Intracellular Action Potential Recordings Research Articles

Sensitive Intracellular Recording of Action Potentials by Supramolecular Self‐Assembled Electrodes

AbstractDeveloping accurate electrophysiological recording platforms is crucial for investigating cellular electrical activities, understanding the mechanisms underlying cardiovascular disease, and advancing therapeutic strategies. While the successful recording of intracellular electrophysiological status has been achieved by 3D micro/nano devices, their preparation through demanding micro/nanofabrication and poorly controllable solvothermal synthesis is an impediment to widespread utilization. Easier‐to‐access recording electrodes are needed. To address this challenge, a simple and efficient supramolecular self‐assembly strategy that allows access to novel 3D electrodes is introduced. It relies on small organic molecules that can be self‐assembled efficiently into various 3D nanostructures, including lamellated nanosheets, thin nanobelts, and short rod‐like structures. Electrodes prepared through the present self‐assembly process are considerably simpler and more cost‐effective than conventional 3D micro/nanoelectrodes prepared through fabrication or solvothermal synthesis. It is demonstrated that the present electrodes allow for higher quality and prolonged intracellular recordings of action potentials as compared to similarly sized conventional planar electrodes. The noted improvements are attributed to the fact that 3D geometrical electrodes enhance the cell‐electrode interface, ensuring tight coupling and effective electroporation. This work showcases how supramolecular self‐assembly might emerge as a promising and powerful electrode preparation strategy that may facilitate low‐cost electrophysiological studies.

A jump in the atrioventricular conduction curve is not caused by a switch from fast pathway to slow pathway conduction.

Background: A jump in the atrioventricular (AV) conduction curve is the current clinical criterion of dual-pathway electrophysiology. However, the assumption that a jump indicates a switch from fast pathway (FP) to slow pathway (SP) conduction remains unconfirmed. This study was carried out to investigate whether a jump indeed indicates a transition from FP to SP conduction, and if not, what the potential cause is. Methods: Eighty-one experimental records from rabbit AV nodal preparations containing the following data were analyzed: 1) had at least one AV conduction curve and 2) had recording of His electrogram alternans (a validated new index of dual-pathway conduction). Most cases also had intracellular action potential recordings from the AV nodal fibers. Results: Of the 81 preparations, 11 (13%) showed a jump in the AV conduction curve. The jumps always occurred after the FP to SP transition. The FP-SP transition occurred at prematurity at 196 ± 39ms versus the jump at 114 ± 13ms (p < 0.001). The beat with a jump showed an SP-FP pattern in seven and an SP-SP pattern in four preparations. The jumps were always associated with and most likely caused by the formation of intranodal/nodal-atrial reentry and its subsequent conduction, rather than a switch from FP to SP conduction. Conclusion: Contrary to what has been assumed, a transition from FP to SP conduction does not produce a jump in the AV conduction curve. A jump in the AV conduction curve is most likely caused by the formation of intranodal/nodal-atrial reentry and its subsequent conduction.

Elevating intracellular action potential recording in cardiomyocytes: A precision-enhanced and biosafe single-pulse electroporation system

Action potentials play a pivotal role in diverse cardiovascular physiological mechanisms. A comprehensive understanding of these intricate mechanisms necessitates a high-fidelity intracellular electrophysiological investigative approach. The amalgamation of micro-/nano-electrode arrays and electroporation confers substantial advantages in terms of high-resolution intracellular recording capabilities. Nonetheless, electroporation systems typically lack precise control, and commonly employed electroporation modes, involving tailored sequences, may escalate cellular damage and perturbation of normal physiological functions due to the multiple or higher-intensity electrical pulses. In this study, we developed an innovative electrophysiological biosensing system customized to facilitate precise single-pulse electroporation. This advancement serves to achieve optimal and uninterrupted intracellular action potential recording within cardiomyocytes. The refinement of the single-pulse electroporation technique is realized through the integration of the electroporation and assessment biosensing system, thereby ensuring a consistent and reliable means of achieving stable intracellular access. Our investigation has unveiled that the optimized single-pulse electroporation technique not only maintains robust biosafety standards but also enables the continuous capture of intracellular electrophysiological signals across an expansive three-day period. The universality of this biosensing system, adaptable to various micro/nano devices, furnishes real-time analysis and feedback concerning electroporation efficacy, guaranteeing the sustained, secure, and high-fidelity acquisition of intracellular data, thereby propelling the field of cardiovascular electrophysiological research.

