Cathodic Pole Research Articles

Electrocatalytically active and charged natural chalcopyrite for nitrate-contaminated wastewater purification extended to energy storage Zn-NO3− battery

Charged natural chalcopyrite (CuFeS2, Ncpy) was developed for a three-dimensional electrochemical nitrate reduction (3D ENO3−RR) system with carbon fiber cloth cathode and Ti/IrO2 anode and Zn-NO3− battery. The 3D ENO3−RR system with Ncpy particle electrodes (PEs) possessed superior nitrate removal of 95.6 % and N2 selectivity of 76 % with excellent reusability under a broad pH range of 2–13 involving heterogeneous and homogeneous radical mechanisms. The Zn-NO3− battery with Ncpy cathode delivered an open-circuit voltage of 1.03 V and a cycling stability over 210 h. It was found that Ncpy PEs functioned through self-oxidation, surface dynamic reconstruction (Cu1.02Fe1.0S1.72O1.66 to Cu0.61Fe1.0S0.27O2.98), intrinsic micro-electric field (CuI, S2− anodic and FeIII cathodic poles), and reactive species (•OH, SO4•−, 1O2, •O2− and •H) generation. Computational analyses reveal that CuFeS2(112) surface with the lowest surface energy preferentially exposes Fe and Cu atoms. Cu site is beneficial for reducing NO3− to NO2−, Fe and Fe−Cu dual sites are conducive to N2 selectivity, lowering the overall reaction barriers. It paves the way for selective NO3− reduction in wastewater treatment and can be further extended to energy storage devices by utilizing low-cost Ncpy.

Fe-single-atom catalysts boosting electrochemiluminescence via bipolar electrode integrated with its peroxidase-like activity for bioanalysis

Multifunctional single-atom catalysts (SACs) have been extensively investigated as outstanding signal amplifiers in bioanalysis field. Herein, a type of Fe single-atom catalysts with Fe-nitrogen coordination sites in nitrogen-doped carbon (Fe–N/C SACs) was synthesized and demonstrated to possess both catalase and peroxidase-like activity. Utilizing Fe–N/C SACs as dual signal amplifier, an efficient bipolar electrode (BPE)-based electrochemiluminescence (ECL) immunoassay was presented for determination of prostate-specific antigen (PSA). The cathode pole of the BPE-ECL platform modified with Fe–N/C SACs is served as the sensing side and luminol at the anode as signal output side. Fe–N/C SACs could catalyze decomposition of H2O2 via their high catalase-like activity and then increase the Faraday current, which can boost the ECL of luminol due to the electroneutrality in a closed BPE system. Meanwhile, in the presence of the target, glucose oxidase (GOx)-Au NPs-Ab2 was introduced through specific immunoreaction, which catalyzes the formation of H2O2. Subsequently, Fe–N/C SACs with peroxidase-like activity catalyze the reaction of H2O2 and 4-chloro-1-naphthol (4-CN) to generate insoluble precipitates, which hinders electron transfer and then inhibits the ECL at the anode. Thus, dual signal amplification of Fe–N/C SACs was achieved by increasing the initial ECL and inhibiting the ECL in the presence of target. The assay exhibits sensitive detection of PSA linearly from 1.0 pg/mL to 100 ng/mL with a detection limit of 0.62 pg/mL. The work demonstrated a new ECL enhancement strategy of SACs via BPE system and expands the application of SACs in bioanalysis field.

Potential Modulation and Control of Redox Reactions at Bipolar Electrodes Using an Ion-Selective Membrane

Potential difference at a bipolar electrode (BPE)/solution interface was controlled by forming a polymeric Na ion-selective membrane (ISM) on one part of the BPE. Using the difference between the potentials at the solution/cathodic pole and solution/anodic pole interfaces along with a predetermined driving voltage, the potential differences at the cathodic/anodic pole interface were independently regulated. For open bipolar systems, distinct changes in the intensity of electrochemiluminescence (ECL) were observed by varying the location of the ISM and/or the concentrations of the primary ions determining the potential of the ISM. Folded BPE structures with ISMs at one or both ends of the BPEs were more effective in changing the potential differences at the cathodic/anodic pole interface over a wider range. Furthermore, the potential control was efficient and changes in the ECL intensity were more significant in closed bipolar systems. The device was used for measuring analyte concentration by optimizing the size of the cathodic pole employed for detection and adjusting the driving voltage. We believe that the technique can be a starting point to achieve bipolar electrochemical devices with better controllabilities than those of previous bipolar electrochemical systems and similar reliabilities as those of three-electrode systems.

