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Microelectrodes have applications in EDM drilling and milling to fabricate microholes and microchannels. Moving Block Electrical Discharge Turning (MB-EDT) is a technique used to manufacture these microelectrodes. Gaseous dielectrics in EDM are critical due to their environmental friendly characteristics. Process optimization of microelectrode fabrication requires consideration of both electrical and non-electrical factors. This study investigated the impact of non-electrical factors on MRR and surface roughness of fabricated microelectrodes. A statistical model was established successfully for each response. Dielectric pressure significantly influences, contributing 57.78% to MRR and 42.77% to Ra. Using a multi-objective genetic algorithm, optimal parameters were identified for spindle rotation speed at 412 rpm, block linear feed rate at 7.36 mm/sec, and dielectric pressure at 6.4 bar for a maximum MRR of 0.0087 μm3/min and minimal Ra of 0.6138 μm. SEM micrographs illustrate improved surface uniformity at higher process factor levels, underscoring the optimization's effectiveness in enhancing microelectrode quality. [ABSTRACT FROM AUTHOR]

Microelectrodes play a crucial role in microfluidic chips. However, electrodes with micron‐sized geometries lead to undesired impedance increases and processing difficulties. This study introduces a method for preparing low‐resistance and low‐cost liquid metal microelectrodes (μLMEs$\umu{\rm LMEs}$), which leverages the distinct phase transition properties of liquid metal (LM) gallium (Ga) and Poly‐N‐Isopropylacrylamide (PNIPAM), along with the reversible bonding between PNIPAM and polydimethylsiloxane (PDMS). PNIPAM is spin‐coated as a sacrificial layer on silanized glass and heated to dehydration. As it hydrates and swells in the water bath, Ga/PDMS can be easily peeled off, forming a precision surface‐embedded μLME$\umu{\rm LME}$. The resistance of the μLME$\umu{\rm LME}$ with a thickness of 25 μm$\umu{\rm m}$ was only 9.3% and 0.077% of the 100nm thin film Au and indium tin oxide (ITO) film microelectrode with the same plane size. Hydration and swelling of the sacrificial layer ensured the fabrication with high resolutions down to 5 μm$\umu{\rm m}$ and an acute angle of 15°. The electroosmotic flow tests show that the μLME$\umu{\rm LME}$ effectively reduces the operating voltage compared to conventional planar Au or ITO microelectrodes. These features make it a promising candidate for electrification requirements in microfluidic devices. [ABSTRACT FROM AUTHOR]

Various organic compounds susceptible to anodic polymerization were selected to study the effects of two solvents: acetic acid and ethyl acetate. Phenol and most of its derivatives, as well as resorcinol and 3,5-dihydroxybenzoic acid, exhibited typical electrode deactivation similar to other solvents; however, a continuous decrease in peak currents was not observed for 4-tert-butylphenols or salicylic aldehyde. Similar behavior was noted for monomers unrelated to phenols. In general, peaks were observed only for certain compounds and not in the initial voltammogram. Significant differences between the two solvents were observed in the subsequent voltammetric curves for some monomers. Microelectrode studies using 4-methoxyphenol as a model compound revealed notable differences between acetic acid and ethyl acetate in terms of curve shapes and the onset potentials of the plateaus. Plateau currents were used to estimate the solvent composition, demonstrating relatively high sensitivity to the acetic acid content. [ABSTRACT FROM AUTHOR]

An electrochemical investigation of 1,2- and 1,4-dihydroxybenzenes was carried out with platinum macro- and microelectrodes using square wave and cyclic voltammetry techniques. Furthermore, the effect of the two solvents—acetic acid and ethyl acetate—was compared. When using square wave voltammetry, signals only appeared at lower frequencies and only when the supporting electrolyte was in excess, as expected due to the relatively low permittivity of the used solvents. The behavior of hydroquinone and catechol did not differ significantly from that of their derivatives (dihydroxybenzaldehydes, dihydroxybenzoic acids and 2′,5′-dihydroxyacetophenone). When the cyclic voltammetric experiments using a microelectrode were extended to higher anodic potentials, electrode fouling was very significant in ethyl acetate after the potential region where steady-state oxidation to the corresponding quinone occurs. The substituent effect was not significant here either, which was proven by using different functional groups in different positions. In contrast, the position had a dramatic influence on the susceptibility to electropolymerization, as 1,2-dihydroxybenzenes—independent of the nature of the substituent on the benzene ring—deactivated the electrode, while 1,4-dihydroxybenzenes did not, possibly due to the different solubilities of the polymers formed from the primary oxidation product (quinones). A user-friendly analytical procedure is also proposed that uses an electropolymerization reaction and does not require frequent cleaning of the electrode via polishing, which is required usually especially with a microelectrode. [ABSTRACT FROM AUTHOR]