Abstract 12422: Does a Jump in the Atrioventricular Conduction Curve Really Indicate a Switch From Fast Pathway to Slow Pathway Conduction?

Introduction: A jump in the atrioventricular (AV) conduction curve (aka, a discontinuous curve) remains the current clinical criterion for diagnosing dual pathway AV nodal electrophysiology. However, it has never been proven that a jump in the AV conduction curve indicating a transition from fast pathway (FP) to slow pathway (SP) conduction, as it has been assumed. Hypothesis: A jump in the AV conduction curve may not reflect the transition from FP to SP conduction, as assumed it does by the current clinical criterion. Methods: Eighty-one experimental records from rabbit AV nodal preparations containing the following data were analyzed. 1. had at least one AV conduction curve, and 2. had intracellular action potential recordings from AV nodal fibers and/or recording of His electrogram alternans (a validated new index of dual pathway conduction). Results: There were 11 (13%) of 81 preparations showing a jump in the AV conduction curve. In these preparations, the transition from FP to SP conduction was smooth. The jumps always occurred after the FP to SP transition at a much shorter prematurity (Figure). On average, the FP-SP transition occurred at prematurity of 196±39ms versus the jump at 117±9ms (P&lt;0.001). Complex intranodal/nodal-atrial reentries were detected after the FP to SP transition. The jumps were always associated with and most likely caused by the intranodal/nodal-atrial reentry and its subsequent conduction to the His bundle, rather than a direct conduction by the premature beat itself. Conclusions: The transition from FP to SP conduction does not produce a jump in the AV conduction curve. A jump in the AV conduction curve is likely caused by induction of intranodal/nodal-atrial reentry by the premature beat and the subsequent conduction of the reentrant beat to the His bundle, rather than a direct conduction by the premature beat itself. Thus, a jump in the AV conduction curve as the current clinical criterion of dual pathway conduction should be invalidated.

Sensitive and prolonged intracellular electrophysiological recording by three‐dimensional nanodensity regulation

AbstractWith the advancement of micro/nanotechnologies, multielectrodes arrays (MEAs) with different three‐dimensional (3D) micro/nanostructures have been developed to achieve intracellular action potential recording of cardiomyocytes. However, the effect of the 3D micro/nanostructures density on the intracellular recording has not been fully investigated. In this work, 3D tunable nanodensity electrode arrays (TNDEA) are fabricated by hydrothermal synthesis and standard microfabrication to explore the effect of nanodensity regulation on intracellular biosensing. By low‐voltage electroporation, the signal quality of intracellular potentials recorded by the low‐nanodensity TNDEA showed was significantly improved compared to those recorded by the high‐nanodensity TNDEA. The low‐nanodensity TNDEA improved the amplitude (up to 7.7 mV), signal‐to‐noise ratio (SNR) (up to 69.46 dB), recording duration (up to 83 min), and recording yield (∼100%). The 3D nanodensity regulating strategy has achieved sensitive and prolonged intracellular biosensing of action potentials and is expected to be a powerful electrophysiological research tool in the biomedical field.

Direct recording of action potentials of cardiomyocytes through solution processed planar electrolyte-gated field-effect transistors

To achieve intracellular recording of action potentials by using simple devices that can be easily fabricated and processed is crucial in cardiology and neuroscience. Present tools and technology include invasive patch clamp technique, 3D nanostructures often combined with electro/opto poration methods and nanodevices such as nanowire field-effect transistors. However, these approaches mostly require complex manufacturing processes or are invasive. In this work, we report the spontaneous intracellular-like recording of cardiac cells using a cost-effective, planar Electrolyte-Gated Field-Effect Transistor (EGFET) based on solution-processed polymer-wrapped monochiral semiconducting single-walled carbon nanotubes (SWCNTs). By simply turning on the transistor, spontaneous recordings of intracellular-like action potentials of human induced pluripotent stem cells derived cardiomyocytes are enabled. In addition, we demonstrate that the same planar EGFET can also be employed as a platform for electroporation with significant device performance and cell viability. The simplicity of the device combined with the high signal to noise ratio opens up new opportunities for low-cost, reliable, and flexible biosensors and arrays for high quality parallel recording of cellular action potentials.

