Free Sodium Ions Research Articles

Sodiophilic Substrate Induces NaF-Rich Solid Electrolyte Interface for Dendrite-Free Sodium Metal Anode.

3D substrate with abundant sodiophilic active sites holds promise for implementing dendrite-free sodium metal anodes and high-performance sodium batteries. However, the heightened electrode/electrolyte side reactions stemming from high specific surface area still hinder electrode structure stability and cycling reversibility, particularly under high current densities. Herein, the solid electrolyte interface (SEI) component is regulated and detrimental side reactions are restrained through the uniform loading of Na-Sn alloy onto a porous 3D nanofiber framework (NaSn-PCNF). The strong interaction between Na-Sn alloy and PF6 - anions facilitates the dissociation of sodium salts and releases more free sodium ions for effective charge transfer. Simultaneously, the modulations of the interfacial electrolyte solvation structure and the construction of a high NaF content SEI layer stabilize the electrode/electrolyte interface. NaSn-PCNF symmetrical battery demonstrates stable cycling for over 600 h with an ultralow overpotential of 24.5mV under harsh condition of 10 mA cm-2 and 10 mAh cm-2. Moreover, the full cells and pouch cells exhibit accelerated reaction kinetics and splendid capacity retention, providing valuable insights into the development of advanced Na substrates for high-energy sodium metal batteries.

Efflorescence mitigation in fly ash/slag-based geopolymers: The role of precursor composition and proportions, and admixtures

This study explores enhancing geopolymer mechanical robustness and reducing efflorescence by adjusting precursor compositions and ratios, complemented by incorporating select admixtures. The integration of slag facilitates the geopolymerization process while concurrently diminishing the sodium ion leaching concentration, contributing to a reduction in efflorescence manifestations. The employment of metakaolin is further identified as a significant factor in the substantial decrease of free sodium ions, thereby curtailing efflorescence. While polycarboxylate and carboxymethyl cellulose exhibit differential impacts on the structural strength, their excessive application may exacerbate efflorescence. Notably, sodium polyacrylate is highlighted for its proficiency in markedly diminishing water permeability and virtually eradicating efflorescence through establishing a compact network that impedes the mobility of water and sodium ions, thereby forestalling their surficial migration.

Degradation of GFRP bars in alkaline environments: An experimental and molecular dynamics study

Glass fibre reinforced polymer (GFRP) bars are widely used as a replacement for reinforced bars due to their high strength-to-weight ratio, whereas they also show a high safety risk for corrosion potential from alkaline ions attack in concrete. In this study, the mechanical property evolution and degradation mechanism of GFRP bars in alkaline environments was studied by using experimental and molecular dynamics simulations. The results show that the decreased strength of the GFRP was mainly associated with the increase in the hydroxide concentration (COH-) in the corrosive solution rather than other ions. The tensile strength of the GFRP bars declined by approximately 10% after 300 days of exposure when the pH of the corrosion solution approached 13. When the pH barely reached 10, the resin-fibre interlaminar shear strength slumped by approximately 29%. The favorable hydrogen bonding network was disrupted by alkaline ions, resulting in a lower interaction energy between water molecules and epoxy resin chain segments. In addition, OH− was distributed around the ester bond and attacked the ester group, and finally, the ester bond was hydrolysed to form carboxylate and alcohol. Free sodium ions combine rapidly with oxygen lone electrons (Na-Ow), thereby accelerating water-resin debonding aging by breaking hydrogen bonds within the polymer network. The hydroxyl radicals further invade the fibres through the microcracks formed inside the resin, causing localized etching of the fibres. The study will provide a theoretical basis for the design of anti-corrosion modification of GFRP bars.

Ionic conductive and stretchable interpenetrating hydrogels prepared with homogenously synthesized acrylamide-modified agar and polyacrylamide for strain sensing

In this article, the IPN hydrogels were prepared with acrylamide-modified agar (AMA), oxidized alginate (ADA) and polyacrylamide (PAM). The agar was firstly homogenously modified with acrylamide to facilitate the formation of hydrogen bonds and enhancement of the ionic conductivity of the hydrogel. The prepared IPN hydrogels showed high flexibility and conductivity. The composite hydrogel prepared with 20 wt% acrylamide, 0.25 wt% AMA and 5% ADA (hydrogel-5) possessed high toughness and can be stretched 20 times of its origin length. The hydrogel-5 also showed highest elastic modulus of 110 kPa compared with other hydrogels. The free potassium and sodium ions in acrylamide-modified agar and oxidized alginate chains endowed the hydrogel with conductive properties. The IPN hydrogels showed strain sensitive properties and can be used to detect various motion of human beings. The hydrogel still possessed high flexibility and conductivity after storing for six months. The IPN hydrogels with conductivity and high mechanical properties can be applied in various engineering fields.