Introduction: Vagus nerve stimulation (VNS) is an effective treatment for people with drug‐resistant epilepsy. However, its mechanisms of action are poorly understood, including which nerve fibers are activated in humans during VNS in typical clinical settings and which are required for clinical efficacy. In particular, there have been no intraneural recordings of vagus nerve fiber activation in awake humans undergoing chronic VNS. In this study, for the first time, we report recordings from the vagus nerve in this setting. Methods: The recordings were performed using a sterile tungsten microelectrode inserted percutaneously into the cervical vagus nerve under ultrasound guidance. The clinical VNS systems were used to deliver stimulation while activity in the vagus nerve was recorded. Results: In addition to activating myelinated axons at low currents, we provide evidence that VNS can also activate unmyelinated C fibers in the vagus nerve at currents <1 mA. Conclusions: These results add to our understanding of how VNS exerts its beneficial effects in drug‐resistant epilepsy. Plain Language Statement: Here we describe for the first time, electrical recordings from the vagus nerve in awake drug‐resistant epilepsy patients with an implanted vagus nerve stimulation (VNS) device. We found that the VNS device was able to activate both myelinated and unmyelinated fibers within the vagus nerve, which contributes to our understanding of how VNS works in the context of drug‐resistant epilepsy. [ABSTRACT FROM AUTHOR]

The interaction between redox-active species and dissolved organic carbon (DOC) is crucial in driving lacustrine benthic microbial processes. In lacustrine porewaters, many redox-active species exist in their reduced form, while DOC acts as a substrate and an electron acceptor. Understanding the types and abundance of redox-active species in porewaters along with their complementary DOC substrate is pivotal for gaining insights into benthic processes, particularly in regions susceptible to climate change. We report the in-situ measurement of redox-active species in sediment porewaters, alongside the ex-situ measurement of DOC extracted from cores collected from two Arctic lakes (Toolik and Fog 1). Fe2+ was abundantly detected below 4 cm of the sediment-water interface in all cores and was inversely related to dissolved O2. Additionally, two distinct Fe(III)-complexes were identified. DOC ranged in the order of 10s of mg/L and either remained stable or increased with depth. A comparison between Toolik and Fog 1 lakes revealed a higher accumulation of Fe2+ and DOC in the latter. This study marks the first of its kind to assess spatial distributions of redox-active species and DOC as a function of depth from multiple sites in Arctic lacustrine porewaters. [ABSTRACT FROM AUTHOR]

Abstract Introduction Vagus nerve stimulation (VNS) is an effective treatment for people with drug‐resistant epilepsy. However, its mechanisms of action are poorly understood, including which nerve fibers are activated in humans during VNS in typical clinical settings and which are required for clinical efficacy. In particular, there have been no intraneural recordings of vagus nerve fiber activation in awake humans undergoing chronic VNS. In this study, for the first time, we report recordings from the vagus nerve in this setting. Methods The recordings were performed using a sterile tungsten microelectrode inserted percutaneously into the cervical vagus nerve under ultrasound guidance. The clinical VNS systems were used to deliver stimulation while activity in the vagus nerve was recorded. Results In addition to activating myelinated axons at low currents, we provide evidence that VNS can also activate unmyelinated C fibers in the vagus nerve at currents

Integrated multi-trophic aquaculture has attracted widespread attention and is considered an effective way to purify the water environment and improve the sustainability of aquaculture. However, the biodeposition produced by large-scale, high-density raft-type shellfish and seaweed aquaculture activities has been shown to be the main reason for the enrichment of organic matter in sediments. Organic matter enrichment changes the biogeochemistry of sediment, which is the main reason for hypoxia in the benthic environment. Especially in the summer, water column stratification in terms of water and salinity can lead to hypoxia in the benthic environment. Besides, the hypoxic conditions in sediment promote anaerobic metabolism and sulfate reduction, which increase the dissolved sulfide concentration in the interstitial water. It was reported that dissolved oxygen (DO) in the sediment is depleted within a range of a few millimeters to a few centimeters in surface sediments. The diffusion boundary layer (DBL), which generally varies between a tenth of a millimeter and a few millimeters above the sediment, greatly influences substance exchange across the sediment-water interface. Current studies on the environmental effect of aquaculture mainly focus on the influence of aquaculture activities on the environment, and the influence mechanism of aquaculture activities on the sediment microenvironment remains unknown. Therefore, it is necessary to study the influence of aquaculture activities on the sediment microenvironment and to explore the influence mechanism of aquaculture activities on the distribution of physical and chemical factors in the sediment microenvironment.In this study, microscale variations in the distribution and consumption of oxygen at the sediment-water interface under high temperature conditions was investigated in the summer of 2022 in Sanggou Bay, a typical integrated multi-trophic aquaculture area in northern China. A high-resolution microelectrode system was used to investigate the profile distributions of DO, hydrogen sulfide (H2S), and pH in sediments with a spatial resolution of 1 mm collected from the shellfish monoculture area (SF), shellfish and seaweed polyculture area (SF-SW), seaweed monoculture area (SW), and offshore area (OF). The thickness of the DBL of different aquaculture areas was determined according to the DO distribution at the sediment-water interface and the inflection point of the profile distribution. Sediment cores were sliced at a thickness of 1 cm and the profile distribution of sediment organic carbon, the median grain size, and other factors in the surface sediment in different aquaculture areas were measured. The diffusive oxygen flux at the water-sediment interface was calculated from the gradient of the DO concentration in the DBL, and the sediment oxygen consumption rate in different aquaculture areas was calculated from the DO profile distribution in the sediment.The results showed that the mean thickness of the DBL in the SF, SF-SW, SW, and OF areas were (1.5±0.3), (1.0±0.3), (2.0±0.8), and (1.3±0.2) mm, respectively; there was no significant difference between different aquaculture areas. The mean sediment oxygen penetration depth (OPD) was (12.49±1.59), (12.17±0.09), (15.49±0.79), and (14.87±1.27) mm, respectively. The sediment OPDs in the SF-SW and SF areas were significantly lower than those in the SW and OF areas. The maximum concentrations of H2S were (5.73±0.04), (4.80±0.08), (3.30±0.19), and (3.97±0.38) μmol/L, respectively. The mean diffusive oxygen flux in the SF, SF-SW, SW, and OF areas were (24.10±1.89), (49.53±10.24), (26.69±13.13), and (24.79±7.95) mmol/(m2·d), respectively. The diffusive oxygen flux in the shellfish and kelp polyculture area was significantly higher than that in other areas. The diffusive oxygen flux at the sediment-water interface was affected by the DO concentration of the overlying water and the sediment oxygen consumption rate. The diffusive oxygen flux in the SF area was influenced by the thickness of the DBL, the DO concentration of the overlying water, and the DO concentration at the sediment-water interface. The main factor influencing the diffusive oxygen flux in the SW and SF-SW areas was the DO concentration of the overlying water.In conclusion, the biodeposition produced by aquaculture activities significantly affects material cycling in surface sediments, which promotes sediment oxygen consumption and the production of hydrogen sulfide. The influence of biodeposition produced by shellfish farming on the sediment chemical characteristics and microprofiles may be stronger than that of kelp debris. The DO concentration of the water environment is the main reason affecting organic matter mineralization in the sediments of aquaculture areas. This study also provides scientific and technological support for an in-depth understanding of the influence of aquaculture on the sediment microenvironment and the benthic carbon cycle.