PO-01-146 PRO-ARRHYTHMIC REMODELLING OF THE PULMONARY VEIN AND LEFT ATRIAL APPENDAGE JUNCTION IN AN ANIMAL MODEL OF ENDURANCE EXERCISE

An increased incidence of atrial fibrillation (AF) is observed in endurance athletes but the mechanism underlying this is not fully known. Electrophysiological remodelling of pulmonary vein sleeve myocytes (PV), and the PV to left atrial junction may contribute to arrhythmogenesis. PV-left atrial appendage (LAA) preparations were isolated from male C57BL/6J mice after 6 weeks of treadmill exercise (ExT, running for 2 hours per day at 60-80% maximal oxygen uptake) and compared to age-matched sedentary mice (Sed). Intracellular action potential recordings and high density multielectrode array mapping was performed. Sections were stained for Masson’s trichrome to assess fibrosis. Data are expressed as mean ± standard error. In both groups there was spontaneous activity with burst firing in the PV, that significantly increased on superfusion with 10 micromolar noradrenaline (NA). There was more frequent burst activity in ExT PV (n=8/10; inter-burst time Sed 14.7 ± 8.4 s vs. ExT 4.9 ± 1.2 s; p<0.01) and programmed electrical stimulation from the right superior PV (rsPV) ostium at 20 Hz induced PV firing bursts with a shorter cycle length in ExT (n=5/5, Sed 313 ± 53 ms vs. ExT 223 ± 37 ms, p=0.05). NA induced a shift in the site of earliest activation from rsPV towards PV-LAA junction in 50% of ExT preparations vs. 25% in Sed (n=8/9). Conduction velocity (CV) at the PV-LAA junction was slowed by 65% in ExT (n=8/9, Sed 1.10 ± 0.26 m/s vs. ExT 0.39 ± 0.08 m/s, p<0.05) and CV from the site of earliest activation toward LAA within the PV was slowed (Sed 0.46 ± 0.10 m/s vs. ExT 0.20 ± 0.03 m/s, p<0.05) in ExT. Increased collagen deposition was seen the ExT PV-LAA junction vs. Sed (n =3/5; Sed 23 ± 4% vs. ExT 37 ± 1%, p<0.01). Exercise training caused alterations to the PV electrical susbtrate with an observed increase in burst frequency and reduction in cycle length in trained mice. There was also conduction slowing in the PVs and PV-LA junction of trained animals with evidence of increased collagen deposition. These data provide new insight into the electroanatomical substrate that predisposes athletes to AF.

Integrated Cardiomyocyte-Based Biosensing Platform for Electroporation-Triggered Intracellular Recording in Parallel with Delivery Efficiency Evaluation.

Electroporation is a proven technique that can record action potential of cardiomyocytes and serve for biomolecular delivery. To ensure high cell viability, micro-nanodevices cooperating with low-voltage electroporation are frequently utilized in research, and the effectiveness of delivery for intracellular access is typically assessed using an optical imaging approach like flow cytometry. However, the efficiency of in situ biomedical studies is hampered by the intricacy of these analytical approaches. Here, we develop an integrated cardiomyocyte-based biosensing platform to effectively record action potential and evaluate the electroporation quality in terms of viability, delivery efficiency, and mortality. The ITO-MEA device of the platform possesses sensing/stimulating electrodes which combines with the self-developed system to achieve intracellular action potential recording and delivery by electroporation trigger. Moreover, the image acquisition processing system analyzes various parameters effectively to assess delivery performance. Therefore, this platform has the potential for drug delivery therapy and pathology research for cardiology.

Scalable and Robust Hollow Nanopillar Electrode for Enhanced Intracellular Action Potential Recording.

Electrophysiology is a unique biomarker of the electrogenic cells that can perform a disease investigation or drug assessment. In the recent decade, vertical nanoelectrode arrays can successfully achieve a high-quality intracellular electrophysiological study in electrogenic cells and their networks. However, a high success rate and high-quality and long-term intracellular recording using low-cost nanostructures is still a considerable challenge. Herein, we develop a scalable and robust hollow nanopillar electrode to achieve enhanced intracellular recording of cardiomyocytes. The template-based synthesis of vertical hollow nanopillars is compatible with large-scale and efficient microfabrication processes and is convenient to regulate the geometry of hollow nanopillars. Compared with the conventional same-size planar electrode, the regulating height of a hollow nanopillar can achieve high-quality and prolonged intracellular recordings, which can improve the cell-electrode interface for tight coupling and effective electroporation. It is demonstrated that the geometry regulation of a nanostructure is a powerful strategy to enhance intracellular recording.

