Multiple Electrode Array Research Articles

Interfacing Neuron-Motor Pathways with Stretchable and Biocompatible Electrode Arrays.

ConspectusIn the field of neuroscience, understanding the complex interactions within the intricate neuron-motor system depends crucially on the use of high-density, physiological multiple electrode arrays (MEAs). In the neuron-motor system, the transmission of biological signals primarily occurs through electrical and chemical signaling. Taking neurons for instance, when a neuron receives external stimuli, it generates an electrical signal known as the action potential. This action potential propagates along the neuron's axon and is transmitted to other neurons via synapses. At the synapse, chemical signals (neurotransmitters) are released, allowing the electrical signal to traverse the synaptic gap and influence the next neuron. MEAs can provide unparalleled insights into neural signal patterns when interfacing with the nerve systems through their excellent spatiotemporal resolution. However, the inherent differences in mechanical and chemical properties between these artificial devices and biological tissues can lead to serious complications after chronic implantation, such as body rejection, infection, tissue damage, or device malfunction. A promising strategy to enhance MEAs' biocompatibility involves minimizing their thickness, which aligns their bending stiffness with that of surrounding tissues, thereby minimizing damage over time. However, this solution has its limits; the resulting ultrathin devices, typically based on plastic films, lack the necessary stretchability, restricting their use to organs that neither stretch nor grow.For practical deployments, devices must exhibit certain levels of stretchability (ranging from 20 to 70%), tailored to the specific requirements of the target organs. In this Account, we outline recent advancements in developing stretchable MEAs that balance stretchability with sufficient electrical conductivity for effective use in physiological research, acting as sensors and stimulators. By concentrating on the neuron-motor pathways, we summarize how the stretchable MEAs meet various application needs and examine their effectiveness. We distinguish between on-skin and implantable uses, given their vastly different requirements. Within each application scope, we highlight cutting-edge technologies, evaluating their strengths and shortcomings. Recognizing that most current devices rely on elastic films with a Young's modulus value between ∼0.5 and 5 MPa, we delve into the potential for softer MEAs, particularly those using multifunctional hydrogels for an optimizing tissue-device interface and address the challenges in adapting such hydrogel-based MEAs for chronic implants. Additionally, transitioning soft MEAs from lab to fab involves connecting them to a rigid adapter and external machinery, highlighting a critical challenge at the soft-rigid interface due to strain concentration, especially in chronic studies subject to unforeseen mechanical strains. We discuss innovative solutions to this integration challenge, being optimistic that the development of durable, biocompatible, stretchable MEAs will significantly advance neuroscience and related fields.

Engineering human midbrain organoid microphysiological systems to model prenatal PFOS exposure

Perfluorooctane sulfonate (PFOS), a class of synthetic chemicals detected in various environmental compartments, has been associated with dysfunctions of the human central nervous system (CNS). However, the underlying neurotoxicology of PFOS exposure is largely understudied due to the lack of relevant human models. Here, we report bioengineered human midbrain organoid microphysiological systems (hMO-MPSs) to recapitulate the response of a fetal human brain to multiple concurrent PFOS exposure conditions. Each hMO-MPS consists of an hMO on a fully 3D printed holder device with a perfusable organoid adhesion layer for enhancing air-liquid interface culturing. Leveraging the unique, simply-fabricated holder devices, hMO-MPSs are scalable, easy to use, and compatible with conventional well-plates, and allow easy transfer onto a multiple-electrode array (MEA) system for plug-and-play measurement of neural activity. Interestingly, the neural activity of hMO-MPSs initially increased and subsequently decreased by exposure to a concentration range of 0, 30, 100, to 300 μM of PFOS. Furthermore, PFOS exposure impaired neural development and promoted neuroinflammation in the engineered hMO-MPSs. Along with PFOS, our platform is broadly applicable for studies toxicology of various other environmental pollutants.

