Multi Electrode Research Articles

A solar thermoelectric system by temperature difference for efficient removal of chromium (VI) in water and soil

In this work, we designed and developed a facile solar thermoelectric generator (STEG)-based system and a new electrokinetic remediation (EKR) system, which consists of main electrodes and unenergized auxiliary electrodes. The prepared nanocomposite was investigated for the effectiveness of the STEG+PANI-CNT/GF system in remediating Cr-contaminated. Photothermal performance test were applied in order to examine this STEG could export a power density of 365.56mW/dm2 and output potential of 801mV at the temperature difference of 50 ℃. Thus the STEG could be used as the power to construct a Cr(VI) removal system using polyaniline (PANI) film/carbon nanotubes (CNT) modified graphite felt (GF) electrode (PANI-CNT/GF) as cathode and graphite rod as anode. The as-prepared STEG+PANI-CNT/GF system exhibited a significant Cr(VI) removal efficiency (96.2% in water) through electromigration, electro-adsorption and electroreduction. Moreover, a multi auxiliary electrodes (AEs) system (STEG+PANI-CNT/GF+AEs) with six PANI-CNT/GF auxiliary electrodes was constructed in remediating Cr(VI)-contaminated soil, showing Cr(VI) removal efficiency of 16.7-60.1% higher than that of STEG+PANI-CNT/GF. The PANI-CNT/GF auxiliary electrodes could bind Cr(VI) and adjust electric field distribution, contributing to adsorption and reduction of Cr(VI). Consequently, this work provides a promoting approach for heavy metals removal in future application.

Impact of background input on memory consolidation

Memory consolidation involves repeated replay of new information by the hippocampus, which transfers memories to the neocortex for long-term storage. This occurs mainly during slow wave sleep, a phase characterized in the cortex by low cholinergic tone and low afferent input. High cholinergic tone has been shown to hamper memory consolidation, probably mediated by reduced network excitability (the ease of activity propagation in a network). We used cortical neuronal networks on multi electrode arrays to investigate whether low background input contributes to memory consolidation. Networks received focal electrical stimuli to memorize, with or without background afferent input (global optogenetic stimulation). Background stimulation hampered memory formation and consolidation, confirming the importance of low background input. Moreover, it lowered network excitability, similar to high cholinergic tone. These findings suggest that high network excitability is a critical feature of slow wave sleep that facilitates memory consolidation.

Immune response caused by M1 macrophages elicits atrial fibrillation-like phenotypes in coculture model with isogenic hiPSC-derived cardiomyocytes

BackgroundAtrial fibrillation has an estimated prevalence of 1.5–2%, making it the most common cardiac arrhythmia. The processes that cause and sustain the disease are still not completely understood. An association between atrial fibrillation and systemic, as well as local, inflammatory processes has been reported. However, the exact mechanisms underlying this association have not been established. While it is understood that inflammatory macrophages can influence cardiac electrophysiology, a direct, causative relationship to atrial fibrillation has not been described. This study investigated the pro-arrhythmic effects of activated M1 macrophages on human induced pluripotent stem cell (hiPSC)-derived atrial cardiomyocytes, to propose a mechanistic link between inflammation and atrial fibrillation.MethodsTwo hiPSC lines from healthy individuals were differentiated to atrial cardiomyocytes and M1 macrophages and integrated in an isogenic, pacing-free, atrial fibrillation-like coculture model. Electrophysiology characteristics of cocultures were analysed for beat rate irregularity, electrogram amplitude and conduction velocity using multi electrode arrays. Cocultures were additionally treated using glucocorticoids to suppress M1 inflammation. Bulk RNA sequencing was performed on coculture-isolated atrial cardiomyocytes and compared to meta-analyses of atrial fibrillation patient transcriptomes.ResultsMulti electrode array recordings revealed M1 to cause irregular beating and reduced electrogram amplitude. Conduction analysis further showed significantly lowered conduction homogeneity in M1 cocultures. Transcriptome sequencing revealed reduced expression of key cardiac genes such as SCN5A, KCNA5, ATP1A1, and GJA5 in the atrial cardiomyocytes. Meta-analysis of atrial fibrillation patient transcriptomes showed high correlation to the in vitro model. Treatment of the coculture with glucocorticoids showed reversal of phenotypes, including reduced beat irregularity, improved conduction, and reversed RNA expression profiles.ConclusionsThis study establishes a causal relationship between M1 activation and the development of subsequent atrial arrhythmia, documented as irregularity in spontaneous electrical activation in atrial cardiomyocytes cocultured with activated macrophages. Further, beat rate irregularity could be alleviated using glucocorticoids. Overall, these results point at macrophage-mediated inflammation as a potential AF induction mechanism and offer new targets for therapeutic development. The findings strongly support the relevance of the proposed hiPSC-derived coculture model and present it as a first of its kind disease model.