Porous Polyethylene Terephthalate Nanotemplate Electrodes for Sensitive Intracellular Recording of Action Potentials.

New strategies for intracellular electrophysiology break the spatiotemporal limitation of the action potential and lead a notable advance in the investigation of electrically excitable cells and their network. Although successful applications of intracellular recording have been achieved by 3D micro/nanodevices, complex micro/nanofabrication processes preclude the progress of extensive applications. We address this challenge by introducing porous polyethylene terephthalate (PET) membrane to develop a new type of nanotemplate electrode. This nanotemplate electrode is manufactured following a fabrication process on a porous PET membrane by atomic layer deposition. The 3D nanotemplate electrodes afford intracellular access to cardiomyocytes to report intracellular-like action potentials. These controllable nanotemplate electrodes exhibit sensitive and prolonged intracellular recordings of action potentials compared with free-growing 3D nanoelectrodes. This study indicates that the optimized structure of the nanoelectrode significantly promotes the performance of intracellular recording to assess electrophysiology in the fields of cardiology and neuroscience at an action potential level.

A universal, multimodal cell-based biosensing platform for optimal intracellular action potential recording

Intracellular recording of action potentials is an essential mean for studying disease mechanisms, and for electrophysiological studies, particularly in excitable cells as cardiomyocytes or neurons. Current strategies to obtain intracellular recordings include three-dimensional (3D) nanoelectrodes that can effectively penetrate the cell membrane and achieve high-quality intracellular recordings in a minimally invasive manner, or transient electroporation of the membrane that can yield temporary intracellular access. However, the former strategy requires a complicated and costly fabrication process, and the latter strategy suffers from high dependency on the method of application of electroporation, yielding inconsistent, suboptimal recordings. These factors hinder the high throughput use of these strategies in electrophysiological studies. In this work, we propose an advanced cell-based biosensing platform that relies on electroporation to produce consistent, high-quality intracellular recordings. The suggested universal system can be integrated with any electrode array, and it enables tunable electroporation with controllable pulse parameters, while the recorded potentials can be analyzed in real time to provide instantaneous feedback on the electroporation effectiveness. This integrated system enables the user to perform electroporation, record and assess the obtained signals in a facile manner, to ultimately achieve stable, reliable, intracellular recording. Moreover, the proposed platform relies on microelectrode arrays which are suited for large-scale production, and additional modules that are low-cost. Using this platform, we demonstrate the tuning of electroporation pulse width, pulse number, and amplitude, to achieve effective electroporation and high-quality intracellular recordings. This integrated platform has the potential to enable larger scale, repeatable, convenient, and low-cost electrophysiological studies.

An organic transistor matrix for multipoint intracellular action potential recording

Electrode arrays are widely used for multipoint recording of electrophysiological activities, and organic electronics have been utilized to achieve both high performance and biocompatibility. However, extracellular electrode arrays record the field potential instead of the membrane potential itself, resulting in the loss of information and signal amplitude. Although much effort has been dedicated to developing intracellular access methods, their three-dimensional structures and advanced protocols prohibited implementation with organic electronics. Here, we show an organic electrochemical transistor (OECT) matrix for the intracellular action potential recording. The driving voltage of sensor matrix simultaneously causes electroporation so that intracellular action potentials are recorded with simple equipment. The amplitude of the recorded peaks was larger than that of an extracellular field potential recording, and it was further enhanced by tuning the driving voltage and geometry of OECTs. The capability of miniaturization and multiplexed recording was demonstrated through a 4 × 4 action potential mapping using a matrix of 5- × 5-μm2 OECTs. Those features are realized using a mild fabrication process and a simple circuit without limiting the potential applications of functional organic electronics.

Intracellular action potential recordings from cardiomyocytes by ultrafast pulsed laser irradiation of fuzzy graphene microelectrodes.

Graphene with its unique electrical properties is a promising candidate for carbon-based biosensors such as microelectrodes and field effect transistors. Recently, graphene biosensors were successfully used for extracellular recording of action potentials in electrogenic cells; however, intracellular recordings remain beyond their current capabilities because of the lack of an efficient cell poration method. Here, we present a microelectrode platform consisting of out-of-plane grown three-dimensional fuzzy graphene (3DFG) that enables recording of intracellular cardiac action potentials with high signal-to-noise ratio. We exploit the generation of hot carriers by ultrafast pulsed laser for porating the cell membrane and creating an intimate contact between the 3DFG electrodes and the intracellular domain. This approach enables us to detect the effects of drugs on the action potential shape of human-derived cardiomyocytes. The 3DFG electrodes combined with laser poration may be used for all-carbon intracellular microelectrode arrays to allow monitoring of the cellular electrophysiological state.

