Ion Transport Research Articles

Freestanding Phosphonium Covalent Organic Frameworks with Efficient Hydroxide Conduction for Zinc–Air Batteries

Owing to their well‐defined crystalline pore structures and ordered functional ionic groups along the skeleton, ionic covalent organic frameworks (iCOFs) exhibit excellent performance and have significant potential for use in energy storage and conversion devices. Herein, we for the first time developed cationic phosphonium COFs with high hydroxide conduction even with low ion exchange capacity (IEC). Specifically, we synthesized COFs containing quaternary phosphonium groups as excellent ion transport moieties. Then, we fabricated freestanding phosphonium membranes through a vapor‐assisted method, which exhibited high hydroxide conductivity of 126 mS cm–1 at 80 °C from a minimal IEC of 1.17 mmol g–1. The resulting film was successfully applied to zinc–air batteries, demonstrating energy density of 96.1 mW cm–2, specific capacity of 95.0 mAh cm–2, and stable operation over 2,300 min. Overall, in addition to investigating a novel cationic functional group, we demonstrated a freestanding film formation method of COF‐based materials. The findings can provide a solid foundation for advancing the field of iCOFs to ion transport and promoting electrochemical applications.

Composite Solid-State Electrolyte with Vertical Ion Transport Channels for All-Solid-State Lithium Metal Batteries.

Composite solid electrolytes (CSEs) consisting of polymers and fast ionic conductors are considered a promising strategy for realizing safe rechargeable batteries with high energy density. However, randomly distributed fast ionic conductor fillers in the polymer matrix result in tortuous and discontinuous ion channels, which severely constrains the ion transport capacity and restricts its practical application. Here, CSEs with highly loaded vertical ion transport channels are fabricated by magnetically manipulating the alignment of Li0.35La0.55TiO3 nanowires. The construction of densely packed, vertically aligned ion transport channels can effectively enhance the ion transport capacity of the electrolyte, thereby significantly increasing ionic conductivity. At room temperature (RT), the presented CSE exhibits a remarkable ionic conductivity of up to 2.5 × 10-4 S cm-1. The assembled LiFePO4/Li cell delivers high capacities of 118 mAh g-1 at 5 C at 60°C and a RT capacity of 115 mAh g-1 can be achieved at a charging rate of 0.5 C. This work paves an encouraging avenue for further development of advanced CSEs that favor lithium metal batteries with high energy density and electrochemical performance.

Effect of hypernatremia on protein reabsorption in renal proximal tubules of the lake frog <I>Pelophylax ridibundus</I>

Protein reabsorption in the kidney proximal tubules occurs simultaneously with the transport of ions and water, but little is known about the dependence of receptor-mediated protein endocytosis on water-salt balance changes. The aim of the study was to investigate tubular reabsorption and intracellular vesicular transport of various proteins in a model of hypernatremia in lake frogs (Pelophylax ridibundus). Frogs were injected with hypertonic sodium chloride solution (0.75 M NaCl) 1 hour before injection of green or yellow fluorescent proteins (GFP or YFP), as well as lysozyme. The method of fluorescent immunohistochemistry was used for detection of lysozyme and endocytic receptor megalin in kidney sections. Specimens were investigated using laser scanning confocal microscopy. The intensity of fluorescent signals of proteins and megalin in proximal tubular cells was determined on the images obtained. To study the dynamics of endocytosis, an automated method for quantifying colocalized protein and megalin signals was used. A statistically significant decrease in the reabsorption of GFP, YFP and lysozyme in the proximal tubules after 0.75 M of NaCl injection was found. The accumulation of proteins in the early endocytic compartment and decrease in their entry into late endosomes and lysosomes are shown, that is considered as evidence of a delay in intracellular vesicular transport in hypernatremia. The data obtained were analyzed in connection with changes in blood parameters and kidney activity during osmoregulation, and also with the role of chloride channels in receptor-mediated protein endocytosis. It can be assumed that increased ion transport in the proximal tubules cells in hypernatremia leads to decreased reabsorption capacity of epitheliocytes and delayed intracellular transport of proteins.