Abstract We023: P53 Activation Promotes Maturational Characteristics of Pluripotent Stem Cell-derived Cardiomyocytes in 3D Suspension Culture via FOXO-FOXM1 Regulation

Background: Current protocols can generate highly-pure populations of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in vitro that recapitulate key characteristics of mature in vivo cardiomyocytes. Yet, there exists a risk of arrhythmias when hiPSC-CMs are injected into large animal models. This prompts further investigation into the mechanisms of hiPSC-CM maturation to facilitate clinical translation. Hypothesis: The forkhead box (FOX) family of transcription factors can regulate maturation in neonatal cardiomyocytes through a balance between FOXO and FOXM1. We also previously found that p53 activation could enhance hiPSC-CM maturation. Therefore, we hypothesized that p53 activation increases FOXO and decreases FOXM1 to promote hiPSC-CM maturation in three-dimensional (3D) suspension culture. Methodology: 3D cultures of hiPSC-CMs were treated with Nutlin-3a (p53 activator), LOM612 (FOXO activator), AS1842856 (FOXO inhibitor), or RCM-1 (FOXM1 inhibitor), starting 2 days after onset of beating. The hiPSC-CMs were assessed for maturation in metabolic, contractile, and electrophysiological properties, by Seahorse mito stress test, Multi electrode array, and VALA kinetic image cytometer respectively. Results: P53 activation promoted FOXO upregulation and FOXM1 downregulation in hiPSC-CMs, measured by RT-qPCR and immunostaining. Alongside this, p53 activation also promoted hiPSC-CM metabolic and contractile maturational characteristics, seen by increase in oxygen consumption and beat amplitude respectively. FOXO inhibition significantly decreased expression of cardiac-specific markers such as TNNT2 and eliminated spontaneous beating. In contrast, FOXO activation or FOXM1 inhibition promoted maturational characteristics of hiPSC-CMs such as increase in contractility, oxygen consumption, and voltage peak maximum upstroke velocity. Further, by single-cell RNAseq, FOXO activated groups showed increase in cardiac maturational pathways compared against DMSO control groups. Conclusions: These results show that p53 activation promotes FOXO and suppresses FOXM1, which modulate hiPSC-CM maturation in 3D suspension. Our study expands current understanding of hiPSC-CM maturational mechanisms in a clinically-relevant 3D culture system.

Promotion of maturation of human pluripotent stem cell-derived cardiomyocytes via treatment with the peroxisome proliferator-activated receptor alpha agonist Fenofibrate.

As research on in vitro cardiotoxicity assessment and cardiac disease modeling becomes more important, the demand for human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) is increasing. However, it has been reported that differentiated hPSC-CMs are in a physiologically immature state compared to in vivo adult CMs. Since immaturity of hPSC-CMs can lead to poor drug response and loss of acquired heart disease modeling, various approaches have been attempted to promote maturation of CMs. Here, we confirm that peroxisome proliferator-activated receptor alpha (PPARα), one of the representative mechanisms of CM metabolism and cardioprotective effect also affects maturation of CMs. To upregulate PPARα expression, we treated hPSC-CMs with fenofibrate (Feno), a PPARα agonist used in clinical hyperlipidemia treatment, and demonstrated that the structure, mitochondria-mediated metabolism, and electrophysiology-based functions of hPSC-CMs were all mature. Furthermore, as a result of multi electrode array (MEA)-based cardiotoxicity evaluation between control and Feno groups according to treatment with arrhythmia-inducing drugs, drug response was similar in a dose-dependent manner. However, main parameters such as field potential duration, beat period, and spike amplitude were different between the 2 groups. Overall, these results emphasize that applying matured hPSC-CMs to the field of preclinical cardiotoxicity evaluation, which has become an essential procedure for new drug development, is necessary.