Spatial distributions of electric field, temperature, and pH generated by multiple electrode arrays

Electrochemical therapy is used for cancer and its application is simple, safe, effective and induces minimal adverse effects to the body. It is not accepted as one more oncospecific therapy, among other reasons due to its lack of standardization. Therefore, the scientific problem of this research is that an electrode arrangement is not defined that maximizes tissue damage in the tumor with minimal damage to surrounding healthy tissue that allows its optimization for therapeutic planning and personalized therapy. The objective of the study is to simulate and compare the spatial distributions of the electric potential, electric field, temperature and tissue damage and pH generated by multiple pairs of electrodes that maximize the destruction of the tumor volume. It is concluded that the results suggest that multi-pair electrode configurations may be more effective for the treatment of large (diameter> 8 cm) and deep solid tumors.

Rapid and Robust Multi-Phenotypic Assay System for ALS Using Human iPS Cells with Mutations in Causative Genes.

Amyotrophic lateral sclerosis (ALS) is a major life-threatening disease caused by motor neuron degeneration. More effective treatments through drug discovery are urgently needed. Here, we established an effective high-throughput screening system using induced pluripotent stem cells (iPSCs). Using a Tet-On-dependent transcription factor expression system carried on the PiggyBac vector, motor neurons were efficiently and rapidly generated from iPSCs by a single-step induction method. Induced iPSC transcripts displayed characteristics similar to those of spinal cord neurons. iPSC-generated motor neurons carried a mutation in fused in sarcoma (FUS) and superoxide dismutase 1 (SOD1) genes and had abnormal protein accumulation corresponding to each mutation. Calcium imaging and multiple electrode array (MEA) recordings demonstrated that ALS neurons were abnormally hyperexcitable. Noticeably, protein accumulation and hyperexcitability were ameliorated by treatment with rapamycin (mTOR inhibitor) and retigabine (Kv7 channel activator), respectively. Furthermore, rapamycin suppressed ALS neuronal death and hyperexcitability, suggesting that protein aggregate clearance through the activation of autophagy effectively normalized activity and improved neuronal survival. Our culture system reproduced several ALS phenotypes, including protein accumulation, hyperexcitability, and neuronal death. This rapid and robust phenotypic screening system will likely facilitate the discovery of novel ALS therapeutics and stratified and personalized medicine for sporadic motor neuron diseases.

Optimizing electrode positions on forearm to increase SNR and myoelectric pattern recognition performance

With the advances in electromyography-based human–computer interaction, particularly in myoelectric prosthetic hands, the position of electromyography electrodes has gained less attention from researchers. However, the performance of hand movement recognition significantly varies with the change of electrode position around the forearm muscles and along the length of the forearm muscles. To find the robust position on the forearm, this study performs a comprehensive and systematic investigation of the feasibility of hand movement recognition using electromyogram (EMG) signals concurrently recorded for sixteen electrode arrays on the forearm. The obtained results indicate that the electrode array placed on the middle of the extensor digitorum communis and extensor digiti minimi performs better than other electrode positions around the forearm. In addition, multiple electrode arrays placed near to elbow joint achieve a significantly higher signal to noise ratio and signal to movement artifact ratio. In addition to improved EMG signal quality, the recommended positions on the forearm significantly overperform in hand movement recognition and it is validated with five well-known feature extraction methods, various window sizes, and three classification algorithms. In this study, the electrode arrays near to elbow joint on the forearm achieve an F1 score of 98.28% to 98.80% with a linear discriminant analysis classifier. Therefore, this study clearly demonstrates the feasibility of recommended forearm positions for hand movement recognition. As these electrode positions are near to elbow joint, so, it is expected that these positions will be available in most amputees and utilized for improved hand movement recognition.

Electrophysiological Activity of Primary Cortical Neuron-Glia Mixed Cultures.

