrode resection-26 were significantly less expensive than using disposable loop electrode resection-27, the tissue removal system, or bipolar electrode resection (p = .0002). Total hospital costs for polypectomy with all systems were significantly less expensive in an office setting compared with same-day surgery in the hospital setting (p = .0001). Office-based hysteroscopic tissue removal was associated with shorter operative time compared with the other procedures (p = .0002) ConclusionThe total cost of hysteroscopic polypectomy is markedly higher when using disposable equipment compared with reusable equipment, both in the hospital operating room and the office setting. Same-day hospital or office-based surgery with reusable loop electrode resection is the most cost-effective approach in each settings, but requires experienced surgeons. Finally, the shorter surgical time should be taken into consideration for patients undergoing vaginal polypectomy in the office setting, owing more to patient comfort than to cost savings.

Low-voltage driven portable paper bipolar electrode-supported electrochemical sensing device

Aiming to overcome the obstacles of power supply requirement and chip usefulness in practice, a low-cost and convenient portable electrochemical sensing device is introduced for the first time, featuring bipolar electrode system, LED read-out, laminated paper-based devices, and low-voltage button cells. The electric circuits of this practical device are constructed on laminating films with copper and conductive carbon tapes, and the reservoirs facilitating chemical reactions are made with chromatography paper. The device is sensitive to electrochemical responses, validated by the demonstrative hydrogen peroxide and enzyme-assisted glucose detection. The business-card-size chip achieves sensitive analyte detection by naked eyes as well as further image processing in both laboratory samples and human serum samples testing, featuring detection limit as low as 1.79 μM and a dynamic range from 10 μM to 10 mM. This new practical design of point-of-care sensing chip entails the properties of facile fabrication, simple usage, high robustness, low power consumption, and accurate sensing showing the attainability of fabricating a useful and portable analytical device.

A resettable and reprogrammable keypad lock based on electrochromic Prussian blue films and biocatalysis of immobilized glucose oxidase in a bipolar electrode system

Herein, a resettable and reprogrammable biomolecular keypad lock on the basis of a closed bipolar electrode (BPE) system was established. In this system, one ITO electrode with immobilized chitosan (CS) and glucose oxidase (GOD), designated as CS-GOD, acted as one pole of BPE in the sensing cell; another ITO with electrodeposited Prussian blue (PB) films as the other pole in the reporting cell. The addition of ascorbic acid (AA) in the sensing cell with driving voltage (Vtot) at +2.5V would make the PB films become Prussian white (PW) in the reporting cell, accompanied by the color change from blue to nearly transparent. On the other hand, with the help of oxygen, the addition of glucose in the sensing cell with Vtot at −1.5V would induce PW back to PB. The change of color and the corresponding UV–vis absorbance at 700nm for the PB/PW films in the reporting cell could be reversibly switched by changing the solute in the sensing cell between AA and glucose and then switching Vtot between +2.5 and −1.5V. Based on these, a keypad lock was developed with AA, glucose and Vtot as 3 inputs, and the color change of the PB/PW films as the output. This keypad lock system combined enzymatic catalysis with bipolar electrochemistry, demonstrating some unique advantages such as good reprogrammability, easy resettability and visual readout by naked eye.

Bipolar Electrode Based Reversible Fluorescence Switch Using Prussian Blue/Au Nanoclusters Nanocomposite Film.

A highly efficient fluorescence switch system based on a closed bipolar electrode (C-BPE) system was proposed for the first time. Here, Au nanoclusters (Au NCs) were premodified on one pole of the BPE and acted as the fluorescent donor. On the basis of the spectral overlap between the absorbance of electrochromic material-Prussian blue (PB) and the fluorescence spectrum of Au NCs, fluorescence quenching ("off" state) induced by the inner filter effect was observed. Due to the electrochemical reversible redox reaction between PB and Prussian white, switching the polarity of driving voltage could easily achieve the fluorescence recovery of the Au NCs, corresponding to the "on" state. Through the reasonable design of C-BPE and optimization of driving voltage, the on-off ratio of the integrated fluorescence switch was up to 2.7 and a good fatigue resistance while performing 10 on-off cycles was obtained owing to the good stability of Au NCs and the reversible redox feature of PB. The introduction of BPE made the fluorescence switch more simple and controllable compared with the traditional three-electrode system, which will provide a new route for the design of the electrical-stimuli responsive fluorescence switch, especially for the integration of the miniaturized device.

Studying the thermal performance of a bipolar radiofrequency ablation with an improved electrode matrix system: In vitro experiments and modelling

Radiofrequency ablation (RFA) is becoming an effective treatment method for both primary tumors and tumors that have metastasized. Large tumors in difficult anatomic locations can be treated by RFA technologies. However, constant size and regular shape of damage zones cannot be obtained by recent RFA technologies. The aim of this study is to optimize the stability of RFA treatment by employing a newly proposed bipolar electrode system. A hepatic RFA mathematical model is developed by the finite element method approach. The model is validated with the experimental data. This model is then used to verify the reliability and stability of the proposed electrode system. Simulated results showed the cross section of the ablation zone utilizing designed electrode system approximates a square. In addition, the fraction of the necrosed tissue with this electrode pattern turned out to be larger than the fraction with single-probe RFA techniques. This system demonstrated higher ablation stability even for tissue regions that are close to blood vessels. The proposed electrode system is better suited for matrix-type RFA.