Multi Electrode Differential Voltage Sensor Based on Electric Field Coupling

With the increasing demand for electricity, voltage measurement has been applied in various fields of the power grid, especially in low-voltage distribution networks and household appliances. However, in low-voltage distribution networks, traditional contact measurement cannot be used due to technical limitations such as the need to damage the insulation layer. Non contact voltage measurement is becoming the main voltage measurement method, A major technical challenge in non-contact measurement is the interference of external electric fields. In order to solve the above problems, this article develops a new type of non-contact low-voltage measurement equipment, which can overcome the interference of external electric fields on measurement and achieve high-precision non-contact voltage measurement. The experimental results indicate that the sensor designed in this paper has high measurement accuracy. The ratio error at power frequency is within ± 0.9%, and the phase error is within 3°. In addition, the sensor also has the advantages of low cost, small size, and convenient manufacturing.

Production of continuous nanofiber bundles by multi parallel electrodes in needleless electrospinning

This study explores the collection of nanofiber bundles on a conveyor belt for continuous production, contrasting with previous studies that focused on the production of limited-length nanofibers directly on electrodes. The research focuses on examining how the plate width and the gap distance within a conveyor system influence the alignment and morphology of the nanofibers. To fully understand these effects, the designs of multi parallel electrodes were analyzed using COMSOL Multiphysics. This analysis focused on determining the electric field strength, the electrical potential, and the vectors of the electric field within these systems. Additionally, the study delved into the alignment and morphology of the polyacrylonitrile nanofibers, employing a field emission scanning electron microscope for detailed observation. The findings revealed that both the width of the plates and the gap distance critically impacted the alignment and nanofiber morphology. The optimal alignment and uniformity of nanofibers were achieved at specific plate widths and gap distances, demonstrating the intricate relationship between these parameters and nanofiber characteristics.

Characterization of human iPSC-derived sensory neurons and their functional assessment using multi electrode array

Sensory neurons are afferent neurons in sensory systems that convert stimuli and transmit information to the central nervous system as electrical signals. Primary afferent neurons that are affected by non-noxious and noxious stimuli are present in the dorsal root ganglia (DRG), and the DRG sensory neurons are used as an in vitro model of the nociceptive response. However, DRG derived from mouse or rat give a low yield of neurons, and they are difficult to culture. To help alleviate this problem, we characterized human induced pluripotent stem cell (hiPSC) derived sensory neurons. They can solve the problems of interspecies differences and supply stability. We investigated expressions of sensory neuron related proteins and genes, and drug responses by Multi-Electrode Array (MEA) to analyze the properties and functions of sensory neurons. They expressed nociceptor, mechanoreceptor and proprioceptor related genes and proteins. They constitute a heterogeneous population of their subclasses. We confirmed that they could respond to both noxious and non-noxious stimuli. We showed that histamine inhibitors reduced histamine-induced neuronal excitability. Furthermore, incubation with a ProTx-II and Nav1.7 inhibitor reduced the spontaneous neural activity in hiPSC-derived sensory neurons. Their responsiveness was different from each drug. We have demonstrated that hiPSC-derived sensory neurons combined with MEA are good candidates for drug discovery studies where DRG in vitro modeling is necessary.

Electrochemical treatment of wastewaters containing metal-organic complexes: A one-step approach for efficient metal complex decomposition and selective metal recovery