Wireless rotating bipolar electrochemiluminescence for enzymatic detection.

New dynamic, wireless and cost-effective analytical devices are developing rapidly in biochemical analysis. Here, we report on a remotely-controlled rotating electrochemiluminescence (ECL) sensing system for enzymatic detection of a model analyte, glucose, on both polarized sides of an iron wire acting as a bipolar electrode. The iron wire is controlled by double contactless mode, involving remote electric field polarization, and magnetic field-induced rotational motion. The former triggers the interfacial polarization of both extremities of the wire by bipolar electrochemistry, which generates ECL emission of the luminol derivative (L-012) with the enzymatically produced hydrogen peroxide in presence of glucose, at both anodic and cathodic poles, simultaneously. The latter generates a convective flow, leading to an increase in mass transfer and amplifying the corresponding ECL signals. Quantitative glucose detection in human serum samples is achieved. The ECL signals were found to be a linear function of the glucose concentration within the range of 10-1000 μM and with a limit of detection of 10 μM. The dynamic bipolar ECL system simultaneously generates light emissions at both anodic and cathodic poles for glucose detection, which can be further applied to biosensing and imaging in autonomous devices.

Cu-MOFs/GOx Bifunctional Probe-Based Synergistic Signal Amplification Strategy: Toward Highly Sensitive Closed Bipolar Electrochemiluminescence Immunoassay.

A closed bipolar electrochemiluminescence (BP-ECL) platform for sensitive prostate specific antigen (PSA) detection was proposed based on a novel synergistic signal amplification strategy. Specifically, glucose oxidase-loaded Cu-based metal-organic frameworks (Cu-MOFs/GOx) as bifunctional probes were bridged on the anodic interface with the target PSA as the intermediate unit. In virtue of the large loading capacity of Cu-MOFs, a large amount of a co-reactant, i.e., H2O2 in this L-012-based ECL system and gluconic acid were generated on the anodic pole in the presence of glucose. The generated gluconic acid could effectively degrade the Cu-MOFs to release Cu2+ which greatly accelerates the formation of highly active intermediates from co-reactant H2O2, boosting the ECL intensity. As for the cathodic pole, K3Fe(CN)6 with a lower reduction potential is used to reduce the driving voltage and speed up the reaction rate, further strengthening the ECL intensity. Thanks to the synergistic signal amplification effect at both two electrode poles of the BP-ECL system, highly sensitive detection of PSA was realized with a detection limit of 5.0 × 10-14 g/mL and a wide linear range of 1.0 × 10-13-1.0 × 10-7 g/mL. The strategy provides a novel way for signal amplification in the BP-ECL biosensing field.

Bioelectric Signaling: Role of Bioelectricity in Directional Cell Migration in Wound Healing.

In wound healing, individual cells' behaviors coordinate movement toward the wound center to restore small or large barrier defects. The migration of epithelial cells as a continuous sheet structure is one of the most important processes by which the skin barrier is restored. How such multicellular and tissue level movement is initiated upon injury, coordinated during healing, and stopped when wounds healed has been a research focus for decades. When skin is wounded, the compromised epithelial barrier generates endogenous electric fields (EFs), produced by ion channels and maintained by cell junctions. These EFs are present across wounds, with the cathodal pole at the wound center. Epithelial cells detect minute EFs and migrate directionally in response to electrical signals. It has long been postulated that the naturally occurring EFs facilitate wound healing by guiding cell migration. It is not until recently that experimental evidence has shown that large epithelial sheets of keratinocytes or corneal epithelial cells respond to applied EFs by collective directional migration. Although some of the mechanisms of the collective cell migration are similar to those used by isolated cells, there are unique mechanisms that govern the coordinated movement of the cohesive sheet. We will review the understanding of wound EFs and how epithelial cells and other cells important to wound healing respond to the electric signals individually as well as collectively. Mounting evidence suggests that wound bioelectrical signaling is an important mechanism in healing. Critical understanding and proper exploitation of this mechanism will be important for better wound healing and regeneration.