Na3.5(MnVFeTi)0.5(PO4)3: A Multi‐Transition‐Metal‐Ion‐Engineered NASICON‐Type Cathodes for Sodium Ion Batteries

AbstractElectrochemically active Na‐superionic conductor (NASICON)‐type cathodes have the structural flexibility to include various transition elements, thus enabling high power outputs benefited by multi‐electron redox reactions. This study amalgamated multiple transition metal ions to construct a new NASICON‐type cathode i. e., carbon coated Na3.5(MnVFeTi)0.5(PO4)3 (NMVFTP/C) for Na‐ion batteries (NIBs). The NMVFTP/C cathode engineered in this study demonstrated stable Na+‐storage capacity, including long‐term cycling stability up to 4000 cycles at 3000 mA g−1 with 96 % capacity retention and a high‐rate output capacity of 85.16 mAh g−1 at 2500 mA g−1. To elucidate the ion transport process within the cathode, density functional theory modeling was employed. The low energy barrier for the diffusion of Na+ in the NMVFTP/C materials was proved to be a key factor supporting our material's superior electrochemical performances.

In‐Situ Self‐Respiratory Solid‐to‐Hydrogel Electrolyte Interface Evoked Well‐Distributed Deposition on Zinc Anode for Highly Reversible Zinc‐Ion Batteries

AbstractThe aqueous zinc‐ion batteries (AZIB) have emerged as a promising technology in the realm of electrochemical energy storage. Despite its potential advantages in terms of safety, cost‐effectiveness, and inherent safety, AZIB faces significant challenges. Issues attributed to unsupported thermodynamics and non‐uniform potential distribution and deposition, present formidable obstacles that necessitate resolution. To tackle these challenges, a novel strategy adapting hybrid organic–inorganic in situ derived solid‐to‐hydrogel electrolyte interface (StHEI) has been developed from coordination reactions and self‐respiratory process, establishing uniform diffusion channels by ion bridges and accelerating ion transport. Self‐respiratory pattern of StHEI realized through in situ inorganic component conversion further prolongs the protecting duration, which effectively mitigates corrosion and passivation but enhance the mechanical properties of the StHEI measured through Young's modulus. This novel StHEI promotes well‐distributed potential lines within the Helmholtz regions. Zn2+ are finally induced to deposit and nucleate in a compact, fine, and uniform manner. Asymmetrical batteries assembled with the modified Zn electrode and bare Zn exhibit exceptional stability over 3000 h (1 mA cm−2–0.5 mAh cm−2). The asymmetrical Cu//Zn cell achieved an outstanding average Coulombic efficiency (CE) of 99.6 % over 1200 cycles.

In-Situ Self-Respiratory Solid-to-Hydrogel Electrolyte Interface Evoked Well-Distributed Deposition on Zinc Anode for Highly Reversible Zinc-Ion Batteries.

The aqueous zinc-ion batteries (AZIB) have emerged as a promising technology in the realm of electrochemical energy storage. Despite its potential advantages in terms of safety, cost-effectiveness, and inherent safety, AZIB faces significant challenges. Issues attributed to unsupported thermodynamics and non-uniform potential distribution and deposition, present formidable obstacles that necessitate resolution. To tackle these challenges, a novel strategy adapting hybrid organic-inorganic in situ derived solid-to-hydrogel electrolyte interface (StHEI) has been developed from coordination reactions and self-respiratory process, establishing uniform diffusion channels by ion bridges and accelerating ion transport. Self-respiratory pattern of StHEI realized through in situ inorganic component conversion further prolongs the protecting duration, which effectively mitigates corrosion and passivation but enhance the mechanical properties of the StHEI measured through Young's modulus. This novel StHEI promotes well-distributed potential lines within the Helmholtz regions. Zn2+ are finally induced to deposit and nucleate in a compact, fine, and uniform manner. Asymmetrical batteries assembled with the modified Zn electrode and bare Zn exhibit exceptional stability over 3000 h (1 mA cm-2-0.5 mAh cm-2). The asymmetrical Cu//Zn cell achieved an outstanding average Coulombic efficiency (CE) of 99.6 % over 1200 cycles.

