Ion Flux Measurements Research Articles

Microscopic Object Recognition and Localization Based on Multi-Feature Fusion for In-Situ Measurement In Vivo

Microscopic object recognition and analysis is very important in micromanipulation. Micromanipulation has been extensively used in many fields, e.g., micro-assembly operation, microsurgery, agriculture, and biological research. Conducting micro-object recognition in the in-situ measurement of tissue, e.g., in the ion flux measurement by moving an ion-selective microelectrode (ISME), is a complex problem. For living tissues growing at a rate, it remains a challenge to accurately recognize and locate an ISME to protect living tissues and to prevent an ISME from being damaged. Thus, we proposed a robust and fast recognition method based on local binary pattern (LBP) and Haar-like features fusion by training a cascade of classifiers using the gentle AdaBoost algorithm to recognize microscopic objects. Then, we could locate the electrode tip from the background with strong noise by using the Hough transform and edge extraction with an improved contour detection method. Finally, the method could be used to automatically and accurately calculate the relative distance between the two micro-objects in the microscopic image. The results show that the proposed method can achieve good performance in micro-object recognition with a recognition rate up to 99.14% and a tip recognition speed up to 14 frames/s at a resolution of 1360 × 1024. The max error of tip positioning is 6.10 μm, which meets the design requirements of the ISME system. Furthermore, this study provides an effective visual guidance method for micromanipulation, which can facilitate automated micromanipulation research.

Modified high frequency probe approach for diagnostics of highly reactive plasma

The paper introduces a modified approach of time resolved in situ diagnostics of highly reactive discharges (C2H2 in our case) usually used for a deposition process of various non-conductive thin films. Reactive plasma could create an insulating film onto inserted diagnostic tools, which distorts measured data and makes their processing unreliable; a typical problem of Langmuir probe measurements. The proposed approach utilizes a so-called radiofrequency (rf) Sobolewski probe for ion flux measurement which is further modified to also obtain the electron temperature in some cases and the ion density. In this work, we introduce the procedure where measured rf probe characteristics are transformed towards I–V curves of the plasma sheath with subtracted capacitive current. This processing enables not only the monitoring of plasma sheath impedance and the ion flux towards the substrate but also allows for an estimation of other parameters as the plasma density or electron temperature, respectively. We demonstrate that the substrate used for thin film deposition can act as an active probe itself. The relevance of the proposed method was verified in pure Ar discharge where the results correspond with conventional Langmuir probe diagnostics. Furthermore, internal plasma parameters of highly reactive Ar/C2H2 plasma, formed from acetylene, were evaluated, too.

Polymodal Mechanism for TWIK-Related K+ Channel Inhibition by Local Anesthetic.

Local anesthetics cause reversible block of pain and robustly inhibit TWIK-related K channel (TREK-1) currents. Before local anesthesia onset, injection of local anesthetics can cause unwanted transient pain. TREK-1 is an anesthetic-sensitive potassium channel that when inhibited produces pain. A disordered C-terminal loop of TREK-1 is thought to contribute to anesthetic sensitivity, but the molecular basis for TREK-1 inhibition by local anesthetics is unknown. Phospholipase D2 (PLD2) is an enzyme that produces phosphatidic acid (PA) required for TREK-1 activation and also binds to the channel's C terminus. Here, we use biophysical and cellular techniques to characterize direct and indirect lipid-mediated mechanism for TREK-1 inhibition (respectively). We characterized direct binding of local anesthetic to TREK-1 by reconstituting the purified channel into artificial membranes and measuring ion flux. We characterized indirect PA-mediated inhibition of TREK-1 by monitoring lipid production in live whole cells using a fluorescent PLD2 product release assay and ion channel current using live whole-cell patch-clamp electrophysiology. We monitored anesthetic-induced nanoscale translocation of PLD2 to TREK-1 channels with super-resolution direct stochastic reconstruction microscopy (dSTORM). We find local anesthetics tetracaine, lidocaine, and bupivacaine directly bind to and inhibit PLD2 enzymatic activity. The lack of PLD2 activity indirectly inhibited TREK-1 currents. Select local anesthetics also partially blocked the open pore of TREK-1 through direct binding. The amount of pore block was variable with tetracaine greater than bupivacaine and lidocaine exhibiting a minor effect. Local anesthetics also disrupt lipid rafts, a mechanism that would normally activate PLD2 were it not for their direct inhibition of enzyme catalysis. We propose a mechanism of TREK-1 inhibition comprised of (1) primarily indirect PLD2-dependent inhibition of lipid catalysis and (2) limited direct inhibition for select local anesthetics through partial open pore block. The inhibition through PLD2 explains how the C terminus can regulate the channel despite being devoid of structure and putative binding sites for local anesthetics.