Recent Advances in Bipolar Electrochemiluminescence for Analytical Application

Background: Bipolar electrode (BPE), as an immersed electrical conductor in the electrolyte, can be polarized into cathodic and anodic poles under a sufficient electric field without direct contact, which affords a unique way to promote asymmetrical reactions at two poles. Up to date, bipolar electrochemistry has been widely used in the preparation of Janus materials, the fabrication of sensing/screening platform, target focusing and microswimmers. However, the wireless feature of BPE makes monitoring the Faradaic current difficult. Electrochemiluminescence (ECL), the light emission via an electrochemical reaction, matches the feature of bipolar electrochemistry well and is widely adopted to achieve the record of the Faradaic current flowing through the BPE. The objective of the present review aims to demonstrate the most recent advances in analytical applications (2016-2020) in combination with the high sensitive ECL as the output. Methods: Due to the difficulty of the recording of the Faradaic current flowing the BPE, the ECL, as a simple, sensitive and detectable signal-out, has become a popular method for analytical application based on the BPE. This review mainly summarizes the recent research of BPE/ECL according to the configuration and sensing principle of BPE designed in the ECL analysis. Results: Various sensors based on the BPE/ECL have been proposed for the electroactive targets and the bio-relevant molecules without the electroactivity by different ingenious designs. Besides, the microelectrode array and ultra-microelectrode (UME) array have also been applied in the BPE/ECL field to achieve the high temporal-spatial resolution imaging of the sample molecules based on the BPE microelectrode array. Conclusion: The combination of BPE and ECL provides a simple, portable and versatile sensor strategy for various targets due to the unique advantages of BPE and ECL, and can be applied for the fast, accurate and point-of-care diagnostics of numerous diseases. Though the BPE/ECL analysis has many merits such as high-throughput, excellent sensitivity, and high spatial-temporal resolution, the sensitive and commercial ECL analysis based on the BPE is still difficult to realize and the analysis research of BPE/ECL is still in the early stage.

Bipolar Electrode Arrays for Chemical Imaging and Multiplexed Sensing.

Bipolar electrodes (BPEs) with arrays of cathodic and anodic poles were developed for use in closed bipolar systems. To increase the number of BPEs in the array, the anodic and cathodic poles were connected with each other using thin leads. A further increase in the number of BPEs was achieved by forming the cathodic and anodic poles of the BPEs and the leads in different layers. A device with 9 × 10 arrays of cathodes and anodes was thus realized. When using this device to sense hydrogen peroxide (H2O2), the sensitivity and linear range of calibration plots could be adjusted by changing the driving voltage and the area ratio between the cathodic and anodic poles. The devices were used to image H2O2 and obtain time-lapse images for the diffusion and dilution of H2O2. Furthermore, DNA detection was demonstrated using an electroactive intercalator. The sensitivity could be improved by making the anodic poles smaller with respect to the cathodic pole and concentrating the electrochemiluminescence (ECL) in a small area. The ECL intensity changed according to the target DNA concentration in the solution.

Smartphone-Based Electrochemiluminescence for Visual Simultaneous Detection of RASSF1A and SLC5A8 Tumor Suppressor Gene Methylation in Thyroid Cancer Patient Plasma.