Neuroinflammation plays a central role in many neurological disorders, ranging from traumatic brain injuries to neurodegeneration. Electrophysiological activity is an essential measure of neuronal function, which is influenced by neuroinflammation. In order to study neuroinflammation and its electrophysiological fingerprints, there is a need for in vitro models that accurately capture the in vivo phenomena. In this study, we employed a new tri-culture of primary rat neurons, astrocytes, and microglia in combination with extracellular electrophysiological recording techniques using multiple electrode arrays (MEAs) to determine the effect of microglia on neural function and the response to neuroinflammatory stimuli. Specifically, we established the tri-culture and its corresponding neuron-astrocyte co-culture (lacking microglia) counterpart on custom MEAs and monitored their electrophysiological activity for 21 days to assess culture maturation and network formation. As a complementary assessment, we quantified synaptic puncta and averaged spike waveforms to determine the difference in excitatory to inhibitory neuron ratio (E/I ratio) of the neurons. The results demonstrate that the microglia in the tri-culture do not disrupt neural network formation and stability and may be a better representation of the in vivo rat cortex due to its more similar E/I ratio as compared to more traditional isolated neuron and neuron-astrocyte co-cultures. In addition, only the tri-culture displayed a significant decrease in both the number of active channels and spike frequency following pro-inflammatory lipopolysaccharide exposure, highlighting the critical role of microglia in capturing electrophysiological manifestations of a representative neuroinflammatory insult. We expect the demonstrated technology to assist in studying various brain disease mechanisms.

Alzheimer’s Disease risk gene SORL1 affects synaptic function in hiPSC‐derived cortical neurons

AbstractBackgroundThe cellular endo‐lysosomal network (ELN) is implicated in Alzheimer’s Disease pathology and Sortilin‐related receptor 1 (SORL1) is important for normal function of the neuronal ELN. Loss of SORL1 in human induced pluripotent stem cell (hiPSC) derived neurons replicates early AD cytopathology, such as enlarged early endosomes. Work in our laboratory has shown that SORL1 deficiency results in decreased cell‐surface expression of glutamate receptor subunit GLUR1 and neurotrophic receptor TRKB. RNAseq of SORL1 deficient neurons revealed alterations in synaptic‐associated gene ontology transcripts. Together, these data implicate a potential functional consequence for SORL1 deletion. Here we investigate the impact of SORL1 on hiPSC‐derived neuronal synaptic function.MethodNeuronal cultures were differentiated using dual SMAD inhibition of previously generated wild‐type and SORL1 deficient hiPSCs. Following differentiation, neuronal cultures were either purified using cell surface markers CD44, CD184, and CD271 or passaged as mixed cultures for immunocytochemical (ICC) or electrophysiological experiments, respectively. For ICC, neurons were then fixed with paraformaldehyde and stained with experiment‐appropriate antibodies before imaging on a confocal scanning microscope. Mixed cultures were plated onto Axion Biosystems multiple electrode array (MEA) culture plates for electrophysiological analysis. MEA cultures were recorded twice a week for up to ten weeks post‐plating. Recordings and analysis were performed using Axion Biosystems Maestro Pro system.ResultUsing ICC, we find alterations in alterations in synaptic protein and glutamate receptor co‐localization in SORL1 deficient neuronal cultures. When cultured on MEA plates, wild‐type and SORL1 deficient neuronal cultures are active and robust. Neuronal cultures develop glutamate signaling dependent patterns of activity, or network bursting. Neural firing rates are increased in SORL1 deficient neurons. Network bursting properties in SORL1 deficient are altered in comparison to wild‐type cultures, consistent with increased neural excitability.ConclusionLoss of SORL1 alters hiPSC‐derived neuronal activity and synapse‐dependent activity. Further investigation is warranted into the alterations in neuronal physiology and will help us understand the role AD‐related ELN disruption plays in synaptic pathologies.