Direct ion content measurements in a non-sputtering magnetron discharge

In present contribution we report the first direct measurements of ion fluxes in a non-sputtering magnetron discharge (NSMD) with Al cathode in Ar/O2 mixtures. The diagnostic unit comprising three-electrode electrostatic lens ion extractor, magnetic sector mass-analyzer, and a vacuum electron multiplier was calibrated and then used to record the time-resolved ion counts of Al+ and Ar+ both in NSMD and arc regimes. The results clearly indicate that in NSMD the dominant species are Ar ions while Al ion signal is lower than the sensitivity limit due to noise level, in contrast to the arc discharge. The capabilities of the diagnostics setup and its sensitivity limits are discussed.

Root vacuolar Na+ sequestration but not exclusion from uptake correlates with barley salt tolerance.

Soil salinity is a major constraint for the global agricultural production. For many decades, Na+ exclusion from uptake has been the key trait targeted in breeding programs; yet, no major breakthrough in creating salt-tolerant germplasm was achieved. In this work, we have combined the microelectrode ion flux estimation (MIFE) technique for non-invasive ion flux measurements with confocal fluorescence dye imaging technique to screen 45 accessions of barley to reveal the relative contribution of Na+ exclusion from the cytosol to the apoplast and its vacuolar sequestration in the root apex, for the overall salinity stress tolerance. We show that Na+ /H+ antiporter-mediated Na+ extrusion from the root plays a minor role in the overall salt tolerance in barley. At the same time, a strong and positive correlation was found between root vacuolar Na+ sequestration ability and the overall salt tolerance. The inability of salt-sensitive genotypes to sequester Na+ in root vacuoles was in contrast to significantly higher expression levels of both HvNHX1 tonoplast Na+ /H+ antiporters and HvVP1 H+ -pumps compared with tolerant genotypes. These data are interpreted as a failure of sensitive varieties to prevent Na+ back-leak into the cytosol and existence of a futile Na+ cycle at the tonoplast. Taken together, our results demonstrated that root vacuolar Na+ sequestration but not exclusion from uptake played the main role in barley salinity tolerance, and suggested that the focus of the breeding programs should be shifted from targeting genes mediating Na+ exclusion from uptake by roots to more efficient root vacuolar Na+ sequestration.

The S. cerevisiae cation translocation protein Trk1 is functional without its “long hydrophilic loop” but LHL regulates cation translocation activity and selectivity

In Saccharomyces cerevisiae, K+-uptake under K+-limiting conditions is largely mediated by the cation translocation systems Trk1 and Trk2 belonging to the family of SKT proteins. They are related to two-transmembrane-domain (inward rectifying K-) channels but unlike the symmetrical tetrameric structure of K-channels, a single Trk contains four pore-forming domains (A-D) encoded on one polypeptide chain. Between domains A and B Trks contain large cytosolic regions dubbed “long hydrophilic loop” (LHL). LHLs are not homologous/similar to any other identified protein (domain) and also show little similarity between Trk1 and Trk2. Here we demonstrate that Trk1 is functional without LHL. However, in growth experiments NaCl sensitivity of Trk1[ΔLHL] expressing cells is increased under K+-limiting conditions compared to full-length Trk1. Non-invasive ion flux measurements showed that K+-influx through Trk1 and Trk1[ΔLHL] is decreased in the presence of surplus Na+ due to permeability of the proteins for both cations and competition between them. Trk1[ΔLHL] is less affected than full-length Trk1 because it is more selective for K+ over Na+. Furthermore, K+ re-uptake after starvation is delayed and decreased in Trk1[ΔLHL]. Thus, a role of LHL is regulating cation fluxes through Trk1 by (i) allowing also Na+ to pass if monovalent cations (mainly K+) are limiting and (ii) by accelerating/enhancing a switch from low to high affinity ion translocation. We propose that LHL could modulate Trk1 transport properties via direct influence on a transmembrane helix (M2A) which can switch between bent and straight conformation, thereby directly modifying the radius of the pore and selectivity filter.