Cutaneous Aβ-Non-nociceptive, but Not C-Nociceptive, Dorsal Root Ganglion Neurons Exhibit Spontaneous Activity in the Streptozotocin Rat Model of Painful Diabetic Neuropathy in vivo.

Diabetic peripheral neuropathic pain (DPNP) is the most devastating complication of diabetes mellitus. Unfortunately, successful therapy for DPNP remains a challenge because its pathogenesis is still elusive. However, DPNP is believed to be due partly to abnormal hyperexcitability of dorsal root ganglion (DRG) neurons, but the relative contributions of specific functional subtypes remain largely unknown. Here, using the strepotozotocin (STZ) rat model of DPNP induced by a STZ injection (60 mg/kg, i.p), and intracellular recordings of action potentials (APs) from DRG neurons in anesthetized rats, we examined electrophysiological changes in C-and Aβ-nociceptive and Aβ-low threshold mechanoreceptive (LTM) neurons that may contribute to DPNP. Compared with control, we found in STZ-rats with established pain hypersensitivity (5 weeks post-STZ) several significant changes including: (a) A 23% increase in the incidence of spontaneous activity (SA) in Aβ-LTMs (but not C-mechanosensitive nociceptors) that may cause dysesthesias/paresthesia suffered by DPNP patients, (b) membrane hyperpolarization and a ∼85% reduction in SA rate in Aβ-LTMs by Kv7 channel activation with retigabine (6 mg/kg, i.v.) suggesting that Kv7/M channels may be involved in mechanisms of SA generation in Aβ-LTMs, (c) decreases in AP duration and in duration and amplitude of afterhyperpolarization (AHP) in C-and/or Aβ-nociceptors. These faster AP and AHP kinetics may lead to repetitive firing and an increase in afferent input to the CNS and thereby contribute to DPNP development, and (d) a decrease in the electrical thresholds of Aβ-nociceptors that may contribute to their sensitization, and thus to the resulting hypersensitivity associated with DPNP.

Sinus node-like pacemaker mechanisms regulate ectopic pacemaker activity in the adult rat atrioventricular ring

In adult mammalian hearts, atrioventricular rings (AVRs) surround the atrial orifices of atrioventricular valves and are hotbed of ectopic activity in patients with focal atrial tachycardia. Experimental data offering mechanistic insights into initiation and maintenance of ectopic foci is lacking. We aimed to characterise AVRs in structurally normal rat hearts, identify arrhythmia predisposition and investigate mechanisms underlying arrhythmogenicity. Extracellular potential mapping and intracellular action potential recording techniques were used for electrophysiology, qPCR for gene and, Western blot and immunohistochemistry for protein expression. Conditions favouring ectopic foci were assessed by simulations. In right atrial preparations, sinus node (SN) was dominant and AVRs displayed 1:1 impulse conduction. Detaching SN unmasked ectopic pacemaking in AVRs and pacemaker action potentials were SN-like. Blocking pacemaker current If, and disrupting intracellular Ca2+ release, prolonged spontaneous cycle length in AVRs, indicating a role for SN-like pacemaker mechanisms. AVRs labelled positive for HCN4, and SERCA2a was comparable to SN. Pacemaking was potentiated by isoproterenol and abolished with carbachol and AVRs had abundant sympathetic nerve endings. β2-adrenergic and M2-muscarinic receptor mRNA and β2-receptor protein were comparable to SN. In computer simulations of a sick SN, ectopic foci in AVR were unmasked, causing transient suppression of SN pacemaking.

Plasmonic meta-electrodes allow intracellular recordings at network level on high-density CMOS-multi-electrode arrays.

The ability to monitor electrogenic cells accurately plays a pivotal role in neuroscience, cardiology and cell biology. Despite pioneering research and long-lasting efforts, the existing methods for intracellular recording of action potentials on the large network scale suffer limitations that prevent their widespread use. Here, we introduce the concept of a meta-electrode, a planar porous electrode that mimics the optical and biological behaviour of three-dimensional plasmonic antennas but also preserves the ability to work as an electrode. Its synergistic combination with plasmonic optoacoustic poration allows commercial complementary metal-oxide semiconductor multi-electrode arrays to record intracellular action potentials in large cellular networks. We apply this approach to measure signals from human-induced pluripotent stem cell-derived cardiac cells, rodent primary cardiomyocytes and immortalized cell types and demonstrate the possibility of non-invasively testing a variety of relevant drugs. Due to its robustness and easiness of use, we expect the method will be rapidly adopted by the scientific community and by pharmaceutical companies.