Proteomic profiling of human brain coupled to functional assays for the identification of neurotoxic proteins

AbstractBackgroundAlzheimer’s Disease (AD) affects millions globally, but therapy development is lagging. The dearth of new therapies requires a reconsideration of pre‐clinical models of AD to facilitate the discovery of efficacious treatments. Ideally, such models would allow for monitoring the functional behavior of neurons in conditions approximating the AD brain.MethodsTowards the goal of developing more representative, pre‐clinical AD models, we employ multiple‐electrode arrays (MEAs) and live‐cell imaging for assessing neuronal firing and neurite integrity (NI), respectively. We use this system to examine changes in neuronal activity and neurite integrity following treatment with TBS‐soluble human brain extract from a panel of 43 individuals comprised of AD patients, unaffected persons not exhibiting AD pathology nor cognitively impaired, and individuals not cognitively impaired but exhibited AD‐related postmortem pathology. To determine the molecular etiology of these functional changes in an unbiased manner, we perform label‐free proteomic analyses on the panel of 43 brain extracts.ResultsAmyloid‐β (Aβ) and tau accumulate in the AD brain, and specific forms of each of these proteins have shown neurotoxic properties. We observe associations between spontaneous activity and Aβ42:40 levels, and between neurite integrity and oligomeric Aβ or tau containing N inserts. Additionally, the proteomic analyses reveal several candidates whose expression correlated with changes in neuronal structure and activity. Proteins associated with neurotoxic activities in MEA and NI assays are enriched in proteins implicated in lysosomal storage disorders, while proteins associated with neuroprotective properties are enriched in proteins of the WAVE regulatory complex that are involved in the regulation of actin polymerization. We further show that elevated GM2A in the AD brain and AD CSF is associated with reductions in both neurite integrity and MEA activity. Applying cell derived GM2A in the absence of brain extract is sufficient to induce a subtle but significant loss of neurite integrity.ConclusionThe techniques and data herein introduce a system for modeling neuronal vulnerability in response to factors present in the aged human brain and provide insights into proteins potentially contributing to AD pathogenesis.

Microglial WNT5A supports dendritic spines maturation and neuronal firing

There is increasing evidence showing that microglia play a critical role in mediating synapse formation and spine growth, although the molecular mechanism remains elusive. Here, we demonstrate that the secreted morphogen WNT family member 5A (WNT5A) is the most abundant WNT expressed in microglia and that it promotes neuronal maturation. Co-culture of microglia with Thy1-YFP+ differentiated neurons significantly increased neuronal spine density and reduced dendritic spine turnover rate, which was diminished by silencing microglial Wnt5a in vitro. Co-cultured microglia increased post-synaptic marker PSD95 and synaptic density as determined by the co-localization of PSD95 with pre-synaptic marker VGLUT2 in vitro. The silencing of Wnt5a expression in microglia partially reduced both PSD95 and synaptic densities. Co-culture of differentiated neurons with microglia significantly enhanced neuronal firing rate as measured by multiple electrode array, which was significantly reduced by silencing microglial Wnt5a at 23 days differentiation in vitro. These findings demonstrate that microglia can mediate spine maturation and regulate neuronal excitability via WNT5A secretion indicating possible pathological roles of dysfunctional microglia in developmental disorders.

Abstract 12044: Injectable Contraceptive, Medroxyprogesterone Acetate, Produces Erratic Beating Patterns in Patient-Specific Re-Engineered Heart Cells With Type 2 Long QT Syndrome