Metal-organic complexes, especially those of ethylenediaminetetraacetic acid (EDTA) with metals such as copper (Cu) and nickel (Ni) (denoted here as Cu-EDTA and Ni-EDTA), are common contaminants in wastewaters from chemical and plating industries. In this study, a multi-electrode (ME) system using a two-chamber reactor and two pairs of electrodes is proposed for simultaneous electrochemical oxidation of a wastewater containing both Cu-EDTA and Ni-EDTA complexes as well as separation and selective recovery of Cu and Ni onto two different cathodes via electrodeposition. Our results demonstrate that the ME system successfully achieved 90% EDTA removal, 99% solid Cu recovery at the Cu recovery cathode and 56% Ni recovery (33.3% on the Ni recovery cathode and 22.6% in the solution) after a four-hour operation. The system further achieved 85.5% Ni recovery after consecutive five cycles of operation for 20 h. While Cu removal was mainly driven by the direct reduction of EDTA-complexed Cu(II) at the cathode, oxidation of EDTA within the Ni-EDTA complex at the anode was a prerequisite for Ni removal. The oxidation of metal-bound EDTA and free EDTA was driven by •OH and direct electron transfer on the PbO2 anode surface and graphite anode, respectively. We further show that ME system performs well for all pH conditions, treatment of real wastewaters as well as wastewaters containing other metals ions (Cr and Zn) along with Cu/Ni. The separation efficiency of Cu and Ni is dependent on applied electrode potential as well as nature and concentration of binding ligand present with comparatively lower separation efficiency achieved in the presence of weaker binding capacity and/or at lower ligand concentration and lower applied electrode potential. As such, some optimization of electrode potential is required depending on the nature/concentration of ligands in the wastewaters. Overall, this study provides new insights into the design and operation of EAOP technology for effective organic abatement and metal recovery from wastewaters containing mixtures of various metal-organic complexes.

Preparation and Characterization of E-PANI-HCL and E-PANI-p-toluensulfonic Acid Indicator Electrodes, SEM-EDX XRD and FTIR Analysis

This research aims to create and characterize the E-PANI indicator electrode membrane using SEM-EDX, XRD and FTIR analysis. PANI conductive polymer is better than PPy conductive polymer, o-NPOE variations are 61% and 66% more flexible in PVC-KTpClPB, as well as variations of one/three drops of 0.5 mL U4002 enzyme in PVA, glutaraldehyde (GA 2.9%). The working method of the potentiometric biosensor used is immobilization of the U4002 enzyme so that the analyte is urea. The multi membrane indicator electrode is E-PANI compared to E-PPy. The membrane consists of four layers, each coated only once on each indicator electrode. The E-PANI membrane analyzed by XRD produces a spectrum pattern with an intensity of 4400.0 (a.u) around 28.64 degrees, similarly E-PPy produces a spectrum pattern with an intensity of 224 (a.u) around 44.54 degrees. FTIR analysis shows an increase in % Transmittance by the indicator electrode using the PANI-HCl conducting polymer instead of PPy-H2SO4. Based on SEM-EDX, XRD and FTIR analysis, the best conductive polymer is PANI-HCl-6 M compared to PPy-H2SO4-8 M

Optical biosensor manufacturing for Chronic Lymphocytic Leukemia biomarker detection with -walled carbon nano tubes-based multi electrodes

All around world, cancer is a major factor in mortality and reduced life expectancy. Even while several treatments are being developed to reduce mortality, chronic pain, and to improve quality of life, these cancer medications still depend in some areas. Monitoring the electrostatic interactions based Fermi level fluctuation caused by biological and chemical species adsorption here on semiconductor surface allows for the early detection of Chronic Lymphocytic Leukemia (CLL). The detection of Chronic Lymphocytic Leukemia (CLL) biomarkers is critical for early diagnosis and prognosis of blood cancer patients. Despite the development of various treatments to minimize fatalities and chronic pain, there is still a gap in the adequacy of these cancer medicines. The proposed technique in this paper shows a novel approach to understanding the operation of an optical biosensor by presenting an in-depth investigation of the sensing mechanism. The developed biosensor sensitivity limit of detection (LOD) was determined, and the employment of a laser (635nm wavelength) to produce photocurrent and photoconductive response was assessed by monitoring Fermi level fluctuations, making this biosensor unique. This suggested method presents a thorough analysis of the sensing mechanism and illustrates a novel approach to knowing the operation of a biosensor. By altering its silane binding time, antibody concentration, and antibody binding duration on that surface of MWCNTs, the sensor's performance may be increased. In this study, multi-wall carbon nano tubes are used to create an optical biosensor for the detection of chronic lymphocytic leukaemia (CLL) (MWCNTs). In this study, bio-electrode characteristics were enhanced to produce a functional biosensor. In this study, complementary investigations like Raman, FTIR, and FESEM evaluations were performed. The sensing procedure has been described in terms of the Fermi level fluctuation produced by the charge transfer.