Multi-Modal 16,384-Electrode CMOS MEA with 16 Independent Multi-Well Assays for Physiological Studies of Different Cellular Models

Multi-Modal 16,384-Electrode CMOS MEA with 16 Independent Multi-Well Assays for Physiological Studies of Different Cellular Models

Accurate nanoelectrode recording of human pluripotent stem cell-derived cardiomyocytes for assaying drugs and modeling disease

The measurement of the electrophysiology of human pluripotent stem cell-derived cardiomyocytes is critical for their biomedical applications, from disease modeling to drug screening. Yet, a method that enables the high-throughput intracellular electrophysiology measurement of single cardiomyocytes in adherent culture is not available. To address this area, we have fabricated vertical nanopillar electrodes that can record intracellular action potentials from up to 60 single beating cardiomyocytes. Intracellular access is achieved by highly localized electroporation, which allows for low impedance electrical access to the intracellular voltage. Herein, we demonstrate that this method provides the accurate measurement of the shape and duration of intracellular action potentials, validated by patch clamp, and can facilitate cellular drug screening and disease modeling using human pluripotent stem cells. This study validates the use of nanopillar electrodes for myriad further applications of human pluripotent stem cell-derived cardiomyocytes such as cardiomyocyte maturation monitoring and electrophysiology-contractile force correlation.

A Sexy Approach to Pacemaking

Introduction: The sinoatrial node (SAN) is the primary pacemaker of the heart. Clinical evidence shows that SAN function differs between sexes. Males have slower resting (extrinsic and intrinsic) heart rates, and longer corrected SAN recovery time compared with females. Hypothesis: Sex based differences may be due to SAN ion channel differences. Therefore, we investigated functional behaviour and molecular makeup of SANs in male and female rats. Methods: Intracellular action potential recordings were obtained using sharp microelectrode technique (n=5 each). Gene expression was measured with quantitative PCR (n=6 each). Results: The amplitude of the action potential was significantly higher in male SANs (45.3 ± 2.4) compared with female (31.7 ± 2.5). The upstroke velocity (dV/dtmax) was significantly faster in female SANs (16.4 ± 1.6) compared with male (9.1 ± 1.5). Out of 96 transcripts investigated, two were significantly different between the sexes. L-Type Ca2+ channel, Cav1.3, and acetylcholine activated K+ channel, Kir3.1, mRNA levels were significantly higher in female SANs (66.6% and 45.6% respectively) compared with male. Immunolabelling for Cav1.3 showed levels were significantly higher in female SANs compared with male (18.6%, n=6 each). Inhibition of Cav1.3 with nifedipine (5μM) showed greater effect on the beating rate of male SANs compared with female (43%). A non-coding RNA, miR-139-3p (predicted by Ingenuity IPA software to affect Cav1.3) showed greater effect on the beating rate of male SAN preparations compared with female. Mathematical modelling showed that a higher density of Cav1.3 (as in the case of females) has a protective role from sinoatrial node arrhythmias. Conclusion: This study identified functional and molecular differences in key pacemaker ion channels in SAN between sexes. These differences advance our understanding of gender differences in cardiac electrophysiology and may have implications for gender specific design of anti-arrhythmic drugs and biological pacemakers.

Iridium oxide nanotube electrodes for sensitive and prolonged intracellular measurement of action potentials

Intracellular recording of action potentials is important to understand electrically-excitable cells. Recently, vertical nanoelectrodes have been developed to achieve highly sensitive, minimally invasive, and large scale intracellular recording. It has been demonstrated that the vertical geometry is crucial for the enhanced signal detection. Here we develop nanoelectrodes made up of nanotubes of iridium oxide. When cardiomyocytes are cultured upon those nanotubes, the cell membrane not only wraps around the vertical tubes but also protrudes deep into the hollow center. We show that this geometry enhances cell-electrode coupling and results in measuring much larger intracellular action potentials. The nanotube electrodes afford much longer intracellular access and are minimally invasive, making it possible to achieve stable recording up to an hour in a single session and more than 8 days of consecutive daily recording. This study suggests that the electrode performance can be significantly improved by optimizing the electrode geometry.