Addressing cadmium stress in rice with potassium-enriched biochar and Bacillus altitudinis rhizobacteria.

Cadmium (Cd) is a potentially harmful metal with significant biological toxicity that adversely affects plant growth and physiological metabolism. Excessive Cd exposure in plants leads to stunted plant growth owing to its negative impact on physiological functions such as photosynthesis, nutrient uptake, and water balance. Potassium-enriched biochar (KBC) and Bacillus altitudinis rhizobacteria (RB) can effectively overcome this problem. Potassium-enriched biochar (KBC) significantly enhances plant growth by improving the soil structure, encouraging water retention, and enhancing microbial activity as a slow-release nutrient. Rhizobacteria promote plant growth by improving root ion transport and nutrient availability while promoting soil health and water conservation through RB production. This study examined the effects of combining RB + KBC as an amendment to rice, both with and without Cd stress. Four treatments (control, KBC, RB, and RB + KBC) were applied using a completely randomized design (CRD) in four replications. The results showed that the combination of RB + KBC increased rice plant height (38.40%), shoot length (53.90%), and root length (12.49%) above the control under Cd stress. Additionally, there were notable improvements in chlorophyll a (15.31%), chlorophyll b (25.01%), and total chlorophyll (19.37%) compared to the control under Cd stress, which also showed the potential of RB + KBC treatment. Moreover, increased N, P, and K concentrations in the roots and shoots confirmed that RB + KBC could improve rice plant growth under Cd stress. Consequently, these findings suggest that RB + KBC is an effective amendment to alleviate Cd stress in rice. Farmers should use RB + KBC to achieve better rice growth under cadmium stress.

High‐Performance Synaptic Devices Based on Cross‐linked Organic Electrochemical Transistors with Dual Ion Gel

AbstractOrganic electrochemical transistors (OECTs) represent a promising approach for flexible, wearable, biomedical electronics, and sensors integrated with diverse substrates. Their ability to operate at low voltages and interact effectively with biological systems makes them particularly suitable for neuromorphic applications. For neuromorphic devices, OECTs must enhance electrical performance, biocompatibility, and signal storage/erasure capabilities. While UV cross‐linking methods with various side effects on organic semiconductors are predominant in improving mobility and current retention time, thermal cross‐linking based on the solution process has not been extensively explored. Additionally, despite significant research on the modification of electrolyte property, the ionic charge compensation mechanisms between multiple electrolytes are still unclear. This study employs a cross‐linking strategy involving the chemical reaction of poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) with di‐tert‐butyl‐peroxide (DTBP) to create a cross‐linked P3HT active layer. Furthermore, a dual ion gel structure combining a conventional ion gel with a chitosan‐based ion gel is investigated for increased ionic transport to enhance OECT performance. Using the above two methods, the enhanced electrical performance showing the mobility of 25 F cm−1 V−1 s−1 and synaptic properties showing long‐term plasticity of cross‐linked OECTs with a dual ion gel structure are demonstrated, suggesting their potential application as high‐performance neuromorphic devices.

Facile synthesis and characterization of zinc molybdate (ZnMoO4) nanosheets for electrochemical supercapacitor application

Abstract This study explores the synthesis and characterization of zinc molybdate (ZnMoO4) nanosheets with emphasis on their potential application for energy storage devices particularly supercapacitors. The synthesis of ZnMoO4 nanosheets was done through co-precipitation followed by examination of their structure, morphology, optical, thermal behaviour and electrochemical performance by various characterization techniques. X-ray diffraction (XRD) analysis confirmed that the formation of monoclinic ZnMoO4 phase with the average crystallite size 17.93 nm. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) revealed that this material had nanosheets-like structure which helps to increase ion transport and surface area; these two factors are essential for enhancing the material’s supercapacitor efficacy. The semiconductor characteristics were determined using UV–Visible diffuse reflectance spectroscopy (UV-DRS) which indicated a band gap energy of 4.2 eV. Fourier transform infrared (FTIR) analysis confirmed that the presence of Zn–O and Mo–O bonds in their crystal lattice. Thermogravimetric analysis (TGA) showed that the ZnMoO4 nanosheets had thermal stability since they experienced only a slight mass loss of 2.57 % up to 800 °C. Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests were undertaken to find out the specific capacitance and the value is 618 F g⁻1 at a current density of 1 A g⁻1.