Multi-Channel System for Simultaneous <italic>In Situ</italic> Monitoring of Ion Flux and Membrane Potential in Plant Electrophysiology

Simultaneous detection of both ion flux and membrane potential in vivo and in situ in plants is a challenging research task. To explore the mechanisms of plant electrical activity, researchers urgently need to understand and determine the types of ions and the ion fluxes that pass in and out of cells during polarization and repolarization, but the required measurements are very difficult to perform. In this paper, we have developed a versatile system that can detect the ionic flux and the membrane potential, in vivo and in situ , simultaneously. The system uses a self-referencing ion-selective glass microelectrode and a membrane potential glass microelectrode as sensors. These sensors are linked through a preamplifier with high input impedance to a specific dynamic measurement system that can amplify small extracellular concentration gradient signals and realize simultaneous measurement of both the ion flux and the membrane potential. In addition, an interpolation fitting algorithm has been proposed to reduce the artifacts that are present in the in situ measurements during plant growth. The hydrogen ion fluxes in wheat roots were measured using the self-referencing ion-selective microelectrodes, and the proposed system was used to measure NaCl stimulation-induced changes in the membrane potentials and hydrogen ion fluxes of wheat root epidermal cells. The results demonstrate that the system can meet the ion flux and membrane potential measurement requirements.

Evidence of ion energy distribution shift in HiPIMS plasmas with positive pulse

The deposition of a dense and void-free coating in complex geometries can be obtained with High Power Impulse Magnetron Sputtering (HiPIMS) by negatively biasing the substrate. This accelerates the incoming metal ions that consequently densify the film. However, a biased substrate can be a technical challenge for large objects that are generally kept grounded. HiPIMS with a positive voltage pulse after the main negative one is a potential alternative to be still fully investigated. In this letter, we report on the first measurements of a dominant population of energetic ions in HiPIMS with a positive pulse. Time-integrated energy distribution functions of the background gas ions (Ar+) and target ions (Nb+) are measured with and without the positive pulse. The peak of low energy ions at ∼2 eV is shown to disappear by varying the duration of a +50 V pulse. For a sufficiently long duration of 100 μs, energy peaks in the range of ∼30 eV are observed for both Ar+ and Nb+. Negligible ion fluxes at the energies below 10 eV are measured for 250 μs, indicating an effective acceleration of ions towards the substrate. Time-resolved ion flux measurements provide insights on the positive pulse effect on the ion fluxes.

Direct measurement of lithium ion fluxes with a rotating ring disc electrode in potentiometric mode

Using potentiometric detection of lithium ions with a rotating ring disc electrode (RRDE), we report for the first time the simultaneous direct measurement of lithium ion fluxes for two experiments: a) O2 reduction in LiPF6 DMSO electrolyte and b) insertion and release of Li+ into and from LiMn2O4 spinel structure in contact with aqueous Li+ ion solution. The theory of potentiometric RRDE developed for local pH measurement (Albery, Calvo, 1983) could be applied to obtain quantitative description of lithium surface concentration which differs from the analytical concentration under current flow. The new potentiometric technique can detect mismatch of electron and lithium ion fluxes.

Energization of the Ring Current by Substorms.

The substorm process releases large amounts of energy into the magnetospheric system, although where the energy is transferred to and how it is partitioned remains an open question. In this study, we address whether the substorm process contributes a significant amount of energy to the ring current. The ring current is a highly variable region, and understanding the energization processes provides valuable insight into how substorm‐ring current coupling may contribute to the generation of storm conditions and provide a source of energy for wave driving. In order to quantify the energy input into the ring current during the substorm process, we analyze Radiation Belt Storm Probes Ion Composition Experiment and Helium Oxygen Proton Electron ion flux measurements for H+, O+, and He+. The energy content of the ring current is estimated and binned spatially for L and magnetic local time. The results are combined with an independently derived substorm event list to perform a statistical analysis of variations in the ring current energy content with substorm phase. We show that the ring current energy is significantly higher in the expansion phase compared to the growth phase, with the energy enhancement persisting into the substorm recovery phase. The characteristics of the energy enhancement suggest the injection of energized ions from the tail plasma sheet following substorm onset. The local time variations indicate a loss of energetic H+ ions in the afternoon sector, likely due to wave‐particle interactions. Overall, we find that the average energy input into the ring current is ∼9% of the previously reported energy released during substorms.