Ultra-Stable, Ultra-Long-Lifespan and Ultra-High-Rate Na-ion Batteries Using Small-Molecule Organic Cathodes

Molecule-aggregation organic electrodes in principle possess the “single-molecule-energy-storage” capability for metal-ion rechargeable batteries. Besides dissolution issue, the effect of possible solvent co-intercalation in liquid electrolytes also devalues the true performance of organic electrodes due to the weak Van der Waals forces among organic molecules. Herein, a small-molecule organic cathode called [N,N’-bis(2-anthraquinone)]-perylene-3,4,9,10-tetracarboxydiimide (PTCDI-DAQ, 200 mAh g−1) can deliver the unprecedented results in sodium-ion batteries (SIBs) by carefully choosing high-concentration electrolytes, which can offer more free sodium ions and decrease the solvent co-intercalation effect. Consequently, PTCDI-DAQ can deliver an ultra-stable capacity above 153 mAh g−1 during a long-lifetime operation test in half cells (10 months at least). In full cells, the resulting PTCDI-DAQ II Na3Bi SIBs can deliver a peak discharge capacity of 206 mAh g−1cathode with an average voltage of 1.2 V, running with no capacity decay over 4 months. Meanwhile, our PTCDI-DAQ II Na3Bi SIBs can re-store a world record of 70% capacity retention (142 mAh g−1cathode) at 20 A g−1cathode (100 C). To the best of our knowledge, PTCDI-DAQ can currently represent the best organic cathode for SIBs in the world; and the integrated performance of our PTCDI-DAQ II Na3Bi SIBs can compete with the best SIBs reported to date.

Ultra-Stable, Ultra-Long-Lifespan and Ultra-High-Rate Na-Ion Batteries Using Small-Molecule Organic Cathodes

Molecule-aggregation organic electrodes in principle possess the “single-molecule-energy-storage” capability for metal-ion rechargeable batteries. Besides dissolution issue, the effect of possible solvent co-intercalation in liquid electrolytes also devalues the true performance of organic electrodes due to the weak Van der Waals forces among organic molecules. Herein, a small-molecule organic cathode called [N,N’-bis(2-anthraquinone)]-perylene-3,4,9,10-tetracarboxydiimide (PTCDI-DAQ, 200 mAh g-1) can deliver the unprecedented results in sodium-ion batteries (SIBs) by carefully choosing high-concentration electrolytes, which can offer more free sodium ions and decrease the solvent co-intercalation effect. Consequently, PTCDI-DAQ can deliver an ultra-stable capacity above 173 mAh g-1 during a long-lifetime operation test in half cells (6 months at least). In full cells, the resulting PTCDI-DAQ II Na3Bi SIBs can deliver a peak discharge capacity of 206 mAh g-1cathode with an average voltage of 1.2 V, running with no capacity decay over 4 months. Meanwhile, our PTCDI-DAQ II Na3Bi SIBs can re-store a world record of 70% capacity retention (142 mAh g-1cathode) at 20 A g-1cathode (100 C). To the best of our knowledge, PTCDI-DAQ can currently represent the best organic cathode for SIBs in the world; and the integrated performance of our PTCDI-DAQ II Na3Bi SIBs can compete with the best SIBs reported to date.small-molecule organic cathodes; ultra-stability; long lifespan; high rate; Na-ion batteries

Flow Cytometric Monitoring of Dynamic Cytosolic Calcium, Sodium, and Potassium Fluxes Following Platelet Activation.