Experimental Study on Effect of Process Characteristics during Electronic Discharge Machining of Titanium Alloy Using Multi Hole Tool Electrode

Due to outstanding material qualities such as higher strength to weight ratio, resistance to corrosion and resistance to fatigue, titanium alloys (Ti-6Al-4V) are widely applied in aerospace industries. Such a challenging to machine and necessary expensive convenctional machinery materials can cut using Electrical Discharge Machining (EDM). This work involves the study of influence of process characteristics on the performance quality of EDM during machining of Ti-6Al-4V. The process characteristics that are considered in this study are Current (9-15amps) or Input power (I.P. of 3-5 kVA), pulse on (60-80 μsec) and pulse off (20-40μsec) times, the pressure of dielectric fluid (6-10 MPa). The effectiveness of the EDM is measured using rate of tool wear (TWR) and rate of material removal (MRR) during machining, taper angle and surface roughness (SR). Dry brass multi hole tool electrode is used along with deionized water as the dielectric medium. Taguchi L18 orthogonal design is used for experimentation. The optimal combination of process characteristics is determined.

C46 ELECTROPHYSIOLOGICAL ASSESSMENT OF ATRIAL TACHYCARDIA SUBSTRATES IN PATIENTS WITH REPAIRED TETRALOGY OF FALLOT

Abstract Introduction Adults with repaired tetralogy of Fallot (rToF) experience episodes of atrial tachycardia (AT) and radiofrequency catheter ablation (RFCA) is often required but systematic evaluation of the mechanisms and recurrences is lacking. Methods Between January 2013 and October 2021, 20 rToF patients with AT referred for catheter ablation were enrolled. Electrophysiologic study with 3D electroanatomic mapping with multi–electrode mapping catheters was done, with right atrial bipolar voltage and activation mapping of the AT. Three mechanisms were searched: intra–atrial re–entrant tachycardias (IART), focal (FAT), other. Critical isthmus (CI) for IART was identified with activation mapping. FATs were localized according to the earliest uni/bipolar signal. All induced AT were treated. RFCA was aimed at the earliest activation point for FAT and at the critical isthmus for IART, anchoring lesion to fixed obstacles (valve annuli or scar). Written informed consent was provided. Results Among 20 adult (age 46±14 years) and mainly females (n=11, 55%) enrolled pts, 36 AT were documented: 25 (70%) IART, 10 (27%) FAT and only 1 (3%) had a typical atrioventricular nodal reentrant tachycardia. Mean tachycardia cycle length was 307±95 ms. Two ATs were induced in 11 pts, 3 in 4 pts and 4 in 2 during index EPS. Among IART, cavo–tricuspid isthmus (CTI) was the prevalent CI (n=14, 60%), while incisional IART (IARTinc, atriotomy and superior and inferior vena cava orifices, SVC and IVC, respectively) was the second mechanism (n=9, 39%). In two pts, due to non–inducibility, a pre–emptive lesion set comprising in one case CTI and in the second case CTI+SVC–atriotomy–IVC line was performed. Among FAT, in 3 cases the AT was mapped in the coronary sinus, in two at the tricuspid annulus, other at the crista terminalis, right appendage base, posterolateral scar or between atriotomy and SVC. During a median follow–up of 23 months (interquartile range, 6–37) recurrence occurred in 8 pts (25% of pts, 22% of tachycardias). Pts with recurrences were younger (43±7 vs. 48±17 y, p=0.04); no differences were found according to critical isthmus location (4 CTI and 4 IARTinc, 50%, p=ns). Conclusions Among rToF pts with AT, IART is the prevalent mechanism and CTI is the prevalent CI; atriotomy scar, however, is involved in a substantial portion of the critical isthmuses of the IART; FAT location is much more variable. Long–term freedom from AT in this clinical setting is encouraging.

Identifying the engagement of a brain network during a targeted tDCS-fMRI experiment using a machine learning approach.