The design and development of new and efficient catalyst binder materials are important for improving cell performance in high‐temperature proton‐exchange membrane fuel cells (HT‐PEMFCs). In this study, a series of tetrafluorophenyl phosphonic acid−based binder materials (PF‐y‐P, y=1, 0.83, and 0.67) with rigid structures and controllable degrees of phosphonation were prepared and used in HT‐PEMFCs using the ultra‐strong acid‐catalyzed Friedel−Crafts reaction and the combined Michaelis−Arbuzov reaction. The samples exhibited high stability, low water uptake, superior proton conductivity, and cell performance. In addition, the oxygen mass transport properties of the PF‐1‐P binder were investigated using high‐temperature microelectrode electrochemical testing techniques. Compared with the phosphoric acid‐doped polybenzimidazole (PBI) binder, the O2 solubility of PF‐1‐P binder material increased by 30 % (5.36×10−6 mol cm−3) and the PF‐1‐P binder material exhibited better cell stability in HT‐PEMFCs. After 10.5 h of discharge at a constant current of 0.12 A cm−2, the MEA voltage decreased by 7.1 % and 20.8 % in case of the PF‐1‐P and PBI binders, respectively. [ABSTRACT FROM AUTHOR]

In this study, glucose oxidase (GOx) was immobilized on the electrode surface by layer‐by‐layer and gel membrane technique and characterized the GOx immobilized film morphology, H2O2 permeability, and glucose response. Concanavalin A (Con A)‐GOx multilayer electrodes showed higher glucose‐related current response than GOx‐bovine serum albumin gel membrane‐coated electrode, a common modification method. The thin thickness of the Con A/GOx multilayer film efficiently catalyzed the enzymatic reaction, and H2O2 was produced near the electrode surface, resulting in an immediate electrode response. [ABSTRACT FROM AUTHOR]

The interaction between redox-active species and dissolved organic carbon (DOC) is crucial in driving lacustrine benthic microbial processes. In lacustrine porewaters, many redox-active species exist in their reduced form, while DOC acts as a substrate and an electron acceptor. Understanding the types and abundance of redox-active species in porewaters along with their complementary DOC substrate is pivotal for gaining insights into benthic processes, particularly in regions susceptible to climate change. We report the in-situ measurement of redox-active species in sediment porewaters, alongside the ex-situ measurement of DOC extracted from cores collected from two Arctic lakes (Toolik and Fog 1). Fe2+ was abundantly detected below 4 cm of the sediment-water interface in all cores and was inversely related to dissolved O2. Additionally, two distinct Fe(III)-complexes were identified. DOC ranged in the order of 10s of mg/L and either remained stable or increased with depth. A comparison between Toolik and Fog 1 lakes revealed a higher accumulation of Fe2+ and DOC in the latter. This study marks the first of its kind to assess spatial distributions of redox-active species and DOC as a function of depth from multiple sites in Arctic lacustrine porewaters.