The interaction of platelet agonists with their respective membrane receptors triggers intracellular signaling, among which cytosolic ion fluxes play an important role in activation processes. While the key contribution of intercellular free calcium is accepted, sodium and potassium roles in platelet activation have been less investigated in recent studies. Here, we implemented a novel flow-cytometric method to monitor over time cytosolic free calcium, sodium, and potassium ion fluxes upon platelet activation and we demonstrate the feasibility of real-time visualization of ion kinetics, in particular with a focus on sodium and potassium. Platelets were loaded with selective ion indicators, Fluo-3 (Ca2+ ), ION NaTRIUM Green-2 (Na+ ), and ION Potassium Green-2 (K+ ). Fluorescence was monitored by flow cytometry. After measurement of a stable baseline, platelets were activated and ion indicator fluorescence was acquired over time, up to 10 min. Platelets were activated with either thromboxane analogue U46619, ADP, thrombin, TRAP6 (PAR-1 agonist), AYPGKF (PAR-4 agonist), convulxin (collagen receptor GPVI agonist), or combinations thereof. We evaluated preanalytical parameters (in particular dye loading time and concentration) to implement an accurate method. Subsequently, we characterized cytosolic calcium, sodium, and potassium kinetics in response to platelet agonists. We observed different patterns of agonist synergism. In conclusion, the present work highlights the use of cytosolic ion monitoring by flow cytometry to investigate characteristic calcium, sodium, and potassium mobilization patterns following platelet activation. This easy technique opens a new way to analyze signaling in different platelet subpopulations and it should prove useful for investigating platelet pathophysiology. © 2020 International Society for Advancement of Cytometry.

Carbon dioxide adsorption on a modified zeolite with sodium dodecyl sulfate surfactants: A molecular dynamics study

Molecular dynamics simulations are carried out to study adsorption of Carbon dioxide (CO2) in a zeolite modified with anionic surfactants at different gas concentrations. Sodium dodecyl sulfate (SDS) surfactant is used and simulations at different SDS concentrations were conducted. The results show that adsorption of the gas is influenced by the amount of SDS on the zeolite surface. In addition, gas retention inside and outside the solid is observed and it strongly depends on the free sodium ions in the zeolite. The most favorable adsorption takes place at low CO2 concentrations with few SDS molecules. Adsorption was studied in terms of density profiles and pair correlation functions and strong interactions of the CO2 molecules with the sodium ions were observed.

A method for multiparametric statistical quantification of the heterogeneity of free Na+ concentration by 19F MR spectroscopy: Proof of principle in silico and in vitro

Sodium(I) (Na+ ) is one of the most important cations in mammalian tissues. Since Na+ plays a key role in basic cell function, noninvasive methods for measuring intracellular concentrations of free sodium ions in biological tissue have been developed on the basis of 19 F NMR spectroscopy. However, intracellular Na+ levels are often not uniform throughout a tissue volume (or voxel) being measured. In such cases, [Na+ ] heterogeneity is not reflected in results obtained by the classical technique, and may even result in biased average values. For this reason, we have designed an approach for quantifying [Na+ ] heterogeneity. First, the 19 F MRS resonance from FCrown-1 serving as a "Na+ probe" is transformed into a [Na+ ] curve. Then the digital points of the resulting [Na+ ] profile are used to construct a histogram with specially developed algorithms. From each [Na+ ] histogram, at least eight quantitative parameters describing the underlying statistical [Na+ ] distribution were computed: weighted median, weighted mean, standard deviation, range, mode(s), kurtosis, skewness, and entropy. In addition to our new paradigm, we present a first validation based on (i) computer simulations and (ii) experimentally obtained 19 F MR spectra of model solutions. This basic proof of principle warrants future in vivo experiments, in particular because of its ability to provide quantitative information complementary to that made available by commonly used 23 Na MRI: (i) multiparametric statistical characterization of [Na+ ] distributions; (ii) total [Na+ ] heterogeneity analysis not intrinsically limited by the size of any MRI voxels; and (iii) analysis of unequivocally intracellular [Na+ ], as opposed to measurement of a combination of intra- and extracellular [Na+ ].

D.C. conductivity behaviour of poly(vinyl alcohol)-based ferrogels: role of borax and carbonyl iron

The d.c. conductivity of poly(vinyl alcohol) hydrogels and ferrogels, cross-linked with borax, has been studied using two-probe resistance measurement method as a function of cross-linker and dopant concentrations. The availability of charge carriers (i.e. unbound borate ions and free sodium ions) in these matrices is seen to vary with cross-linker and dopant concentrations. Increase in borax concentration leads to the rise in d.c. conductivity values. Enhancement in the carbonyl iron dopant proportions, at unchanged borax concentrations, causes a decrease in the conductivity. This behaviour is explained on the basis of structural modifications introduced within the network matrix owing to the variations in cross-linker and dopant concentrations.