MMS Observations of Harmonic Electromagnetic Ion Cyclotron Waves

AbstractHarmonically related electromagnetic ion cyclotron waves with the fundamental frequency near the double oxygen cyclotron frequency were observed by the MMS spacecraft on 18–20 May 2016. The wave activity lasted for three days, detected by the spacecraft on their consecutive inbound passages through the Earth's plasma sheet boundary layer. The waves were seen in both magnetic and electric fields, formed by over 10 higher order harmonics. Simultaneous ion flux measurements show the presence of ion ring distributions suggesting the energy source for the observed waves. The ion cyclotron harmonics were observed together with broadband waves extending from ~Hz to ~kHz frequency range, ion and electron phase space holes, and chorus waves. During some intervals, there is a clear modulation of chorus wave packets at the ion cyclotron fundamental harmonic frequency. These observations are particularly interesting since they suggest cross‐frequency and cross‐species coupling between processes happening on ion and electron scales.

A Sodium Transporter HvHKT1;1 Confers Salt Tolerance in Barley via Regulating Tissue and Cell Ion Homeostasis.

Our previous studies showed that high salt tolerance in Tibetan wild barley accessions was associated with HvHKT1;1, a member of the high-affinity potassium transporter family. However, molecular mechanisms of HvHKT1;1 for salt tolerance and its roles in K+/Na+ homeostasis remain to be elucidated. Functional characterization of HvHKT1;1 was conducted in the present study. NaCl-induced transcripts of HvHKT1;1 were significantly higher in the roots of Tibetan wild barley XZ16 relative to other genotypes, being closely associated with its higher biomass and lower tissue Na+ content under salt stress. Heterologous expression of HvHKT1;1 in Saccharomyces cerevisiae (yeast) and Xenopus laevis oocytes showed that HvHKT1;1 had higher selectivity for Na+ over K+ and other monovalent cations. HvHKT1;1 was found to be localized at the cell plasma membrane of root stele and epidermis. Knock-down of HvHKT1;1 in barley led to higher Na+ accumulation in both roots and leaves, while overexpression of HvHKT1;1 in salt-sensitive Arabidopsis hkt1-4 and sos1-12 loss-of-function lines resulted in significantly less shoot and root Na+ accumulation. Additionally, microelectrode ion flux measurements and root elongation assay revealed that the transgenic Arabidopsis plants exhibited a remarkable capacity for regulation of Na+, K+, Ca2+ and H+ homeostasis under salt stress. These results indicate that HvHKT1;1 is critical in radial root Na+ transport, which eventually reduces shoot Na+ accumulation. Additionally, HvHKT1;1 may be indirectly involved in retention of K+ and Ca2+ in root cells, which also improves plant salt tolerance.

Analysis of retarding field energy analyzer transmission by simulation of ion trajectories

Retarding field energy analyzers (RFEAs) are used routinely for the measurement of ion energy distribution functions. By contrast, their ability to measure ion flux densities has been considered unreliable because of lack of knowledge about the effective transmission of the RFEA grids. In this work, we simulate the ion trajectories through a three-gridded RFEA using the simulation software SIMION. Using idealized test cases, it is shown that at high ion energy (i.e., >100 eV) the transmission is equal to the optical transmission rather than the product of the individual grid transparencies. Below 20 eV, ion trajectories are strongly influenced by the electric fields in between the grids. In this region, grid alignment and ion focusing effects contribute to fluctuations in transmission with ion energy. Subsequently the model has been used to simulate the transmission and energy resolution of an experimental RFEA probe. Grid misalignments reduce the transmission fluctuations at low energy. The model predicts the minimum energy resolution, which has been confirmed experimentally by irradiating the probe with a beam of ions with a small energy bandwidth.

Nitrate and ammonium uptake in 21 common species of moss from Vancouver Island, British Columbia

Mosses play key ecological roles in water and nutrient retention in many ecosystems, yet relatively little is known of the functional characteristics of moss species, particularly nutritional characteristics. We investigated the net flux of ammonium, nitrate, and protons, using a microelectrode ion flux measurement system, in the gametophytes of 21 common species of moss from three contrasting locations in southern coastal British Columbia. The general location from which mosses were collected did not significantly affect ammonium or nitrate uptake. Proton efflux was greatest in mosses from locations with high rainfall. Rates of nitrate uptake differed among moss families, but there were no significant differences in uptake among species within families. Ammonium net flux differed among moss families, but also among species nested within family, with some species showing uptake and other showing ammonium efflux. In general, moss species native to dry habitats appeared to have higher rates of nitrogen uptake when ammonium and nitrate were available under favourable conditions.