Visual electrophysiology measurements are crucial in ophthalmology as they are frequently used for diagnosing and treating numerous ocular diseases. Therefore, optically transparent and flexible electrodes with high sensitivity at localized regions are in high demand. Here, it is aimed to develop a soft, transparent, multi‐electrode system assembled on commercially available soft contact lenses and assess its application in measuring Electroretinography (ERG) responses in rabbits. A biocompatible multi‐electrode system on commercial disposable soft contact lenses is successfully constructed, showing 95% cell viability, 82% optical transparency over the visible range, and good flexibility at 10% strain. Direct current (DC) voltage is used to produce a highly resistive overoxidized poly(3,4‐ethylenedioxythiophene) (PEDOT) layer that covers all parts of the electrodes except the sensing region, which, owing to its high conductivity, can accurately measure electrical signals from local regions of the cornea. Spatially resolved ERG recordings of rabbits are obtained with superior signal quality using this multi‐electrode system. Thus, this device is expected to be used in ophthalmic diagnosis in the future. [ABSTRACT FROM AUTHOR]

pH has been considered one of the paramount factors in bodily functions because most cellular tasks exclusively rely on precise pH values. In this context, the current techniques for pH sensing provide us with the futuristic insight to further design therapeutic and diagnostic tools. Thus, pH‐sensing (electrochemically and optically) is rapidly evolving toward exciting new applications and expanding researchers' interests in many chemical contexts, especially in biomedical applications. The adaptation of cutting‐edge technology is subsequently producing the modest form of these biosensors as wearable devices, which are providing us the opportunity to target the real‐time collection of vital parameters, including pH for improved healthcare systems. The motif of this review is to provide insight into trending tech‐based systems employed in real‐time or in‐vivo pH‐responsive monitoring. Herein, we briefly go through the pH regulation in the human body to help the beginners and scientific community with quick background knowledge, recent advances in the field, and pH detection in real‐time biological applications. In the end, we summarize our review by providing an outlook; challenges that need to be addressed, and prospective integration of various pH in vivo platforms with modern electronics that can open new avenues of cutting‐edge techniques for disease diagnostics and prevention. [ABSTRACT FROM AUTHOR]

Dopamine (DA), ascorbic acid (AA), and uric acid (UA) are crucial neurochemicals, and their abnormal levels are involved in various neurological disorders. While electrodes for their detection have been developed, achieving the sensitivity required for in vivo applications remains a challenge. In this study, we proposed a synthetic Au24Cd nanoenzyme (ACNE) that significantly enhanced the electrochemical performance of metal electrodes. ACNE-modified electrodes demonstrated a remarkable 10-fold reduction in impedance compared to silver microelectrodes. Furthermore, we validated their excellent electrocatalytic activity and sensitivity using five electrochemical detection methods, including cyclic voltammetry, differential pulse voltammetry, square-wave pulse voltammetry, normal pulse voltammetry, and linear scanning voltammetry. Importantly, the stability of gold microelectrodes (Au MEs) modified with ACNEs was significantly improved, exhibiting a 30-fold enhancement compared to Au MEs. This improved performance suggests that ACNE functionalization holds great promise for developing micro-biosensors with enhanced sensitivity and stability for detecting small molecules. [ABSTRACT FROM AUTHOR]

Abstract In the context of wound healing and tissue regeneration, precise control of cell migration direction is deemed crucial. To address this challenge, polydimethylsiloxane (PDMS) platforms with patterned 10 nm thick TiOx in arrowhead shape were designed and fabricated. Remarkably, without tall sidewall constraints, MC3T3-E1 cells seeded on these platforms were constrained to migrate along the tips of the arrowheads, as the cells were guided by the asymmetrical arrowhead tips which provided large contact areas. To the best of our knowledge, this is the first study demonstrating the use of thin TiOx arrowhead pattern in combination with a cell-repellent PDMS surface to provide guided cell migration unidirectionally without tall sidewall constraints. Additionally, high-resolution fluorescence imaging revealed that the asymmetrical distribution of focal adhesions, triggered by the patterned TiOx arrowheads with arm lengths of 10, 20, and 35 μm, promoted cell adhesion and protrusion along the arrowhead tip direction, resulting in unidirectional cell migration. These findings have important implications for the design of biointerfaces with ultrathin patterns to precisely control cell migration. Furthermore, microelectrodes were integrated with the patterned TiOx arrowheads to enable dynamic monitoring of cell migration using impedance measurement. This microfluidic device integrated with thin layer of guiding pattern and microelectrodes allows simultaneous control of directional cell migration and characterization of the cell movement of individual MC3T3-E1 cells, offering great potential for the development of biosensors for single-cell monitoring.

The editorial discusses the challenges and opportunities in modulating neural function, repairing damage, and integrating with neural signals through neural implants like brain-machine interfaces. It emphasizes the importance of biocompatibility and long-term stability in the nervous system. Various studies presented in the editorial explore topics such as the design of neurotrophic electrodes, retinal implants, electrode placement within the cortex, and the performance of neural implants in aged rats. These studies provide valuable insights into optimizing implant design for better performance, durability, and biocompatibility in clinical settings. [Extracted from the article]

An electrochemical investigation of 1,2- and 1,4-dihydroxybenzenes was carried out with platinum macro- and microelectrodes using square wave and cyclic voltammetry techniques. Furthermore, the effect of the two solvents—acetic acid and ethyl acetate—was compared. When using square wave voltammetry, signals only appeared at lower frequencies and only when the supporting electrolyte was in excess, as expected due to the relatively low permittivity of the used solvents. The behavior of hydroquinone and catechol did not differ significantly from that of their derivatives (dihydroxybenzaldehydes, dihydroxybenzoic acids and 2′,5′-dihydroxyacetophenone). When the cyclic voltammetric experiments using a microelectrode were extended to higher anodic potentials, electrode fouling was very significant in ethyl acetate after the potential region where steady-state oxidation to the corresponding quinone occurs. The substituent effect was not significant here either, which was proven by using different functional groups in different positions. In contrast, the position had a dramatic influence on the susceptibility to electropolymerization, as 1,2-dihydroxybenzenes—independent of the nature of the substituent on the benzene ring—deactivated the electrode, while 1,4-dihydroxybenzenes did not, possibly due to the different solubilities of the polymers formed from the primary oxidation product (quinones). A user-friendly analytical procedure is also proposed that uses an electropolymerization reaction and does not require frequent cleaning of the electrode via polishing, which is required usually especially with a microelectrode.