Dielectric relaxation spectroscopy of aqueous micellar electrolyte solutions: A novel application to infer Dukhin number and zeta potential of a micelle.

The complex permittivities of aqueous SDS solutions, with and without the addition of sodium chloride (NaCl), are measured in the frequency range from 200 MHz to 14 GHz. The SDS concentrations are chosen such that the SDS molecules aggregate to micelles. In this frequency range, the measured spectra allow for the identification of two different relaxation processes. That is, the relaxation of the water molecules at frequencies above 1 GHz and the micellar relaxation at frequencies lower than 1 GHz. It is found that the addition of NaCl to the system mostly affects the micellar relaxation process. In detail, the time constant as well as the amplitude of the relaxation decrease by adding NaCl. These effects are attributed to the change in the solution conductivity that changes the properties of the micelle's electrical double layer. We also extract the Dukhin number of the micelles as a function of surfactant and electrolyte content from the measurements. The Dukhin number is a dimensionless group that describes the influence of the surface conductivity on a phenomena. A regression between Dukhin numbers and free sodium ions is found so that all data collapses on a single curve independent of the surfactant concentration. The surface conductivity is a manifestation of the electrical double layer and we use the Bikerman equation to infer the zeta potential of the micelles. Comparison to literature data shows very good agreement and proves that dielectric relaxation spectroscopy can be engaged to infer the zeta potential of micelles. Abbreviations: CMC critical micelle concentration, DRS dielectric relaxation spectroscopy, EDL electrical double layer.

In Situ Metal Electroplating for High Energy Anode Free Sodium Battery

The major advantage of sodium-ion batteries (SIBs) over lithium-ion is the lower cost of materials (Na vs Li and Al current collector replacing Cu); while the biggest drawback is the lower energy density (due to larger ionic radius and lower redox potential of Na+). Considering the most common grid-scale energy storage Li-ion system: LiFePO4 – Graphite (120 Wh/kg), simple replacement of Li and Cu with Na and Al, respectively, would results in only about 15% cost reduction. This means that Na-ion batteries need to have energy density higher than 102 Wh/kg in order to be competitive with LFP systems, which is hardly achievable in full cells comprising oxide-based cathodes and carbon anodes. Therefore, to commercialise SIBs for stationary energy storage, novel concept batteries with higher energy densities and considerably lower production costs need to be designed and developed. The concept of fabricating batteries in the discharged state with only an appropriate current collector (anode free) is an elegant method to achieve these aims. On the initial charge, reactive metal (Li or Na) is electroplated at the current collector, and so, during electrochemical cycling, the cell operates as a battery which contains only the amount of metal that is supplied by the positive electrode. Since Na metal has very high specific capacity (1166 mAh/g), the lowest possible working potential for SIBs and there is no anode material, the achievable energy density is extremely high. Nevertheless, in order to realise such systems we have to overcome several obstacles such as dendritic growth, nucleation potential, homogeneous plating as well as large volume changes. In this work we investigated anode free SIBs with particular focus on the battery’s components. We compared performance of several different current collectors and electrolytes. We also considered various cathode materials including conventional layered oxides or Prussian blue analogues. These materials differ in sodium storage mechanisms, working potentials and specific capacities as well as manufacturing costs. For instance, our tests of Na0.90Fe[Fe(CN)6] cathode and carbon coated Al current collector showed outstanding capacity of ~120 mAh/g over 250 cycles (Fig. 1). The average discharge potential is 3.2 V, which results in remarkable energy density of 384 Wh/kg. This is only slightly lower than the energy density of LiMn2O4 (410–492 Wh/kg) or LiFePO4 (518–587 Wh/kg). However, Li-ion values are based only on active mass of oxide cathode and in full cell configurations the graphite anode would have to be taken into account. This is not the case for anode free SIBs and therefore the energy density is already much higher than state-of-the-art LIBs. The system showed also remarkable rate capabilities up to 20C discharge rate, resulting in power density reaching 11 kW/kg. Moreover, the utilisation of inexpensive Prussian Blue analogues instead of transition metal oxides would contribute to lowering the cost even further. In conclusion, electroplating anode free sodium ion batteries can overtake LIBs in both performance and economic factors, emerging as one of the most promising and viable technologies for medium to large scale energy storage applications. Figure 1