Background: Type 2 long QT syndrome (LQT2) is an inherited arrhythmia syndrome caused by pathogenic variants in the KCNH2 gene which result in QT prolongation and confers susceptibility to arrhythmic syncope/seizures and sudden cardiac arrest/death. Oral progestin-based contraceptives increase the risk of cardiac events in women with LQT2 and we previously reported the case of a LQT2 woman with recurrent cardiac events attributed to the use of the progestin-based contraceptive, Medroxyprogesterone Acetate (“Depo-Provera”, Depo). Objective: To evaluate the arrhythmic-risk of Depo in a LQT2-specific, induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) model. Methods: An iPSC-CM line was generated from the previously reported woman (KCNH2-G1006A*fs) as well as a control line. Voltage-sensing dye was used to assess the optical action potential duration (APD) with 10 μM Depo. 3-D erratic beating patterns were then assessed using multiple electrode array (MEA) with Depo and isoproterenol (ISO) to mimic an adrenergic surge. Results: Addition of Depo to the G1006A*fs iPSC-CMs decreased the optical APD from baseline 438±14 ms (n=6) to 363±35 ms (n=12; p=0.0001). Despite the APD shortening at baseline, in the setting of ISO, Depo administration induced erratic beating patterns in MEA, characterized as alternating spike amplitudes, alternans, or early after depolarization-like phenomena. Combined Depo and ISO treatment increased the percent of electrodes displaying erratic beating in G1006A*fs [baseline 8%±13 vs. Depo + ISO 38%±40 (p=0.0097)] but not in controls [baseline 2%±5 vs. Depo + ISO 7%±11 (p=0.14)]. Neither Depo nor ISO alone changed beating patterns in G1006A*fs [baseline 8%±13, Depo 30%±41 (p=0.08), ISO 21%±30, (p=0.17)] and controls [baseline 2%±5, Depo 3%±7 (p=0.61), ISO 0%±0 (p=0.4)]. Conclusion: This patient-specific, re-engineered heart cell study provides a potential mechanism for the patient’s clinically documented, Depo-associated episodes of recurrent ventricular fibrillation. This in-vitro data should prompt a large-scale clinical assessment of Depo’s potential pro-arrhythmic effect in women with LQT2.

Mild membrane depolarization in neurons induces immediate early gene transcription and acutely subdues responses to a successive stimulus

Immediate early genes (IEGs) are transcribed in response to neuronal activity from sensory stimulation during multiple adaptive processes in the brain. The transcriptional profile of IEGs is indicative of the duration of neuronal activity, but its sensitivity to the strength of depolarization remains unknown. Also unknown is whether activity history of graded potential changes influence future neuronal activity. In this work with dissociated rat cortical neurons, we found that mild depolarization—mediated by elevated extracellular potassium (K+)—induces a wide array of rapid IEGs and transiently depresses transcriptional and signaling responses to a successive stimulus. This latter effect was independent of de novo transcription, translation, and signaling via calcineurin or mitogen-activated protein kinase. Furthermore, as measured by multiple electrode arrays and calcium imaging, mild depolarization acutely subdues subsequent spontaneous and bicuculline-evoked activity via calcium- and N-methyl-d-aspartate receptor–dependent mechanisms. Collectively, this work suggests that a recent history of graded potential changes acutely depress neuronal intrinsic properties and subsequent responses. Such effects may have several potential downstream implications, including reducing signal-to-noise ratio during synaptic plasticity processes.

Adaptation of the Two-CAP Method for Conduction Velocity Distribution Estimation in Multi-Channel Recordings.

Closed-loop neural interfaces capable of both stimulating and recording from peripheral nerves have the potential to enhance the long-term efficacy of neural implants. One challenge associated with closed loop interfaces is the accurate estimation of the distribution of active fibre conduction velocities (DCV) when recording the immediate effect of stimulation. DCV estimation has been performed in monopolar surface recordings using the Two-CAP method. This work extends the Two-CAP method and demonstrates its application to bipolar in-vivo recordings made with multiple-electrode arrays. A sensitivity analysis was conducted using simulated data with ground truth to ascertain the stability and limits of the algorithm before experimental data was examined. The sensitivity analysis highlighted that recording distance shows a considerable impact on the performance of this extended Two-CAP method, as well as the velocity interval chosen when creating the model. The in-vivo data was also compared against an equivalent simulated model, and a relatively low mean squared error was obtained when comparing the two distributions.

Neural representation in M1 and S1 cortex of bilateral hand actions during prehension.