Ductile iron and copper coupons were aged 137–189 days and 2 days, respectively, with 2 mg Cl2 L−1 monochloramine under four water chemistries (pH 7 or 9 and 0 or 3 mg L−1 orthophosphate). Subsequently, microelectrode profiles of monochloramine concentration, oxygen concentration, and pH were measured from the bulk water to near the coupon reactive surface, allowing estimation of flux and apparent surface reaction rate constants for monochloramine and oxygen. Both metals showed similar trends with orthophosphate where orthophosphate decreased metal reactivity with monochloramine (pH 9) and oxygen (pH 7). Comparing iron and copper coupons, apparent surface reaction rate constants for monochloramine and oxygen were one and two orders of magnitude greater, respectively, for iron coupons under all conditions. Overall, this research provides the first insights into monochloramine concentration, oxygen concentration, and pH by direct measurement near ductile iron and copper reactive surfaces aged in the presence of monochloramine. [ABSTRACT FROM AUTHOR]

In the context of wound healing and tissue regeneration, precise control of cell migration direction is deemed crucial. To address this challenge, polydimethylsiloxane (PDMS) platforms with patterned 10 nm thick TiOx in arrowhead shape were designed and fabricated. Remarkably, without tall sidewall constraints, MC3T3-E1 cells seeded on these platforms were constrained to migrate along the tips of the arrowheads, as the cells were guided by the asymmetrical arrowhead tips which provided large contact areas. To the best of our knowledge, this is the first study demonstrating the use of thin TiOx arrowhead pattern in combination with a cell-repellent PDMS surface to provide guided cell migration unidirectionally without tall sidewall constraints. Additionally, high-resolution fluorescence imaging revealed that the asymmetrical distribution of focal adhesions, triggered by the patterned TiOx arrowheads with arm lengths of 10, 20, and 35 μm, promoted cell adhesion and protrusion along the arrowhead tip direction, resulting in unidirectional cell migration. These findings have important implications for the design of biointerfaces with ultrathin patterns to precisely control cell migration. Furthermore, microelectrodes were integrated with the patterned TiOx arrowheads to enable dynamic monitoring of cell migration using impedance measurement. This microfluidic device integrated with thin layer of guiding pattern and microelectrodes allows simultaneous control of directional cell migration and characterization of the cell movement of individual MC3T3-E1 cells, offering great potential for the development of biosensors for single-cell monitoring. [ABSTRACT FROM AUTHOR]

Flexible neural probes are attractive emerging technologies for brain recording because they can effectively record signals with minimal risk of brain damage. Reducing the electrode impedance of the probe before recording is a common practice of many researchers. However, studies investigating the impact of low impedance levels on high-quality recordings using flexible neural probes are lacking. In this study, we electrodeposited Pt onto a commercial flexible polyimide neural probe and investigated the relationship between the impedance level and the recording quality. The probe was inserted into the brains of anesthetized mice. The electrical signals of neurons in the brain, specifically the ventral posteromedial nucleus of the thalamus, were recorded at impedance levels of 50, 250, 500 and 1000 kΩ at 1 kHz. The study results demonstrated that as the impedance decreased, the quality of the signal recordings did not consistently improve. This suggests that extreme lowering of the impedance may not always be advantageous in the context of flexible neural probes. [ABSTRACT FROM AUTHOR]

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Macrophages are immune cells that play important roles in the human body's initial immune responses against pathogens and tumor cells. We investigated the use of electrical impedance monitoring to assess the differentiation of THP-1 monocyte into macrophages, which is necessary for immunotherapy research conducted. The change in resistance at 1 kHz and capacitance at 100 kHz measured were proportionally increased according to not only the increase in the density of resting macrophages differentiated by Phorbol-12-myristate-13-acetate treatment but also the initial number of THP-1 cells seeded on the electrode. Additionally, real-time impedance data from THP-1 cells after 48 h of cultivation demonstrated greater recognition of the resting macrophage phenotypes (adhesion cells) covered microelectrode surface with a significant increase of impedance signal in comparison with monocytes phenotypes (suspended cells). Furthermore, during the polarization phase of macrophages, the alternatively activated macrophage phenotype was larger and flatter than that of classically activated macrophage and resting macrophage phenotypes, indicating a correlation with a higher resistance and lower capacitance impedances at 1 kHz and 100 kHz of alternatively activated macrophages (4750 Ω and – 3.5 nF) than that of classically activated macrophages (2000 Ω and – 1.5 nF) and resting macrophages (3500 Ω and – 2.0 nF), respectively. The study's findings demonstrated that the impedance measurement system is high sensitivity and confidence in monitoring macrophages differentiation and polarization. The electrical impedance, which has significance for each macrophage phenotype, is compatible with macrophages characteristic features observed using flow cytometry and a microscope. [ABSTRACT FROM AUTHOR]