Visual one-step simultaneous detection of low-abundance methylation is a crucial challenge in early cancer diagnosis in a simple manner. Through the design of a closed split bipolar electrochemistry system (BE), detection of promoter methylation of tumor suppressor genes in papillary thyroid cancer, RASSF1A and SLC5A8, was achieved using electrochemiluminescence. For this purpose, electrochemiluminescence of luminol loaded into the Fe3O4@UiO-66 and gold nanorod-functionalized graphite-like carbon nitride nanosheet (AuNRs@C3N4 NS), separately, on the anodic and cathodic pole bipolar electrodes (BPEs) in two different chambers of a bipolar cell were recorded on a smartphone camera. To provide the same electric potential (ΔEelec) through the BPEs to conduct simultaneous light emission, as well as to achieve higher sensitivity, anodic and cathodic poles BPEs were separately connected to ruthenium nanoparticles electrodeposited on nitrogen-doped graphene-coated Cu foam (fCu/N-GN/RuNPs) to provide a hydrogen evolution reaction (HER) and polycatechol-modified reduced graphene oxide/pencil graphite electrode (PC-rGO/PGE) to provide electrooxidation of hydrazine. Moreover, taking advantages of the strong cathodic ECL activity due to the roles of AuNRs, as well as the high density of capture probes on the UiO-66 and Fe3O4 roles in improving the signal-to-background ratio (S/B) in complicated plasma media, a sensitive visual ECL immunosensor was developed to detect two different genes as model target analytes in patient plasma samples. The ability of discrimination of methylation levels as low as 0.01% and above 90% clinical sensitivity in thyroid cancer patient plasma implies that the present strategy is able to diagnose cancer early, as well as monitor responses of patients to therapeutic agents.

Control of Interfacial Potentials and Redox Reactions on Bipolar Electrodes Using Ag/AgCl

AbstractThe interfacial potential difference on the surface of bipolar electrodes was controlled by placing Ag/AgCl on part of the electrode. Oxygen reduction on the cathodic pole was coupled with an electrochemiluminescence (ECL) reaction on the anodic pole. In an open bipolar system, the ECL intensity depended on the location of Ag/AgCl and the concentration of Cl− ions. A current flowed through Ag/AgCl and the ratio of currents generated at the anodic and cathodic poles was affected by the position of Ag/AgCl. Further, the effect of Ag/AgCl placement was also demonstrated in a closed bipolar system using hydrogen peroxide (H2O2) and glucose as analytes. Ag/AgCl was also effective in adjusting the sensitivity to these analytes to achieve the best performance. This method of interfacial potential control is expected to contribute toward the development of reliable sensing devices and applications such as redox cycling, which require precise potential control.

DC bipolar anodization of aluminum: Wider anode area than expected on the bipolar electrodes

In this study, the electrical potential distributions on aluminum bipolar electrodes (BPEs) subjected to bipolar anodization in a direct current (DC) electric field were investigated. Aluminum sheets were used as BPEs, suspended in an electrolyte solution, and positioned either vertically or horizontally at the center of a cell. The results of reflective interference measurements, depth-profiling analysis, and re-anodization clearly revealed that the thicknesses of the porous alumina films and barrier layers near the aluminum substrates can be taken to represent the potential distributions on the horizontally located BPEs; the thickest anodic alumina was formed at the edge of the anodic pole of the BPE, and its thickness continuously decreased in the direction of the cathodic pole. Furthermore, the area of the anodic reaction was much larger than expected, accounting for 90% of the BPE.

Tyramide signal amplification and enzyme biocatalytic precipitation on closed bipolar electrode: Toward highly sensitive electrochemiluminescence immunoassay

Abstract A novel closed bipolar electrode-based electrochemiluminescence (BPE-ECL) imaging platform for visual detection of cardiac troponin I (cTnI) was constructed using tyramine signal amplification (TSA) strategy and enzyme-catalyzed precipitation techniques (BCP). In this platform, tyramine-HRP repeats formation and the BCP were executed on the cathodic pole in the presence of H2O2, which the ECL from Ru(bpy)32+/TPA system was used as signal reporter on the anodic pole. In the presence of cTnI, a large number of HRP from HRP-Au NPs-Ab compounds and tyramine-HRP repeats catalyze the formation of insoluble precipitation on the cathodic pole of the BPE, resulting in the decreased ECL from Ru(bpy)32+/TPA system on the anodic pole. Thanks to the TSA and BCP on the cathodic pole of the BPE platform, the method for cTnI detection exhibits the detection limits of 5.0 × 10−13 g/mL by a photomultiplier tube and 5.0 × 10-12 g/mL by a charge-coupled device imaging. Furthermore, the content of cTnI in human serum samples was determined and the recovery was between 90.0 % and 112.0 %. This multiple signal amplification strategy provides new perspectives for the BPE-ECL imaging platform in the biochemical analysis of biomarkers with low abundance.