Bottom–up assembly of strongly–coupled Na3V2(PO4)3/C into hierarchically porous hollow nanospheres for high–rate and –stable Na–ion storage

Herein, a three–dimensional (3D) Na3V2(PO4)3–based hollow nanosphere with hierarchical pores (3DHP–NVP@C) has been firstly reported. Detailed studies reveal that this novel architecture is made up from the bottom–up assembly of carbon–coating NVP nanoparticles. The hierarchically porous structure offers ample space for the intimate contact between electrode/electrolyte and eliminates the disadvantageous reducing of effective surface areas in manufacturing the electrodes, as well as stabilizes the structure upon repeated sodium ions insertion/extraction, resulting to the barrier–free sodium ion diffusions and long–term cycling life. On the other hand, the graphitic carbon shells construct into a highly–conductive framework that can ensure the ultrafast electrons transfer. Consequently, extraordinary high–rate and ultralong–cycle capabilities that are superior to any other NVP–based material are obtained: the outstanding high–rate capacity retention (over 80% of the 1C capacity is retained at 400C), ultralong life span (90.9% and 92.5% capacity retention after 10,000 cycles at 1C and 5C), and extremely high–rate stability (80% capacity retention after 30,000 cycles at 50C), demonstrating its promising application in sodium ion battery.

Gelation of Na-alginate aqueous solution: A study of sodium ion dynamics via NMR relaxometry

Sodium alginate (SA) hydrogels have a wide range of applications including tissue engineering, drug delivery and formulations for preventing gastric reflux. The dynamics of sodium ions during the gelation process of SA solution is critical for clarification of the gelation procedure. In this work, nuclear magnetic resonance (NMR) relaxometry and pulsed-field-gradient (PFG) NMR diffusometry were used to investigate the dynamics of the sodium ions during the gelation of SA alginate. We find that sodium ions are in two different states with the addition of divalent calcium ions, corresponding to Ca2+ crosslinked and un-crosslinked regions in the hydrogels. The sodium ions within the un-crosslinked regions are those released from the alginate chains without Ca2+ crosslinking. The relative content of sodium ions within the Ca2+ crosslinked regions decreased with the increase in the content of calcium ions in the system. The relaxation time T2 of sodium ions within the Ca2+ crosslinked and un-crosslinked regions shift to shorter and longer relaxation time with the increase in concentration of calcium ion, which indicates the closer package of SA chains and the larger space for the diffusion of free sodium ions. This work clarifies the dynamics of 23Na+ in a calcium alginate gel at the equilibrium state.

Multiply Reduced Oligofluorenes: Their Nature and Pairing with THF-Solvated Sodium Ions

Conjugated oligofluorenes are chemically reduced up to five charges in tetrahydrofuran solvent and confirmed with clear spectroscopic evidence. Stimulated by these experimental results, we have conducted a comprehensive computational study of the electronic structure and the solvation structure of representative oligofluorene anions with a focus on the pairing between sodium ions and these multianions. Using density functional theory (DFT) methods and a solvation model of both explicit solvent molecules and implicit polarizable continuum, we first elucidate the structure of tightly solvated free sodium ions, and then explore the pairing of sodium ions either in contact with reduced oligofluorenes or as solvent-separated ion pairs. Computed time-dependent-DFT absorption spectra are compared with experiments to assign the dominant ion pairing structure for each multianion. Computed ion pair binding energies further support our assignment. The availability of different length and reducing level of oligofluorenes enables us to investigate the effects of total charge and charge density on the binding with sodium ions, and our results suggest both factors play important roles in ion pairing for small molecules. However, as the oligofluorene size grows, its charge density determines the binding strength with the sodium ion.