Neurochemicals, crucial for nervous system function, influence vital bodily processes and their fluctuations are linked to neurodegenerative diseases and mental health conditions. Monitoring these compounds is pivotal, yet the intricate nature of the central nervous system poses challenges. Researchers have devised methods, notably electrochemical sensing with micro-nanoscale electrodes, offering high-resolution monitoring despite low concentrations and rapid changes. Implantable sensors enable precise detection in brain tissues with minimal damage, while microdialysis-coupled platforms allow in vivo sampling and subsequent in vitro analysis, addressing the selectivity issues seen in other methods. While lacking temporal resolution, techniques like HPLC and CE complement electrochemical sensing's selectivity, particularly for structurally similar neurochemicals. This review covers essential neurochemicals and explores miniaturized electrochemical sensors for brain analysis, emphasizing microdialysis integration. It discusses the pros and cons of these techniques, forecasting electrochemical sensing's future in neuroscience research. Overall, this comprehensive review outlines the evolution, strengths, and potential applications of electrochemical sensing in the study of neurochemicals, offering insights into future advancements in the field. [ABSTRACT FROM AUTHOR]

Semi-transparent platinum electrodes were designed and optimized to implement photoluminescence (PL) and electrochemiluminescence (ECL) in microchannels under flow conditions. The luminescence properties of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)32+) were used to map steady-state emitted light through semi-transparent microchannel electrodes. Several diffusive-convective regimes were thus imposed in order to experimentally highlight the operating conditions of the electrodes, in particular the active zones at their upstream edges contributing to the Faradaic current. PL and ECL profiles were established on the electrode surfaces as a function of flow rate. The PL profiles confirmed the control of the process by mass transport. The data were validated by numerical simulations within the limits of experimental accuracy. ECL emission in presence of the co-reactant tri-n-propylamine (TPA) was also limited by mass transport. However, in comparison the characteristics of the ECL profiles demonstrated the complexity of the underlying mechanism involving Ru(bpy)32+ regeneration and TPA consumption.

This communication introduces a quick and easy method to modify a typical disk electrode's surface geometry. The method involves masking fragments of the flat surface of the working electrode, by applying a specific thin layer of chemically stable insulating material, leaving unvarnished, electrochemically active surface. Desired shapes are achieved by using a properly laser-engraved stainless-steel plate and a stamper to transfer the profiled varnish from the steel plate to the surface of the electrode. Three shapes - microdisk, microband, and ring electrodes - were applied to a platinum disk electrode, validated through optical and scanning electrochemical microscopies, and cyclic voltammetry. [ABSTRACT FROM AUTHOR]

Microelectrodes serve as a fundamental tool in electrophysiology research throughout the nervous system, providing a means of exploring neural function with a high resolution of neural firing information. We constructed a hybrid computational model using the finite element method and multicompartment cable models to explore factors that contribute to extracellular voltage waveforms that are produced by sensory pseudounipolar neurons, specifically smaller A-type neurons, and that are recorded by microelectrodes in dorsal root ganglia. The finite element method model included a dorsal root ganglion, surrounding tissues, and a planar microelectrode array. We built a multicompartment neuron model with multiple trajectories of the glomerular initial segment found in many A-type sensory neurons. Our model replicated both the somatic intracellular voltage profile of Ad lowthreshold mechanoreceptor neurons and the unique extracellular voltage waveform shapes that are observed in experimental settings. Results from this model indicated that tortuous glomerular initial segment geometries can introduce distinct multiphasic properties into a neuron's recorded waveform. Our model also demonstrated how recording location relative to specific microanatomical components of these neurons, and recording distance from these components, can contribute to additional changes in the multiphasic characteristics and peak-to-peak voltage amplitude of the waveform. This knowledge may provide context for research employing microelectrode recordings of pseudounipolar neurons in sensory ganglia, including functional mapping and closed-loop neuromodulation. Furthermore, our simulations gave insight into the neurophysiology of pseudounipolar neurons by demonstrating how the glomerular initial segment aids in increasing the resistance of the stem axon and mitigating rebounding somatic action potentials. [ABSTRACT FROM AUTHOR]

(1) Background: Intracortical microelectrodes (IMEs) are an important part of interfacing with the central nervous system (CNS) and recording neural signals. However, recording electrodes have shown a characteristic steady decline in recording performance owing to chronic neuroinflammation. The topography of implanted devices has been explored to mimic the nanoscale three-dimensional architecture of the extracellular matrix. Our previous work used histology to study the implant sites of non-recording probes and showed that a nanoscale topography at the probe surface mitigated the neuroinflammatory response compared to probes with smooth surfaces. Here, we hypothesized that the improvement in the neuroinflammatory response for probes with nanoscale surface topography would extend to improved recording performance. (2) Methods: A novel design modification was implemented on planar silicon-based neural probes by etching nanopatterned grooves (with a 500 nm pitch) into the probe shank. To assess the hypothesis, two groups of rats were implanted with either nanopatterned (n = 6) or smooth control (n = 6) probes, and their recording performance was evaluated over 4 weeks. Postmortem gene expression analysis was performed to compare the neuroinflammatory response from the two groups. (3) Results: Nanopatterned probes demonstrated an increased impedance and noise floor compared to controls. However, the recording performances of the nanopatterned and smooth probes were similar, with active electrode yields for control probes and nanopatterned probes being approximately 50% and 45%, respectively, by 4 weeks post-implantation. Gene expression analysis showed one gene, Sirt1, differentially expressed out of 152 in the panel. (4) Conclusions: this study provides a foundation for investigating novel nanoscale topographies on neural probes. [ABSTRACT FROM AUTHOR]