Optimal design and experimental research of several-gigawatt multiple electron beam diode

The relativistic klystron amplifier (RKA) is one of the most efficient sources to amplify a high-power microwave signal due to its intrinsic merit of high-power conversion efficiency, high gain and stable operating frequency. However, the transverse dimensions of the RKA dramatically decrease when the operating frequency increases to X band, and the power capacity of the RKA is limited by the transverse dimensions. An X-band multiple-beam relativistic klystron amplifier is proposed to overcome the radiation power limitation. Each electron beam propagates in separate drift tubes and shares the same coaxial interaction cavities in the multiple-beam relativistic klystron amplifier, and the transverse dimensions of the multiple-beam relativistic klystron amplifier are free from the operating frequency restriction and a microwave power of over 1 GW is generated in the experiment. For a high-power electron device, the transmission of electron beam is critical, and the power conversion efficiency of the device is affected. In this paper, we conduct an investigation into the transmission process of the intense relativistic multiple electron beams, and the number of the multiple electron beams is set to be 16. It is found that when the multiple electron beam is transmitted in the device, the electron beam rotates around the center of the whole device, causing the electron beam to deviate from the drift tube channel. At the same time, each electron beam rotates around itself, and the cross section of the electron beam is deformed and expanded. In the improper design of electron beam and drift tube parameters, two kinds of rotating motions cause beam to lose. A multiple-electron-beam diode structure is optimized by the particle-in-cell simulation to reduce beam loss, with the effects of the related factors taken into account. Each pole of the cathodes is made up of graphite and stainless steel. The cathode head is made up of graphite, for the graphite has a lower emission threshold. The cathode base and cathode pole are made up of stainless steel, for the stainless steel has a higher emission threshold. Also the shape and structure of cathode pole, cathode head and anode are optimized to reduce the electric field intensity on the cathode pole and enhance the electric field intensity on the end face of cathode head. At the same time, the electric field distribution of the cathode head is uniform to improve the electron beam emission uniformity. The simulation results demonstrate that the transmission efficiency of multiple electron beams can reach 99%. In the experiment, the transmission efficiency of multiple electron beams is 92% with a beam voltage and beam current of 801 kV and 9.3 kA, respectively.