The Flow Cytometric Osmotic Fragility Test Is an Effective Screening Method for Dehydrated Hereditary Stomatocytosis

Introduction: Dehydrated hereditary stomatocytosis (DHSt) or hereditary xerocytosis (HX) is a form of congenital hemolytic anemia characterized by red blood cell (RBC) dehydration. Heterozygous mutations in PIEZO1, a mechanically-activated ion channel, cause DHSt. Recently, KCNN4, which encodes the Gardos channel, has been found to be the second pathogenic gene for DHSt. DHSt is characterized by an alteration in the RBC morphology in target cells, stomatocytes, and/or echinocytes, and RBC deformability assessments by ektacytometry as well as RBC ion flux measurements are currently the standard laboratory tests for DHSt, but their use in laboratories is limited. The flow cytometric osmotic fragility (FCM-OF) test is a useful diagnostic test for hereditary spherocytosis (HS) and also for hereditary elliptocytosis (HE). In this study, we showed that the FCM-OF test could also successfully diagnose DHSt.Subjects: A total of 46 cases of RBC membrane disorders were examined, and tentative diagnoses were made based on the RBC morphology, acid glycerol lysis time, and eosin 5'-maleimide binding tests, resulting in HS (n=31), HE (n=6), and DHSt (n=9).Methods: The number of RBCs in isotonic and hypotonic buffers were measured by flow cytometry. The degree of osmotic fragility was expressed as the “percentage residual RBCs (%RRC)”. We confirmed the DHSt diagnosis by the massively paralleled sequencing using our custom panels targeting 68 hemolytic anemia-related genes with the next-generation sequencer.Results: Both HS and HE patients showed a decrease in %RRC; HS (18.0±8.9%, p<0.001) and HE (41.8±15.7%, p<0.001) compared to normal control (66.7±1.5%). DHSt patients showed a significant increase (112.6±34.5%, p<0.001) in FCM-OF. Additionally, next-generation sequencing revealed consistent causative gene mutations for DHSt; PIEZO1 (p.R2488Q and p.E2496ELE) or KCNN4 (p.P204R, p.A279T and p.R352H).Discussion: We examined 77 patients with congenital hemolytic anemia recently, and 59 cases were confirmed by diagnostic tests (76.6%). The results were as follows: 48 cases of RBC membrane abnormality (62.3%), 6 cases of RBC enzymopathy (7.8%), and 5 cases of hemoglobinopathy (6.5%). Of the cases of RBC membrane disorders, 31 cases of HS, 9 cases of DHSt, and 8 cases of HE were identified. These observations suggest that DHSt is the second-most common RBC membranopathy in Japan, and that the FCM-OF test and targeted sequencing efficiently discriminate DHSt from other RBC membrane disorders. DisclosuresNo relevant conflicts of interest to declare.

Voltammetric simultaneous ion flux measurements platform for Cu2+, Pb2+ and Hg2+ near rice root surface: Utilizing carbon nitride heterojunction film modified carbon fiber microelectrode

Developing an available analysis platform for simultaneous heavy metal ion flux measurement at trace level is urgent for understanding the mechanisms of phytoremediation. Herein, oxygenous functionalized carbon nitride nanosheets assembled porous films on multi-walled carbon nanotube formed nano frameworks was firstly prepared on a carbon fiber disk microelectrode by an advanced drop-casting method. The as-prepared electrode shows low detection limit (The 1.0×10−13molL−1 for Cu2+, 1.8×10−11molL−1 for Pb2+ and 8.0×10−12molL−1 for Hg2+), acceptable linear range (6.6×10−12∼8.5×10−6molL−1 for Cu2+, 8.1×10−10∼8.5×10−6molL−1 for Pb2+ and 2.2×10−11∼8.5×10−6molL−1 for Hg2+) and fine selectivity in simultaneous determination. The improved accumulation ability of modifier is attributed to improved conductivity and the porous morphology of the film, which may improve useful rate of the chelation groups. Based on the as-prepared electrode and a stepper motor, the voltammetric platform for simultaneous heavy metal ion flux measurement at trace level is fabricated for the first time. This platform can be utilized for mechanism investigation of simultaneous metal uptake on the surface of rice roots at trace level.