Computational engineering of water-soluble human potassium ion channels through QTY transformation.

Transmembrane potassium ion channels are crucial for ion transport, metabolism, and signaling, and serve as promising targets for anti-cancer therapies. However, their hydrophobic transmembrane nature requires detergents, posing a major bottleneck for experimental handling. In this paper, we present a structural bioinformatics study of six experimentally determined and twelve modeled potassium channel structures, in which hydrophobic amino acids (L, I/V, and F) were systematically replaced with neutral hydrophilic ones (Q, T, and Y), making the proteins more water-soluble. QTY (computationally predicted) and native (experimental and repredicted) variants show remarkable structural similarity (RMSD: ~0.50 Å - ~2.14 Å) despite significant sequence differences. QTY variants, both rigid and refined with MD simulations, maintain comparable to native variants stability, solvent-accessible surface area (SASA), and ionic, aromatic, and van der Waals interactions but differ in the grand average of hydropathy (GRAVY), solubility, and hydrophobic contacts. Overall, our study presents a computational approach for designing hydrophilic potassium ion channels while maintaining the native global structure that could potentially simplify their practical use by eliminating the need for detergents.

A Multifunctional Na2Se/Zn-Mn Skeleton Enables Processable and Highly Reversible Sodium Metal Anode.

The recent high-energy density sodium (Na) metal batteries (SMBs) are restricted by their processability, lifetime, and safety. These issues can be addressed by controlling the reactions at the Na metal by modifying the Na metal anode (SMA) with the sodiophilic hosts. Herein, a multifunctional Na2Se/Zn-Mn skeleton is introduced for SMA and fabricate a processable Na@Na2Se/Zn-Mn composite using repeated cold rolling/folding approach through the spontaneous reaction between Na metal and ZnMnSe alloy. This unique intermetallic composite has Zn and Mn metal sites for uniform deposition of Na, while Na2Se generates a stable SEI for rapid Na+ ion transport. It offers outstanding sodiophilicity, high processability, excellent mechanical strength, and high ionic conductivity due to the synergistic effect of multi-component, enabling stable Na plating/stripping at high current densities and areal capacities. An optimized Na2Se/Zn-Mn skeleton enables Na||Na symmetric cells to attain a high critical current density of 5.0mA cm-2 at 5.0 mAh cm-2 with an extended lifespan of 9000h at 1.0mA cm-2 at 1.0 mAh cm-2. Remarkably, when configured into a full cell with a Na3V2(PO4)3 cathode, the SMB displays an extended lifespan of 2000 cycles at 10 C and an impressive high-rate capacity of ≈61.6 mAh g-¹ at 30 C.

ZnO Quantum Dots as PEO-Based Solid Electrolytes Fillers for Lithium Metal Batteries.

PEO-based solid polymer electrolyte (PEO SPE) is regarded as one of the most promising solid electrolytes due to its exceptional flexibility, cost-effectiveness, and ease of integration. However, its commercialization is hindered by inadequate ionic conductivity and unstable interface. By incorporating proper ZnO quantum-dots (QDs) fillers with enhanced surface activity, the ion transport inner the PEO-based electrolyte can be improved along with enhanced REDOX kinetics at the Li/PEO interface. The ionic conductivity reaches 5.97×10-4 S cm-1 at 60 °C. Moreover, ZnO QDs exhibit a quantum size effect and possess lithiophilic characteristics that promote uniform nucleation and redeposition of Li+ while forming a stable Li-Zn alloy. This inhibits lithium dendrite formation and enhances the stability of Li anode. Li//Li cell with 3 % ZnO QDs works steadily for more than 2100 h at 60 °C with 0.1 mA cm-2. The assembled Li//LiFePO4 cell provides a reversible capacity of 134.91 mAh g-1 after200 cycles at 0.1 C.