Control of Reactions on Bipolar Electrodes Using Ion-Selective Membranes

Bipolar electrochemistry is promising in realizing simultaneous multiplexed detection. In open bipolar systems, a potential gradient is formed in a solution. When an isolated electrode (bipolar electrode: BPE) that is not in contact with an external device is placed in the potential gradient, interfacial potential difference develops between the BPE and the solution (Figure 1A). As a result, oxidation and reduction reactions occur simultaneously on both poles (Figure 1B) [1]. The progress of the reduction reaction on the cathodic pole can be measured by coupling the reaction with a reaction that generates electrochemiluminescence (ECL) [2]. However, a problem with this method is that the interfacial potential difference on the BPE is not precisely controlled. In other words, the potential profile with respect to the electrode potential changes (Figure 1C). To solve this problem, we used an ion-selective membrane (ISM) on a part of the BPE. The ISM has an effect to fix the interfacial potential difference at the location without current generation through the interface (Figure 1D).Arrays of BPEs were formed with gold and Na+ ISM was formed on a part of each BPE. The surface of the BPE was insulated with a polyimide layer except for the anodic and cathodic poles and the active area of the ISM. To form the ISM, a layer of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT/PSS) was first coated on an exposed area of the BPE. The Na+ ISM was formed on the PEDOT/PSS layer. The solution to form the ISM contained 43.97 wt% polyvinyl chloride (PVC) dissolved in 1 mL tetrahydrofuran (THF). 53.38 wt% of nitrophenyl octyl ether (NPOE), 2.04 wt% of sodium ionophore X, and 0.61 wt% (w/w) of sodium tetrakis(4-fluorophenyl)borate (NaTFPB) were added to the PVC solution and mixed well. After forming the ISM, its peripheries were fixed with a silicone adhesive.In the experimental setup shown in Figure 1A, platinum wires (diameter: 0.5 mm) were used for the driving electrodes. The distance between the driving electrodes was 30 mm. To cause the ECL reaction, 10 mM phosphate buffer solution (pH 6.9) containing 5.0 mM tripropylamine (TPA) and 1.0 mM [Ru(bpy)3]2+ was used. Oxygen dissolved in the solution was used as an analyte. The experiments were conducted at 25°C.To control the potential of the BPEs, we previously used Ag/AgCl for the potential control. However, a problem was that current flowed through the non-polarizable metal/solution interface, affecting the ECL intensity. With regard to this, the ISM is superior because current does not flow. The effect of placing the ISM on a part of the BPE was first examined using BPEs of the same length and changing the location of the ISM (Figure 2). The ion selective electrode (ISE) was effective and the ECL intensity changed by changing the location of the ISE. The effect of the ISM was also demonstrated using folded double BPE structures with the ISM formed at either or both ends. Brighter ECL was observed with the folded structure compared with a single BPE. From these experiments, the effect of placing the ISM on BPEs was clearly observed. As an application to biosensing, we also tested the detection of glucose by immobilizing glucose oxidase and osmium polymer on the cathodic pole. The ECL was also observed accompanying the production of hydrogen peroxide by glucose oxidase and following the reduction of hydrogen peroxide.The effect of placing the ISM was also examined in closed bipolar systems. In the closed bipolar systems, solutions in the cathode and anode side are separated in different compartments. In this study, 15 mm-long electrodes were used and the electrodes extended in the two compartments. The anodic pole was exposed to the solution for ECL, whereas the cathodic pole was immersed in a Na2SO4 solution. A voltage (2.4 V) was applied between the driving electrodes immersed at the end of the solutions. The brightest ECL was observed on the BPE with the ISM nearest to the cathodic pole. The result indicates that the ISM is also effective in controlling the potential for closed bipolar systems.[1] S. E. Fosdick, K. N. Knust, K. Scida, R. M. Crooks. Bipolar electrochemistry. Angewandte Chemie International Edition, 52 (2013) 10438-10456. doi:10.1002/anie.201300947[2] K. F. Chow, F. Mavré, R. M. Crooks. Wireless electrochemical DNA microarray sensor. Journal of the American Chemical Society, 130 (2008) 7544-7545. doi:10.121/ja802013q Figure 1

Photochemical deposition of palladium nanoparticles on TiO2 nanoparticles and their application for electrocatalytic measurement of nitrate ions in potato, onion and cabbage using bipolar electrochemical method

A nanoparticle modified recordable digital versatile disc (DVD) blade was used as the bipolar electrode. The cathodic pole of the DVD blade was modified by TiO2 nanoparticles. Then, Pd nanoparticles were deposited at the TiO2NPs/DVD surface by photochemical method. In the proposed setup, when the required potential was applied by using a direct power supply, the nitrate ions are reduced electrocatalytic at the PdNPs/TiO2NPs cathodic pole and the oxidation reaction of the silver layer is performed at the anode pole of the bipolar electrode, simultaneously. The oxidation process led to the dissolution of the silver layer. The results show that the dissolution length of the silver layer on the surface of the anodic pole at constant interval time is proportional to the nitrate ion concentration in the analytical solution. Finally, this method was used to measure the concentration of nitrate ions in the various real samples and obtained satisfactory results.

A compact bipolar electrochemistry device utilizing a liquid free catholyte and eye visual indication of the reporting event for the determination of antioxidant capacity in real-world samples

Here we report for the first time the development of a compact, closed bipolar electrochemistry (BPE) device for the determination of antioxidant capacity in real-world samples by recording the onset driving voltage at which an eye-visible reporting event at the cathode pole of bipolar electrode (BE) occurs. The BPE cell consists of two distinct anode and cathode compartments that are electrically connected through a platinum wire BE. The anode pole of the BE is covered by a cellulose acetate thin film to prevent the fouling of the surface, while the cathode pole is embedded into an agarose hydrogel containing phenolphthalein, i.e., an acid-base indicator. The method relies on the oxidation of the reducing compounds in the sample by a fixed amount of H2O2 and the electro oxidation of the remaining H2O2 in the anode pole of the BE. This reaction triggers the reduction of water at the cathodic pole accompanied by the production of hydroxyl ions at different, H2O2 concentration-dependent onset driving voltages. The resulting increase of pH at the cathode pole results in the formation of a pink spot (reporting event), which is visible by the unaided eye. The applicability of the BPE device for the determination of antioxidant capacity in fruit juices and sodas is demonstrated. The analytical results, expressed as Trolox (TEAC) or Vitamin C (CVEAC) equivalent antioxidant capacity, correlate well with those obtained by the CUPRAC method.