Transcranial direct current stimulation (tDCS) can noninvasively modulate behavior, cognition, and physiologic brain functions depending on polarity and dose of stimulation as well as montage of electrodes. Concurrent tDCS-fMRI presents a novel way to explore the parameter space of non-invasive brain stimulation and to inform the experimenter as well as the participant if a targeted brain region or a network of spatially separate brain regions has been engaged and modulated. We compared a multi-electrode (ME) with a single electrode (SE) montage and both active conditions with a no-stimulation (NS) control condition to assess the engagement of a brain network and the ability of different electrode montages to modulate network activity. The multi-electrode montage targeted nodal regions of the right Arcuate Fasciculus Network (AFN) with anodal electrodes placed over the skull position of the posterior superior temporal/middle temporal gyrus (STG/MTG), supramarginal gyrus (SMG), posterior inferior frontal gyrus (IFG) and a return cathodal electrode over the left supraorbital region. In comparison, the single electrode montage used only one anodal electrode over a nodal brain region of the AFN, but varied the location between STG/MTG, SMG, and posterior IFG for different participants. Whole-brain rs-fMRI was obtained approximately every three seconds. The tDCS-stimulator was turned on at 3 minutes after the scanning started. A 4D rs-fMRI data set was converted to dynamic functional connectivity (DFC) matrices using a set of ROI pairs belonging to the AFN as well as other unrelated brain networks. In this study, we evaluated the performance of five algorithms to classify the DFC matrices from the three conditions (ME, SE, NS) into three different categories. The highest accuracy of 0.92 was obtained for the classification of the ME condition using the K Nearest Neighbor (KNN) algorithm. In other words, applying the classification algorithm allowed us to identify the engagement of the AFN and the ME condition was the best montage to achieve such an engagement. The top 5 ROI pairs that made a major contribution to the classification of participant's rs-fMRI data were identified using model performance parameters; ROI pairs were mainly located within the right AFN. This proof-of-concept study using a classification algorithm approach can be expanded to create a near real-time feedback system at a participant level to detect the engagement and modulation of a brain network that spans multiple brain lobes.

Tuning the Cation/Anion Adsorption Balance with a Multi-Electrode Capacitive-Deionization Process

Capacitive deionization (CDI) is an emerging technique for purifying water by removing ions. Recent experimental studies have reported that the anion/cation adsorption can be naturally imbalanced, even for a solution with just sodium and chloride, and suggested a link between imbalance and Faradaic leakages. However, these effects have been missing from conventional models. In this work, we developed a new circuit model to better understand the connection between Faradaic leakages and adsorption imbalance. The theory demonstrates that the effect emerges in a model that includes leakages, considers leakages on both electrodes separately, and considers different leakage resistance on the two electrodes. Having the model, it is possible to analyze and quantify the influence of the leakage resistance and other material properties on the adsorption imbalance. Leveraging these results, we further present a multi-electrode (ME) device design. The setup adds a third electrode to the spacer channel and can tune or eliminate the adsorption imbalance based on appropriately distributing the voltage across the electrodes. In conclusion, we describe a charge leakage mechanism responsible for the imbalance of ion adsorption and a flexible device design to tune the anion/cation removal.

Spontaneous Epileptic Recordings from hiPSC-Derived Cortical Neurons Cultured with a Human Epileptic Brain Biopsy on a Multi Electrode Array

A growing societal awareness is calling upon scientists to reconsider the use of animals in research, which stimulates the development of translational in vitro models. The physiological and architectural interactions between different cell types within an organ present a challenge to these models, particularly for a complex organ such as the brain. Thus far, in vitro brain models mostly consist of a single cell type and demonstrate little predictive value. Here, we present a co-culture of an epileptic human neocortical biopsy on a layer of human induced pluripotent stem cell (hiPSC)-derived cortical neurons. The activity of the cortical neurons was recorded by a 120-electrode multi-electrode array. Recordings were obtained at 0, 3, and 6 days after assembly and compared to those obtained from cortical neurons without a biopsy. On all three recording days, the hybrid model displayed a firing rate, burst behavior, number of isolated spikes, inter-spike interval, and network bursting pattern that aligns with the characteristics of an epileptic network as reported by others. Thus, this novel model may be a non-animal, translational alternative for testing new therapies up to six days after resection.