Effect of Surface Coating Strengthening on Humidity Resistance of Sodium Silicate Bonded Sand Cured by Microwave Heating

The microwave heating sodium silicate bonded sand (SSBS) process is regarded as the most likely molding sand to realize green casting, owing to its low sodium silicate addition, rapid hardening speed, high strength, and excellent collapsibility. However, SSBS can absorb water easily in the air at room temperature. A surface coating strengthening method was used to improve the humidity resistance of SSBS. The properties of SSBS treated by the surface coating strengthening method were compared with that without any treatment. The experimental results indicated that humidity resistance had been improved greatly using the surface coating strengthening method, and comparing to SSBS without any treatment, the compressive strength (σ6h) of the treated SSBS increased 2.32 times and the moisture absorption rate (w6h) can be decreased by 45%. The morphology results revealed that there was a surface coating around the treated SSBS. The linear scanning indicated that the nonhygroscopic coat components presented on the boundary of the treated SSBS, and the surface phase analysis manifested that the boundary of the treated SSBS emerged new three phases, including Al2TiO5, PbTiO3, and NaAlO2, which reduced the free sodium ion content and improved the humidity resistance of SSBS.

Triple-quantum-filtered sodium imaging at 9.4 Tesla.

Efficient acquisition of triple-quantum-filtered (TQF) sodium images at ultra-high field (UHF) strength. A three-pulse preparation and a stack of double-spirals were used for the acquisition of TQF images at 9.4 Tesla. The flip angles of the TQ preparation were smoothly reduced toward the edge of k-space along the partition-encoding direction. In doing so, the specific absorption rate could be reduced while preserving the maximal signal intensity for the partitions most relevant for image contrast in the center of k-space. Simulations, phantom and in vivo measurements were used to demonstrate the usefulness of the proposed method. A higher sensitivity (∼ 20%) was achieved compared to the standard acquisition without flip angle apodization. Signals from free sodium ions were successfully suppressed irrespective of the amount of apodization used. B0 corrected TQF images with a nominal resolution of 5 × 5 × 5 mm(3) and an acceptable signal-to-noise ratio could be acquired in vivo within 21 min. Conventional TQF in combination with flip angle apodization permits to exploit more efficiently the increased sensitivity available at 9.4T.

Theoretical Investigation on the Structural Stability of Na2+X C6O6 As a Sodium-Ion Battery Cathode

Lithium-ion batteries play a vital role in our daily life due to their broad applicability as power sources for portable electronic devices and electric vehicles. However, the use of lithium-ion batteries in large scale application is currently under debate due to the high cost of lithium and its possible supply risk. Thus, minor-metal free or low-cost materials that can be derived from more abundant resources have become increasingly desirable along with the world's growing ecological concerns. Sodium-ion batteries have been explored as a promising alternative to lithium-ion batteries because there is no doubt that the sodium resources are inexhaustible and unlimited everywhere around the world. However, its ionic volume is almost double and its atomic mass is triple than that of lithium. Hence, it has been difficult to find an insertion host that can readily accept repeated insertion and extraction of the large sodium-ion into the matrix. Recently, it has been reported that disodium rhodizonate, Na2C6O6, exhibit good electrochemical properties and cycle performance as a rare organic cathode for sodium-ion batteries [1]. The minor-metal free Na2C6O6 can be considered as a promising cathode candidate for high cost performance sodium-ion batteries. However, its crystal structures during discharge/charge cycle, which correspond to Na2+x C6O6 (0 < x < 2) in composition, still remain unclear. In this work, we theoretically propose feasible crystal structures of Na2+x C6O6 during discharge/charge processes and show their electronic structures. Density functional theory calculations have been performed using the full-potential linearized augmented plane wave method [2, 3]. As a result of total energy calculations for Na2+x C6O6 with several space groups, we have found a structural phase transition: The most stable structure for Na4C6O6 has a different C6O6 packing arrangement from that in Na2C6O6. Our calculations have also revealed that the calculated electronic structure of Na2C6O6 crystal is quite analogous to that of a C6O6 molecule. Na2C6O6 has a stable structure where bonding states around Fermi level are filled and antibonding states are not. If Na insertion occurs without the structural phase transition, additional electrons would occupy antibonding states, resulting in unstable structure. On the other hand, the calculated electronic structure of Na4C6O6 is similar to that of two stacked C6O6 molecules. In this C6O6 frame, additional electrons can occupy new bonding states which arise from two stacked C6O6. Consequently, this structural phase transition, i.e. two stacked C6O6, allows for Na-ion insertion. Moreover, electrode potentials vs. Na/Na+ of Na2+x C6O6 have been evaluated. The calculated electrode potentials are consistent well with experimental results. Our predictions from first-principles calculations could be the key to understanding the mechanism of the discharge/charge process for Na2+x C6O6 cathode and be of benefit to the application of the minor-metal free sodium-ion batteries.Reference[1] K. Chihara, N. Chujo, A. Kitajou, and S. Okada, Electrochim. Acta 110, 240 (2013).[2] E. Wimmer, H. Krakauer, M. Weinert, and A. J. Freeman, Phys. Rev. B 24, 864 (1981).[3] J. M. Soler and A. R. Williams, Phys. Rev. B 40, 1560 (1989).