Bimanual movements that require coordinated actions of the two hands may be coordinated by synchronous bilateral activation of somatosensory and motor cortical areas in both hemispheres, by enhanced activation of individual neurons specialized for bimanual actions, or by both mechanisms. To investigate cortical neural mechanisms that mediate unimanual and bimanual prehension, we compared actions of the left and right hands in a reach to grasp-and-pull instructed-delay task. Spike trains were recorded with multiple electrode arrays placed in the hand area of primary motor (M1) and somatosensory (S1) cortex of the right hemisphere in macaques, allowing us to measure and compare the relative timing, amplitude, and synchronization of cortical activity in these areas as animals grasped and manipulated objects that differed in shape and location. We report that neurons in the right hemisphere show common task-related firing patterns for the two hands but actions of the ipsilateral hand elicited weaker and shorter-duration responses than those of the contralateral hand. We report significant bimanual activation of neurons in M1 but not in S1 cortex when animals have free choice of hand use in prehension tasks. Population ensemble responses in M1 thereby provide an accurate depiction of hand actions during skilled manual tasks. These studies also demonstrate that somatosensory cortical areas serve important cognitive and motor functions in skilled hand actions. Bilateral representation of hand actions may serve an important role in "motor equivalence" when the same movements are performed by either hand and in transfer of skill learning between the hands.NEW & NOTEWORTHY Humans can manipulate small objects with the right or left hand but typically select the dominant hand to handle them. We trained monkeys to grasp and manipulate objects with either hand, while recording neural activity in primary motor (M1) and somatosensory (S1) cortex. Actions of both hands activate M1 neurons, but S1 neurons respond only to the contralateral hand. Bilateral sensitivity in M1 may aid skill transfer between hands after stroke or head injury.

Human Spinal Organoid-on-a-Chip to Model Nociceptive Circuitry for Pain Therapeutics Discovery.

The discovery of new pain therapeutics targeting human nociceptive circuitry is an emerging, exciting, and rewarding field. However, current models for evaluating prospective new therapeutics [e.g., animals and two-dimensional (2D) in vitro cultures] fail to fully recapitulate the complexity of human nociceptive neuron and dorsal horn neuron biology, significantly limiting the development of novel pain therapeutics. Here, we report human spinal organoid-on-a-chip devices for modeling the biology and electrophysiology of human nociceptive neurons and dorsal horn interneurons in nociceptive circuitry. Our device can be simply made through the integration of a membrane with a three-dimensional (3D)-printed organoid holder. By combining air-liquid interface culture and spinal organoid protocols, our devices can differentiate human stem cells into human sensori-spinal-cord organoids with dorsal spinal cord interneurons and sensory neurons. By easily transferring from culture well plates to the multiple-electrode array (MEA) system, our device also allows the plug-and-play measurement of organoid activity for testing nociceptive modulators (e.g., mustard oil, capsaicin, velvet ant venom, etc.). Our organoid-on-a-chip devices are cost-efficient, scalable, easy to use, and compatible with conventional well plates, allowing the plug-and-play measurement of spinal organoid electrophysiology. By the integration of human sensory-spinal-cord organoids with our organoid-on-a-chip devices, our method may hold the promising potential to screen and validate novel therapeutics for human pain medicine discovery.

Zfhx3 modulates retinal sensitivity and circadian responses to light.

Mutations in transcription factors often exhibit pleiotropic effects related to their complex expression patterns and multiple regulatory targets. One such mutation in the zinc finger homeobox 3 (ZFHX3) transcription factor, short circuit (Sci, Zfhx3Sci/+ ), is associated with significant circadian deficits in mice. However, given evidence of its retinal expression, we set out to establish the effects of the mutation on retinal function using molecular, cellular, behavioral and electrophysiological measures. Immunohistochemistry confirms the expression of ZFHX3 in multiple retinal cell types, including GABAergic amacrine cells and retinal ganglion cells including intrinsically photosensitive retinal ganglion cells (ipRGCs). Zfhx3Sci/+ mutants display reduced light responsiveness in locomotor activity and circadian entrainment, relatively normal electroretinogram and optomotor responses but exhibit an unexpected pupillary reflex phenotype with markedly increased sensitivity. Furthermore, multiple electrode array recordings of Zfhx3Sci/+ retina show an increased sensitivity of ipRGC light responses.