P544Evaluation of three-dimensional trajectory of pacing cathode pole in coronary sinus to predict long-term response to cardiac resynchronization therapy

Abstract Background An automated method for 3D reconstruction of coronary sinus (CS) lead’s pacing cathode trajectory (3DTJ) was proposed to acutely predict long term left ventricular (LV) mechanic response to cardiac resynchronization therapy (CRT). Preliminary data showed that 3DTJ at biventricular pacing (BIV) start changed in CRT responders (R) to be, becoming less eccentric and more multi-directional, as described by the ratio between its two major axes (S1/S2). Purpose The TRAJECTORIES study (Trajectory Changes Of Coronary Sinus Lead Tip And Cardiac Resynchronization Therapy Outcome, NCT02340546) is an observational study by seven Italian centers about the prediction of CRT-induced LV reverse remodeling by means of the acute 3DTJ changes at CRT implant. Methods In CRT implants with standard indications, stable CHF and regular ventricular rhythm, a fluoroscopic sequence in two standard X-rays views of a few seconds was acquired immediately before (T-1) and after the start of BIV (T0). 3DTJ of CS lead cathode pole throughout the cardiac cycle at T-1 and T0 were reconstructed and analyzed. Changes of the ratio between its two major axes (S1/S2) between T-1 and T0 (ΔS1/S2), were compared with the volumetric response at six-month f.u: the percent negative variation of S1/S2 (ΔS1/S2 < 0), marking a more multi-directional shape of 3DTJ, was assumed to predict the response to CRT. Volumetric response was adjudicated by a core-lab using a cut-off reduction ≥ 15% in echocardiographic LV end-systolic volume at f.u.. Results Out of 119 patients enrolled in 42 months, 74 pts ended f.u. (55 m; age 69 ± 10) and 30 dropped–out. Patients baseline features were: ischemic heart disease (IHD) 34 /74 pts; sinus rhythm 64/74 pts; upgrade from PM/ICD 13/74 pts; QRS morphology with LBBB 57/74, intraventricular aspecific delay 6 and RV pace 11 pts; LV ejection fraction (EF) 30 ± 9%; QRS duration 162 ± 25 ms. At f.u., volumetric R were 45/74 (60%). Concordance between ΔS1/S2 (as either ΔS1/S2 < 0 or ΔS1/S2 > 0) and volumetric response was 77% overall (57/74), 82% in R (37/45), 69% in non-R (20/29). Non-concordant patients were mostly non-R: 52% vs 35% of non-R in concordant group, but no other differences were found. The proposed 3DTJ metric showed sensitivity = 72%, specificity =80%; positive predictive value = 69%, negative predictive value = 82%. Conclusions Metrics of 3DTJ can be useful to acutely predict CS pacing site-specific response to CRT in long-term, above all in R. 3DTJ assessment might highlight aspects of CRT effects on LV mechanics.