Atrial tattoos lines: a new method to terminate atrial fibrillation

Abstract Introduction Atrial fibrillation (AF) is the most common cardiac arrhythmia affecting more than 4% of the world's population. Furthermore, the vulnerable substrate underlying atrial cardiomyopathy remains far from being understood. Atrial cardiomyopathy is a highly complex and heterogeneous disease that occurs in the context of various clinical backgrounds, which explains the heterogenous success of established atrial ablation strategies such as pulmonary vein isolation. Here we developed a new interventional method for the treatment of AF using a tattooing procedure of silver nanowires in the atria to create circular lines of increased conductivity to prevent irregular electrical propagation. Purpose In a translational study, we tested a newly developed interventional method to terminate AF by injecting lines of silver nanowires to increase tissue conductivity. Methods The developed tattoo method was tested in vivo using an established large animal AF model of the domestic pig. Pigs (n=10) with atrial fibrillation were either treated with right atrial tattoo lines using a transmural injection procedure of silver nanowires as closed lines in the atrium or got a sham treatment with saline injections. Over 21 days, AF was induced and monitored (AF burden) by an intracardiac dual-chamber device with a biofeedback induction algorithm. Initially and before final termination, conventional electrophysiological investigation and atrial 3D mapping, echocardiography and epicardial multi electrode array (MEA) measurements were performed. Following the 21 days observation period, the heart was extracted and freshly isolated atrial cardiomyocytes were subjected to cellular electrophysiological, molecular and histochemical characterization. Electrophysiological data was used for in silico modelling of arrhythmia termination and wave propagation. The study protocol was approved by the animal ethics committee. Results The AF burden was significantly reduced (AF burden <10%) in the group treated with the new atrial tattoo line method compared to sham treated pigs. The bi-atrial diameters, quantified by echocardiography, were significantly smaller in the treatment group. Atrial refractory period was significantly shorter in the sham treated pigs. A significant increase of connexin 43 was observed in the injection area of silver nanowires in the myocardium. Measurements with MEA demonstrated increased conduction velocity by a factor of 1.5–2.0 in the areas of silver nanowire injections. Additionally, in silico modelling showed the termination of AF via the created conduction lines. Conclusion The newly developed interventional method of the creation of atrial lines with increased tissue conductivity using silver nanowires could successfully terminate AF in pigs. Perspectively, this new myocardial tattooing technique may be a promising treatment strategy for patients with complex atrial cardiomyopathies to terminate atrial arrhythmias. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Else Kröner Fresenius Foundation

Endo- and epicardial mapping of spontaneous ventricular fibrillation during acute myocardial infarction in a porcine model

Abstract Introduction Ventricular fibrillation (VF) during the first minutes of acute myocardial infarction (AMI) is among the most frequent causes of sudden cardiac death. Albeit mechanisms for arrhythmogenesis during ischemia are well understood on a cellular level, little is known in an in-vivo setting. Aim Aim of this study was the development and characterization of a porcine model of AMI and spontaneous VF with continuous electrical mapping using a non-contact mapping system (EnSite Array) in the left ventricle (LV) and an electrode sock covering the whole heart. Activation-recovery intervals (ARI), beat-to-beat variation in repolarization (BVR), and ectopic activation were measured. Methods Nineteen Danish Landrace pigs (56±4 kg, heart weight 251±20 g) were anaesthetized, equipped with electrophysiological (EP) catheters in the coronary sinus, right and LV as well as a multi electrode array (St. Jude, EnSite Array) catheter in the LV. Thoracotomy was performed and the sock electrode was placed on the pericardium covering the anterior and the posterior surface of the heart. Finally, the mid-left anterior descendent artery was occluded with a percutaneous transluminal coronary angioplasty balloon to induce AMI and kept in place for 45 minutes followed by 20 minutes of reperfusion. Data from both systems were analyzed offline using a custom-made software. Results All pigs had stable hemodynamic parameters during the procedure. Spontaneous VF occurred in 8/19 pigs during the occlusion period. Epi- and endocardial mapping showed similar shortening of ARI in the infarcted area (Figure 1A). AMI shortened ARI in the ischemic area to a greater extend in pigs that developed VF (Figure 1B) and caused beat-to-beat variation in repolarization (BVR) in later phases (Figure 1C). Ectopic beats proceeding spontaneous VF varied in activation site and subsequent repolarization (Figure 1D, left). Multiple short-coupled ectopic beats destabilized the electrical substrate further and led to progressive ARI shortening (Figure 1D, last 4 beats). Conclusion We present the first whole heart mapping experiments of spontaneous VF during AMI with endo- and epicardial mapping. Pigs with VF had shorter ARI, greater dispersion but similar BVR during AMI compared to those without VF. These findings provide a deeper understanding of arrhythmogenesis during AMI and can help to develop new antiarrhythmic drugs or to assess risk factors of VF. Funding Acknowledgement Type of funding sources: None.