Quantifying inorganic nitrogen uptake capacity among ectomycorrhizal fungal species using MIFE microelectrode ion flux measurements: theory and applications

A growing appreciation of the intimate association between trees and a wide diversity of mycorrhizal fungi in forest ecosystems is leading to the view that trees and their associated mycorrhizal symbionts should be considered meta-organisms or holobionts. For ectomycorrhizal associations, nitrogen (N) mobilization and uptake is a major contribution from the fungal partners. This paper reviews the traditional methods of measuring N uptake by ectomycorrhizae, and describes the application of microelectrode ion flux measurement of nitrogen uptake using the MIFETM technique to ectomycorrhizal fungi associated with forest trees. From results obtained with microelectrode ion flux measurement thus far, we argue that plant N uptake capacity should be considered an exogenous trait, related to the functional diversity among ectomycorrhizal species and communities, rather than a function of host plant root physiology, alone.

Root potassium and hydrogen flux rates as potential indicators of plant response to zinc, copper and nickel stress

The practice of phytoremediation often requires that the plants used be exposed to a combined stress of multiple heavy metals. While the uptake and translocation abilities of roots is of primary importance, the direct effect of elevated concentrations of multiple heavy metals on the root physiology, including ion fluxes, is not often measured or compared between species in these studies.Four plant species (poplar, willow, hemp and alfalfa) that were selected for a long-term phytoremediation project were grown hydroponically in the presence and absence of a combined heavy metal stress (zinc, copper and nickel), resembling field conditions. Short- and long-term root potassium and hydrogen flux rates were measured with non-invasive ion selective electrodes. Anatomical observations of root and shoot tissues, as well as accumulations of heavy metals were made with transmission electron microscopy. Biomass, gas exchange parameters and pigment concentrations were all evaluated to assess whole-plant effects of the heavy metal treatment.Differences in the short-term induction of increased K+ efflux and decreased H+ influx from the roots among the four species were reflective of the long-term declines in photosynthetic capacity and growth observed in poplar and willow, but not in hemp. Tissue degradation patterns and increased K+ efflux in poplar, willow and alfalfa due to heavy metal stress are consistent with reports in the literature of an imbalance in ROS and efficient scavenging of hydroxyl radicals. Taken together, results indicate that ion flux measurements can predict heavy metal stress sensitivity and support their potential use for describing root-level responses to the combined contaminant conditions often observed in sites selected for phytoremediation.

Multi-electrode system for measurement of transmembrane ion-fluxes through living epithelial cells

Cystic Fibrosis (CF) is the most common fatal human genetic disease. It is caused by the defect in a single anion channel protein which affects ion and water transport across the epithelial tissue. A flat multi-electrode platform of diameter 12mm, allowing for measurement of four ions: sodium, potassium, hydrogen and chloride by exchangeable/replaceable ion-selective electrodes is described. The measurement is possible owing to the architecture of the platform which accommodates all the electrodes and inlets/outlets. The platform fits to the cup and operates in a small volume of the solution bathing the living epithelial cell layer (membrane) deposited on a porous support of the cup, which allows for effective monitoring of ion concentration changes. By applying two multi-electrode platforms, it is possible to measure the ion transmembrane fluxes. The inlet and outlet tubes in the platforms allow for on-fly change of the calibrants, ion-concentration changes and ion channel blockers. Using different ion-concentration gradients and blockers of ion-transporting molecules we show for the first time that sodium ions flow from the basolateral to apical face of the cell monolayer via a paracellular route and return also via a transcellular one, while chloride anions are transported back and forth exclusively via a transcellular route.

Solid Contact Ion-Selective Electrodes for in Situ Measurements at High Pressure.

Solid contact polymeric ion-selective electrodes (SC-ISEs) have been fabricated using microporous carbon (μPC) as the ion-to-electron transducer, loaded with a liquid membrane cocktail containing both ionophore and additive dissolved in plasticizer. These SC-ISEs were characterized and shown to be suitable for analysis in aqueous environments at pressures of 100 bar. Potassium ISEs, prepared in this manner, showed excellent performance at both atmospheric and elevated pressures, as evaluated by their response slopes and potential stability. These novel SC-ISEs were shown to be capable of measuring K+ at pressures under which traditional liquid-filled ISEs fail. Furthermore, the effect of pressure on the response of these sensors had little or no effect on potential, sensitivity, or limit of detection. High pressure sensor calibrations were performed in standard solutions as well as simulated seawater samples to demonstrate their usefulness as sensors in a deep-sea environment. These novel SC-ISE sensors show promise of providing the ability to make in situ real-time measurements of ion-fluxes near deep-ocean geothermal vents.