Generation of region-specific and high-purity neurons from human feeder-free iPSCs

Human induced pluripotent stem cells (iPSCs) have great potential to elucidate the molecular pathogenesis of neurological/psychiatric diseases. In particular, neurological/psychiatric diseases often display brain region-specific symptoms, and the technology for generating region-specific neural cells from iPSCs has been established for detailed modeling of neurological/psychiatric disease phenotypes in vitro. On the other hand, recent advances in culturing human iPSCs without feeder cells have enabled highly efficient and reproducible neural induction. However, conventional regional control technologies have mainly been developed based on on-feeder iPSCs, and these methods are difficult to apply to feeder-free (ff) iPSC cultures. In this study, we established a novel culture system to generate region-specific neural cells from human ff-iPSCs. This system is the best optimized approach for feeder-free iPSC culture and generates specific neuronal subtypes with high purity and functionality, including forebrain cortical neurons, forebrain interneurons, midbrain dopaminergic neurons, and spinal motor neurons. In addition, the temporal patterning of cortical neuron layer specification in the forebrain was reproduced in our culture system, which enables the generation of layer-specific cortical neurons. Neuronal activity was demonstrated in the present culture system by using multiple electrode array and calcium imaging. Collectively, our ff-iPSC-based culture system would provide a desirable platform for modeling various types of neurological/psychiatric disease phenotypes.

Variability of seizure-like activity in an in vitro model of epilepsy depends on the electrical recording method

BackgroundHippocampal and cortical slice-based models are widely used to study seizures and epilepsy. Seizure detection and quantification are essential components for studying mechanisms of epilepsy and assessing therapeutic interventions. To obtain meaningful signals and maximize experimental throughput, variability should be minimized. Some electrical recording methods require insertion of an electrode into neuronal tissue, change in slice chemical microenvironment, and transients in temperature and pH. These perturbations can cause acute and long-term alterations of the neuronal network which may be reflected in the variability of the recorded signal. New methodIn this study we investigated the effect of experimental perturbations in three local field potential (LFP) recording methods including substrate micro-wires (s-MWs), multiple electrode arrays (MEAs), and inserted micro wire electrodes (i-MW). These methods enabled us to isolate effects of different perturbations. We used organotypic hippocampal slices (OHCs) as an in-vitro model of posttraumatic epilepsy. To investigate the effect of the disturbances caused by the recording method on the paroxysmal events, we introduced jitter analysis, which is sensitive to small differences in the seizure spike timing. ResultsMedium replacement can introduce long-lasting perturbations. Electrode insertion increased variability on a shorter time scale. OHCs also underwent spontaneous state transitions characterized by transient increases in variability. Comparison with existing methodsThis new method of seizure waveform analysis allows for more sensitive assessment of variability of ictal events than simply measuring seizure frequency and duration. ConclusionWe demonstrated that some of the variability in OHC recordings are due to experimental perturbations while some are spontaneous and independent of recording method.

Creating Custom Neural Circuits on Multiple Electrode Arrays Utilizing Optical Tweezers for Precise Nerve Cell Placement

Precise creation, maintenance, and monitoring of neuronal circuits would facilitate the investigation of subjects such as neuronal development or synaptic plasticity, or assist in the development of neuronal prosthetics. Here we present a method to precisely control the placement of multiple types of neuronal retinal cells onto a commercially available multiple electrode array (MEA), using custom-built optical tweezers. We prepared the MEAs by coating a portion of the MEA with a non-adhesive substrate (Poly (2-hydroxyethyl methacrylate)), and the electrodes with an adhesive cell growth substrate. We then dissociated the retina of adult tiger salamanders, plated them onto prepared MEAs, and utilized the optical tweezers to create retinal circuitry mimicking in vivo connections. In our hands, the optical tweezers moved ~75% of photoreceptors, bipolar cells, and multipolar cells, an average of ~2000 micrometers, at a speed of ~16 micrometers/second. These retinal circuits were maintained in vitro for seven days. We confirmed electrophysiological activity by stimulating the photoreceptors with the MEA and measuring their response with calcium imaging. In conclusion, we have developed a method of utilizing optical tweezers in conjunction with MEAs that allows for the design and maintenance of custom neural circuits for functional analysis.