Understanding pillar chemistry in potassium-containing polyanion materials for long-lasting sodium-ion batteries.

K-containing polyanion compounds hold great potential as anodes for sodium-ion batteries considering their large ion transport channels and stable open frameworks; however, sodium storage behavior has rarely been studied, and the mechanism remains unclear. Here, using a noninterference KTiOPO4 thin-film model, the Na+ storage mechanism is comprehensively revealed by in situ/operando spectroscopy, aberration-corrected electron microscopy and density functional theory calculations. We find that incomplete K+/Na+ ion exchange occurs and eventually 0.15 K+ remains as a pillar to stabilize the tunnel structure. The pillar effect substantially maintains the volume change within 3.9%, much smaller than that of K+(Na+) insertion into KTiOPO4(NaTiOPO4) (9.5%; 5%), thus enabling 10,000 cycles. The powder electrode demonstrates comparable capacity and can work efficiently at commercial-level areal capacity of 2.47 mAh cm-2. The quasi-solid-state pouch cell with high safety under extreme abuse also manifests long-term cycling stability. This pillar chemistry will inspire alkali metal ion storage in hosts containing heterogeneous cations.

Crystalline Electrolyte Boosts High Performance of All-Solid-State Lithium-Ion Batteries.

The rigid solid-solid contact at the interface between the solid electrolyte and electrodes in full-solid-state lithium-ion batteries (ASSBs) presents a considerable challenge to lithium ion transport. To address this, we propose using Li-concentrated succinonitrile (Li-SN45) as an efficient bilateral interface modifier in ASSBs. This material boasts exceptional ionic conductivity of 3.38 mS cm-1 and excellent corrosion resistance to the Li metal anode. The assembled ASSBs using layered cathodes and Li metal demonstrate outstanding discharge capacity (170 mAh g-1 @ 20 mA g-1) and superior long-term cycling performance (97% capacity retention after 100 cycles). MALDI-TOF results suggest the formation of a crystalline structure in Li-SN45, which facilitates smooth "anion-free" Li+ hopping paths assisted by the oxygen atoms, as revealed by the solved crystal structure. Our findings enriched the understanding of Li transport dynamics in electrolytes of ASSBs, paving the way to designing superior next-generation ASSBs with fast Li transport.

Intercalation of Polyacrylonitrile Nanoparticles in Ti3C2Tx MXene Layers for Improved Supercapacitance.

We report the intercalation of polyacrylonitrile nanoparticles in Ti3C2Tx MXene layers through simple sonication. The use of polyacrylonitrile, which was synthesized via radical polymerization, offered dual benefits: (1) It increased the interlayer spacing of MXene, thereby exposing more surface area and enhancing ion transport channels during charge and discharge cycles, and (2) Integrating MXene with polyacrylonitrile enables the creation of a composite with conductive properties, following percolation principle. X-ray diffraction analysis showed an increase in the c-lattice parameter, indicative of the interlayer spacing, from 22.31 Å for the pristine MXene to 37.73 Å for the MXene-polyacrylonitrile composite. The intercalated polyacrylonitrile nanoparticles facilitated the delamination by weakening the interlayer interactions, especially during sonication. Electrochemical assessments revealed significant improvement in the properties of the MXene-polyacrylonitrile composite compared to the pristine MXene. The assembled asymmetric device achieved a good specific capacitance of 32.1 F/g, an energy density of 11.42 W h/kg, and 82.2% capacitance retention after 10,000 cycles, highlighting the practical potential of the MXene-polyacrylonitrile composite.