Simultaneous partial nitrification, anammox and denitrification (SNAD) is a sustainable and cost-effective technology for nitrogen removal from low-strength wastewater. However, knowledge of the biofilm microenvironment of the SNAD system is currently unsatisfactory. The purpose of this study was to evaluate organic carbon effects on the microenvironment and microbial growth in the SNAD biofilm system. Microelectrodes were used to investigate microbial activity in-depth within biofilms. ORP distribution of the SNAD system was positively related to anammox activity(R2 = 0.9), and had some influence on microbial community structure. The synergistic effect of anammox bacteria and denitrifiers could be achieved when the abundance ratio of anammox bacteria to denitrifying bacteria is greater than 1.2. [ABSTRACT FROM AUTHOR]

Current trends in neurobiological research focus on analyzing complex interactions within brain structures. To conduct relevant experiments, it is often essential to employ animals with unhampered mobility and utilize electrophysiological equipment capable of wirelessly transmitting data. In prior research, we introduced an open-source wireless electrophysiology system to surmount these challenges. Nonetheless, this prototype exhibited several limitations, such as a hefty weight for the wireless module, redundant system components, a diminished sampling rate, and limited battery longevity. In this study, we unveil an enhanced version of the open-source wireless electrophysiology system, tailored for in vivo monitoring of neural activity in rodent brains. This new system has been successfully tested in real-time recordings of in vivo neural activity. Consequently, our development offers researchers a cost-effective and proficient tool for studying complex brain functions. [ABSTRACT FROM AUTHOR]

Dopamine (DA), ascorbic acid (AA), and uric acid (UA) are crucial neurochemicals, and their abnormal levels are involved in various neurological disorders. While electrodes for their detection have been developed, achieving the sensitivity required for in vivo applications remains a challenge. In this study, we proposed a synthetic Au24Cd nanoenzyme (ACNE) that significantly enhanced the electrochemical performance of metal electrodes. ACNE-modified electrodes demonstrated a remarkable 10-fold reduction in impedance compared to silver microelectrodes. Furthermore, we validated their excellent electrocatalytic activity and sensitivity using five electrochemical detection methods, including cyclic voltammetry, differential pulse voltammetry, square-wave pulse voltammetry, normal pulse voltammetry, and linear scanning voltammetry. Importantly, the stability of gold microelectrodes (Au MEs) modified with ACNEs was significantly improved, exhibiting a 30-fold enhancement compared to Au MEs. This improved performance suggests that ACNE functionalization holds great promise for developing micro-biosensors with enhanced sensitivity and stability for detecting small molecules.

Neural interfacing devices interact with the central nervous system to alleviate functional deficits arising from disease or injury. This often entails the use of invasive microelectrode implants that elicit inflammatory responses from glial cells and leads to loss of device function. Previous work focused on improving implant biocompatibility by modifying electrode composition; here, we investigated the direct effects of electrical stimulation on glial cells at the electrode interface. A high-throughput in vitro system that assesses primary glial cell response to biphasic stimulation waveforms at 0 mA, 0.15 mA, and 1.5 mA was developed and optimized. Primary mixed glial cell cultures were generated from heterozygous CX3CR-1+/EGFP mice, electrically stimulated for 4 h/day over 3 days using 75 μm platinum-iridium microelectrodes, and biomarker immunofluorescence was measured. Electrodes were then imaged on a scanning electron microscope to assess sustained electrode damage. Fluorescence and electron microscopy analyses suggest varying degrees of localized responses for each biomarker assayed (Hoescht, EGFP, GFAP, and IL-1β), a result that expands on comparable in vivo models. This system allows for the comparison of a breadth of electrical stimulation parameters, and opens another avenue through which neural interfacing device developers can improve biocompatibility and longevity of electrodes in tissue.

Parkinson's Disease (PD) has historically been considered a disorder of motor dysfunction. However, a growing number of studies have demonstrated sensory abnormalities in PD across the modalities of proprioceptive, tactile, visual, auditory and temporal perception. A better understanding of these may inform future drug and neuromodulation therapy. We analysed these studies using a scoping review. In total, 101 studies comprising 2853 human participants (88 studies) and 125 animals (13 studies), published between 1982 and 2022, were included. These highlighted the importance of the basal ganglia in sensory perception across all modalities, with an additional role for the integration of multiple simultaneous sensation types. Numerous studies concluded that sensory abnormalities in PD result from increased noise in the basal ganglia and increased neuronal receptive field size. There is evidence that sensory changes in PD and impaired sensorimotor integration may contribute to motor abnormalities. [ABSTRACT FROM AUTHOR]