Control of Reactions on Bipolar Electrodes Using Ion-Selective Membranes

IntroductionBipolar electrochemistry is an attractive technique to realize simultaneous multiplexed detection. In bipolar electrochemical systems, a potential gradient is formed in a solution. When an isolated electrode (bipolar electrode: BPE) that is not in contact with an external device is placed in the potential gradient, potential difference is generated at the interface between the BPE and the solution (Figure 1(A)), which can be a motive force to make anodic and cathodic reactions to proceed on the BPE (Figure 1(B)) [1]. The progress of reduction reactions on the cathodic pole can be measured by coupling the reaction with electrochemiluminescence (ECL) [2]. Although the simple single electrode configuration is attractive in realizing a large array of BPEs, an issue is that the interfacial potential difference on the BPE is not controlled intentionally. In other words, the potential profile in the solution can vary as expressed by 1, 2, and 3, although the potential difference between the two poles is the same for all cases (Figure 1(C)). To solve this problem, we used an ion-selective membrane (ISM) on a part of the BPE. The ISM has an effect to fix the interfacial potential difference there without current generation through the interface (Figure 1(D)). Method Arrays of BPEs were formed with platinum (Pt) or gold (Au). An ISM was formed on a part of each BPE. The surface of the BPE was insulated with polyimide layer except for the anodic and cathodic poles and the active area of the ISM. We previously tested the use of thin-film Ag/AgCl instead of the ISM. However, a problem was that current flowed through the interface due to its non-polarized nature, affecting the ECL intensity. With regard to this, current does not flow through the ISM/solution interface. The location of the ISM was changed with BPEs of the same length (Figure 2(A)). Otherwise, BPEs of different lengths were fabricated, and the location of the ISM was kept constant between the ISM and the cathodic pole (Figure 2(B)).The active areas on the BPEs were cleaned and the cleanliness was checked by taking cyclic voltammograms (CV) in a solution containing 100 mM KCl and 10 mM K3[Fe(CN)6]. To form the ISM, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT/PSS) was first coated on an exposed area of the BPE. To form the ISM, 20 µl of Na+ ionophore cocktail containing 89.5% 2-Nitrophenyl octyl ether, 10.0% sodium ionophore II, and 0.5% sodium tetraphenylborate (w/w) (Sigma-Aldrich (Japan)) was dissolved in 79.3% polyvinyl chloride (PVC) and tetrahydrofuran (PVC/THF) solution. The solution was dropped onto the PEDOT/PSS layer to form the ISM and was dried.Figure 3 shows the setup used for the experiment. Pt wires (diameter: 0.5 mm) were used for the driving electrodes. The distance between the driving electrodes was 30 mm. For ECL, 10 mM PBS (pH 6.9) containing 5.0 mM tripropylamine (TPA) and 1.0 mM [Ru(bpy)3]2+ was used. As an analyte, oxygen dissolved in the solution was used. To change the interfacial potential difference at the ISM, Na+ ions of different concentrations were added to the solution. Before injecting the solution in the reaction chamber, the solution was stirred for at least 30 min to saturate air. Pictures of ECL were taken immediately after the application of the voltage with 60 s exposure. The experiments were conducted at 25°C. Results and Conclusions The potential of the ISM was checked using a BPE with an ISM by measuring the potential in NaCl solutions of various concentrations with respect to a commercial liquid junction Ag/AgCl electrode. Figure 4 shows the dependence of the potential of the ISE on the concentration of Na+ ions. The slope was 59.0 mV/decade, which was very close to the value expected from the Nernst equation. The effect of placing the ISM on a part of the BPE was investigated using BPEs of the same length. ECL intensity changed depending on the location of the ISM (Figure 5). Figure 6 shows ECL observed using BPEs of different length maintaining the distance between ISM and the cathodic pole. In both cases, the effect of placing the ISM was clearly observed and the ECL intensity was strongest when the distance between the ISM and the anodic pole is longer. These results indicate that the ECL intensity can actually be controlled by the ISM. We have tested other electrode configurations. The results will also be presented.The potential control developed in this study is also effective to control the electrode potentials in closed BPE systems in which solutions are separated in different compartments.

Coupling electrochemistry with a fluorescence reporting reaction enabled by bipolar electrochemistry

A bipolar electrochemistry setup for the sensitive indirect detection of redox active analytes by means of a fluorescence signal generated by the oxidation of dihydroresorufin is proposed. The redox conversion leads to the in situ and real time formation of the oxidized form resorufin, a highly fluorescent molecule. A photomultiplier tube is used for the detection of the emitted fluorescence light. The system was first characterized using the electrochemical reduction of [Fe(CN)6]3− as model analyte at the cathodic bipolar pole, promoting an increase in the fluorescence signal which is proportional to the concentration of [Fe(CN)6]3− in solution. Indirect quantification is enabled with a linear range between 10 μM and 50 μM and a limit of detection down to 0.2 μM. The system was successfully applied for the detection of glucose and hydrogen peroxide using enzyme modified electrodes at the detection pole. The use of a closed bipolar system allows translating the electrochemical redox process for analyte detection into a fluorescence reporting reaction, providing (bio)sensing capabilities with adequate sensitivity and the possibility for optically monitoring non-fluorogenic redox reactions.

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.