Engineering of brain-like tissue constructs via 3D Cell-printing technology

The development of 3D Cell-printing technology contributes to the application of tissue constructs in vitro in neuroscience. Collecting neural cells from patients is an efficient way of monitoring health of an individual target, which, in turn, benefits the enhancement of medicines. The fabricated sample of neural cells is exposed to potential drugs for the analysis of neuron responses. 3D cell-printing as an emerging biofabrication technology has been widely used to mimic natural 3D models in in vitro tissue research, especially in vitro brain-like tissue constructs in neuroscience. Fabricated brain-like tissue constructs provide a 3D microenvironment for primary neural cells to grow within. After more than several weeks of in vitro culturing, the formation of neural circuits in structures equips them with the capability of sensitively responding to a stimulus. In this study, an in vitro layered brain-like tissue construct is first proposed and later developed by 3D cell-printing technology. The layered structure is systematically analyzed, starting from printing parameter optimization to biological functionality performance. The optimized diameter of printing nozzle and printing speed are 0.51 mm and 5 μl s−1, respectively, and the elastic modulus is approximately 6 kPa. Live/dead and immunostaining imaging is used to verify the growth of neural cells in the printed structure. The survival rate of neural cells in 2D and 3D samples is compared, and the results demonstrate that the 3D-printed structures exhibit a better artificial culturing environment and a higher survival rate. Both 2D and 3D samples are directly cultured in a 4 × 4 multiple electrode array. Local field potentials are collected and validated by the Med64 recording system. Tetrodotoxin is used to test the drug sensitivity of the printed structure, and the excitatory postsynaptic potential signals of the physiological performance indicate that the 3D-printed structure has great potential as a drug testing model in the pharmaypeceutical study.

Efficacy of direct current generated by multiple-electrode arrays on F3II mammary carcinoma: experiment and mathematical modeling

BackgroundThe modified Gompertz equation has been proposed to fit experimental data for direct current treated tumors when multiple-straight needle electrodes are individually inserted into the base perpendicular to the tumor long axis. The aim of this work is to evaluate the efficacy of direct current generated by multiple-electrode arrays on F3II mammary carcinoma that grow in the male and female BALB/c/Cenp mice, when multiple-straight needle electrodes and multiple-pairs of electrodes are inserted in the tumor.MethodsA longitudinal and retrospective preclinical study was carried out. Male and female BALB/c/Cenp mice, the modified Gompertz equation, intensities (2, 6 and 10 mA) and exposure times (10 and 20 min) of direct current, and three geometries of multiple-electrodes (one formed by collinear electrodes and two by pair-electrodes) were used. Tumor volume and mice weight were measured. In addition, the mean tumor doubling time, tumor regression percentage, tumor growth delay, direct current overall effectiveness and mice survival were calculated.ResultsThe greatest growth retardation, mean doubling time, regression percentage and growth delay of the primary F3II mammary carcinoma in male and female mice were observed when the geometry of multiple-pairs of electrodes was arranged in the tumor at 45, 135, 225 and 325o and the longest exposure time. In addition, highest direct current overall effectiveness (above 66%) was observed for this EChT scheme.ConclusionsIt is concluded that electrochemical therapy may be potentially addressed to highly aggressive and metastic primary F3II murine mammary carcinoma and the modified Gompertz equation may be used to fit data of this direct current treated carcinoma. Additionally, electrochemical therapy effectiveness depends on the exposure time, geometry of multiple-electrodes and ratio between the direct current intensity applied and the polarization current induced in the tumor.