The ventricular papillary muscles (VPMs) can be a source of premature ventricular contractions (PVCs). Catheter ablation of VPM PVCs is challenging because of the anatomical complexity, such as the apical structures in proximity to the ventricular walls. The QDOT MICRO catheter (Biosense Webster, Diamond Bar, CA, USA) has microelectrodes embedded along the circumference of its distal tip and can provide information on which side of its tip myocardial activation is earlier. This repaired truncus arteriosus case demonstrates the usefulness of the microelectrode recording in identifying a PVC origin in a right VPM apex close to the right ventricular anterior wall. [ABSTRACT FROM AUTHOR]

Electrochemistry represents unique approaches for the promotion and mechanistic study of chemical reactions and has garnered increasing attention in different areas of chemistry. This expansion necessitates the enhancement of the traditional electrochemical cells that are intrinsically constrained by mass transport limitations. Herein, we present an approach for designing an electrochemical cell by limiting the reaction chamber to a thin layer of solution, comparable to the thickness of the diffusion layer. This thin layer electrode (TLE) provides a modular platform to bypass the constraints of traditional electrolysis cells and perform electrolysis reactions in the timescale of electroanalytical techniques. The utility of the TLE for electrosynthetic applications benchmarked using NHPI‐mediated electrochemical C−H functionalization. The application of microscale electrolysis for the study of drug metabolites was showcased by elucidating the oxidation pathways of the paracetamol drug. Moreover, hosting a microelectrode in the TLE, was shown to enable real‐time probing of the profiles of redox‐active components of these rapid electrosynthesis reactions. [ABSTRACT FROM AUTHOR]

Brain-Machine Interface systems (BMIs) are clinically valuable devices that can provide functional restoration for patients with spinal cord injury or improved integration for patients requiring prostheses. Intracortical microelectrodes can record neuronal action potentials at a resolution necessary for precisely controlling BMIs. However, intracortical microelectrodes have a demonstrated history of progressive decline in the recording performance with time, inhibiting their usefulness. One major contributor to decreased performance is the neuroinflammatory response to the implanted microelectrodes. The neuroinflammatory response can lead to neurodegeneration and the formation of a glial scar at the implant site. Historically, histological imaging of relatively few known cellular and protein markers has characterized the neuroinflammatory response to implanted microelectrode arrays. However, neuroinflammation requires many molecular players to coordinate the response - meaning traditional methods could result in an incomplete understanding. Taking advantage of recent advancements in tools to characterize the relative or absolute DNA/RNA expression levels, a few groups have begun to explore gene expression at the microelectrode-tissue interface. We have utilized a custom panel of ∼813 neuroinflammatory-specific genes developed with NanoString for bulk tissue analysis at the microelectrode-tissue interface. Our previous studies characterized the acute innate immune response to intracortical microelectrodes. Here we investigated the gene expression at the microelectrode-tissue interface in wild-type (WT) mice chronically implanted with nonfunctioning probes. We found 28 differentially expressed genes at chronic time points (4WK, 8WK, and 16WK), many in the complement and extracellular matrix system. Further, the expression levels were relatively stable over time. Genes identified here represent chronic molecular players at the microelectrode implant sites and potential therapeutic targets for the long-term integration of microelectrodes. Intracortical microelectrodes can record neuronal action potentials at a resolution necessary for the precise control of Brain-Machine Interface systems (BMIs). However, intracortical microelectrodes have a demonstrated history of progressive declines in the recording performance with time, inhibiting their usefulness. One major contributor to the decline in these devices is the neuroinflammatory response against the implanted microelectrodes. Historically, neuroinflammation to implanted microelectrode arrays has been characterized by histological imaging of relatively few known cellular and protein markers. Few studies have begun to develop a more in-depth understanding of the molecular pathways facilitating device-mediated neuroinflammation. Here, we are among the first to identify genetic pathways that could represent targets to improve the host response to intracortical microelectrodes, and ultimately device performance. [Display omitted] [ABSTRACT FROM AUTHOR]

Wearable health trackers for vital signs monitoring are becoming ever more important especially due to the global coronavirus pandemic (COVID-19) caused by the SARS‑CoV‑2 virus which severely affect the respiratory system and can cause cardiac manifestations. Particularly, wearable solutions which can seamlessly monitor heart activity are critical to facilitate personal preventive and remote healthcare, as well as to allow early diagnosis of cardiac dysfunctions. A fundamental enabler of wearable bioelectronics is the sensing bioelectrode which is used to record surface biopotentials. While a plethora of attempts have been reported to realize skin-conformal dry electrodes and electronic skin patches, oftentimes a very critical aspect of the electrode i.e., the actual electrical interfacing of the wearable electrode to readout circuits without disturbing the skin-electrode contact, is overlooked. To address this issue, this paper reports a unique tri-layer, polymer-metal-polymer skin-conformal microelectrode design with sidewall metal coating to achieve vertical interconnect accesses (VIAs) and realize contact pads for external interfacing. The novel and optimized process flow reported herein allows repeatable fabrication of flexible electrodes in arrayed format with yields exceeding 90%. Functionality of the microfabricated electrodes were demonstrated by successful acquisition of the electrocardiogram in lead-I configuration with clear detection of the P-QRS-T complex.