Corticosteroids increase intracellular free sodium ion concentration via glucocorticoid receptor pathway in cultured neonatal rat cardiomyocytes

BackgroundGlucocorticoids as well as mineralocorticoid have been shown to play essential roles in the regulation of electrical and mechanical activities in cardiomyocytes. Excess of these hormones is an independent risk factor for cardiovascular disease. Intracellular sodium ([Na+]i) kinetics are involved in cardiac diseases, including ischemia, heart failure and hypertrophy. However, intrinsic mediators that regulate [Na+]i in cardiomyocytes have not been widely discussed. Moreover, the quantitative estimation of altered [Na+]i in cultured cardiomyocytes and the association between the level of [Na+]i and the severity of pathological conditions, such as hypertrophy, have not been precisely reported. Methods and resultsWe herein demonstrate the quantitative estimation of [Na+]i in cultured neonatal rat cardiomyocytes following 24 h of treatment with corticosterone, aldosterone and dexamethasone. The physiological concentration of glucocorticoids increased [Na+]i up to approximately 2.5 mM (an almost 1.5-fold increase compared to the control) in a dose-dependent manner; this effect was blocked by a glucocorticoid receptor (GR) antagonist but not a mineralocorticoid receptor antagonist. Furthermore, glucocorticoids induced cardiac hypertrophy, and the hypertrophic gene expression was positively and significantly correlated with the level of [Na+]i. Dexamethasone induced the upregulation of Na+/Ca2 + exchanger 1 at the mRNA and protein levels. ConclusionsThe physiological concentration of glucocorticoids increases [Na+]i via GR. The dexamethasone-induced upregulation of NCX1 is partly involved in the glucocorticoid-induced alteration of [Na+]i in cardiomyocytes. These results provide new insight into the mechanisms by which glucocorticoid excess within a physiological concentration contributes to the development of cardiac pathology.

A technique for quantifying intracellular free sodium ion using a microplate reader in combination with sodium-binding benzofuran isophthalate and probenecid in cultured neonatal rat cardiomyocytes

BackgroundIntracellular sodium ([Na+]i) kinetics are involved in cardiac diseases including ischemia, heart failure, and hypertrophy. Because [Na+]i plays a crucial role in modulating the electrical and contractile activity in the heart, quantifying [Na+]i is of great interest. Using fluorescent microscopy with sodium-binding benzofuran isophthalate (SBFI) is the most commonly used method for measuring [Na+]i. However, one limitation associated with this technique is that the test cannot simultaneously evaluate the effects of several types or various concentrations of compounds on [Na+]i. Moreover, there are few reports on the long-term effects of compounds on [Na+]i in cultured cells, although rapid changes in [Na+]i during a period of seconds or several minutes have been widely discussed.FindingsWe established a novel technique for quantifying [Na+]i in cultured neonatal rat cardiomyocytes attached to a 96-well plate using a microplate reader in combination with SBFI and probenecid. We showed that probenecid is indispensable for the accurate measurement because it prevents dye leakage from the cells. We further confirmed the reliability of this system by quantifying the effects of ouabain, which is known to transiently alter [Na+]i. To illustrate the utility of the new method, we also examined the chronic effects of aldosterone on [Na+]i in cultured cardiomyocytes.ConclusionsOur technique can rapidly measure [Na+]i with accuracy and sensitivity comparable to the traditional microscopy based method. The results demonstrated that this 96-well plate based measurement has merits, especially for screening test of compounds regulating [Na+]i, and is useful to elucidate the mechanisms and consequences of altered [Na+]i handling in cardiomyocytes.