Abstract P1035: Co-culturing Human Induced Pluripotent Stem Cell-derived Cardiomyocytes With Mesenchymal Stem Cells Promotes Their Maturation And Enhances Cardioprotection Under Hypoxic Stress

Introduction: Co-culturing human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiCMs) with other stem/progenitor cells like bone-marrow mesenchymal stem cells (BM-MSCs) and endothelial progenitors has been shown to improve their survival post transplantation into ischemic hearts. Co-culturing with other cardiac cells has also shown to improve the maturation of hiCMs in vitro. However, the potential of co-culturing hiPSC-derived MSCs (hiMSCs) for hiCM maturation and cardioprotection has not been explored. Hypothesis: We hypothesize that co-culturing of hiMSCs with hiCMs significantly alters the cells’ proteome, improves hiCM maturation, and enhances cardioprotection. Results: hiCMs were co-cultured with hiMSCs for one week at a ratio of 3:1. To evaluate the effect of hiMSCs on hiCM maturation in the co-culture, changes in the hiCM function and gene expression were assessed via multi electrode array (MEA) analysis and qPCR, respectively. MEA analysis showed an increase in ADP50 and ADP90 in addition to improved response to cardiac drugs in hiCMs co-cultured with hiMSCs as compared to hiCM-only cultures, indicating improved maturation of hiCMs in the co-culture. Furthermore, gene expression analysis showed an increased expression of mature CM-associated genes (MYH7, TNNT2). When subjected to hypoxic stress (1% O 2 ), we also observed a significant decrease in the number of TUNEL positive cells in the co-cultures as compared to hiCM-only culture. Assessment of hiCM functionality via MEA analysis showed an improved cardioprotection in co-cultures as compared to the single cell-type cultures. Furthermore, proteomic analysis demonstrated increased expression of cardioprotective growth factors (GFs): HGF, VEGFA and IGFBP-1 in the conditioned medium of the co-cultured cells versus single cell-type cultures. Conclusion: Overall, our results established that co-culturing hiCMs with hiMSCs improved cardioprotection via increased the expression of cardioprotective growth factors and enhanced the maturation of hiCMs in vitro.

Combined masked LCD-printing and microfabrication for bioimpedance-chips

Biomedical in vitro sensors use cell cultures grown on sensor chips for drug testing, toxicological screening, studying pathologic processes in tissue and for personalized medicine. Microfluidic systems and chips bridge the gap of the biological micro world to our accessible macro world, creating the interface between e.g., cells on a chip to reservoirs and pumps. Prototype and low volume lab scale microfluidic devices have traditionally been realized by soft lithography using polydimethylsiloxane (PDMS) technology. Recently, rapid prototyping of microfluidic devices using direct 3D printing has become widely available. Usually, the 3D printed parts are (i) either stand-alone systems requiring only fluidic connections, or (ii) they need to be carefully aligned and skilfully attached to the rigid micro fabricated chip. This post-fabrication attachment is time-consuming and a frequent source of error. In this work the fabrication of the microchip and the microfluidic system have been integrated into a multi technology fabrication process. For the first time we demonstrate the “on-chip 3D printing” of a microfluidic attachment directly onto an in-house fabricated multi electrode array chip. The process uses a desktop-sized LCD resin printer and eliminates the time-consuming post-deposition alignment and attachment. Biocompatibility of the used resin was confirmed for murine fibroblasts and validates this multi technology approach for biomedical cell chips. • Direct 3D printing of microfluidic structures on microchip demonstrated. • Electrophysiology measuring device fabricated by direct 3D printing. • No post-printing attachment and positioning step required. • Biocompatibility of used resin evaluated positively for short time culture.