2-Acetamidophenol (2-AAP) Suppresses the Progression of Atherosclerosis by Alleviating Hyperlipidemia and Attenuating the Ferroptosis Pathway

Hyperlipidemia and consequent endothelial inflammation, along with foam cell generation, promote the progression of atherosclerosis (AS). Here, we aimed to investigate the effects of 2-acetamidophenol (2-AAP), which was selected by zebrafish phenotypic screening, in alleviating AS by relieving hyperlipidemia and inhibiting foam cell formation, as well as the underlying mechanisms. In a zebrafish hyperlipidemia model, 2-AAP increased lipid-lowering efficacy; alleviated TC, TG, LDL-C, and MDA levels; elevated HDL-C and T-SOD levels; significantly improved intravascular macrophage aggregation; and improved blood flow. In an ox-LDL-induced RAW264.7 model, 2-AAP inhibited lipid phagocytosis in RAW264.7 cells; reduced the intracellular TC, TG, FC, and CE contents; and decreased the CE/TC ratio, thus slowing foam cell generation. In addition, 2-AAP alleviated intracellular ROS and ferrous ion accumulation in RAW264.7 cells, reduced the MDA content, and increased GPX4 viability. Furthermore, transcriptome analyses and gene expression validation showed 2-AAP treatment upregulates genes related to GSH synthesis and transport, such as gclc, gclm, gss, and gpx4a, and enhanced the expression levels of genes involved in the storage and transportation of iron ions, such as fpn1, fth, and g6pd, indicating that 2-AAP dramatically regulated the ferroptosis and glutathione metabolic pathways. Overall, our study demonstrated that 2-AAP demonstrated potential in AS by alleviating hyperlipidemia and attenuating the ferroptosis pathway and provided evidence supporting the future application of 2-AAP in AS treatment.

Hydrogen peroxide disrupts the regulatory pathway of saliva secretion in two salivary acinar rat cell lines

BackgroundSecretion of saliva is controlled by autonomic nerve signals via regulation of Ca2+-dependent ion transport across acinar cell membranes. Oxidative stress may affect this process, leading to a decrease in saliva production. This study investigates elements of the Ca2+ regulatory pathway and their vulnerability to hydrogen peroxide-induced oxidative stress.MethodsRat parotid and submandibular salivary gland acinar cell lines were exposed to different hydrogen peroxide concentrations to simulate oxidative stress. Cell viability and intracellular reactive oxygen species were measured, mRNA levels were assessed via RT-qPCR, and protein expression was studied using western blot and immunofluorescence microscopy.ResultsElevated concentrations of hydrogen peroxide reduced cell viability and increased intracellular levels of reactive oxygen species and led to a decrease in cholinergic receptor muscarinic 3 and adrenoreceptor alpha 1A mRNA and protein levels in both cell lines. In parotid gland cells, both mRNA and protein levels of stromal interaction molecule 1 and Orai1 decreased with increasing concentrations of hydrogen peroxide. In contrast, in submandibular gland cells stromal interaction molecule 1 and Orai1 displayed differential mRNA and protein expression levels.ConclusionOur study revealed that hydrogen peroxide exposure alters rat parotid and submandibular acinar cells, increasing reactive oxygen species and reducing autonomic receptor expression. Differential mRNA and protein expression of stromal interaction molecule 1 and Orai1 highlight complex oxidative stress effects on Ca2⁺ signaling. Most likely these effects will be deleterious to salivary secretion, but some effects may be protective.

Advanced Eutectogel Electrolyte for High‐Performance and Wide‐Temperature Flexible Zinc‐Air Batteries

AbstractDespite ongoing challenges, achieving further breakthroughs in the development of gel polymer electrolytes with a wide temperature range, excellent liquid retention capability and enhanced anode compatibility in flexible zinc‐air batteries (FZABs) remains a significant objective. This study presents a significant advancement in the development of choline chloride/ethylene glycol‐polyvinyl alcohol (ChCl/EG‐PVA) eutectogel electrolyte, tailored for high‐performance operation across a wide temperature range. Systematic in‐situ and ex‐situ characterizations and theoretical simulations confirm the formation of robust hydrogen bonding and denser polymer cross‐linked networks within the prepared eutectogel, leading to enhanced liquid retention ability (93.7 % after 96 h exposure to air) and ion transport capacity (ionic conductivity of 171.3 mS cm−1). Additionally, the zincophilicity nature of the choline cation in eutectogel effectively suppresses dendrites growth. The assembled FZAB utilizing this eutectogel electrolyte achieves a peak power density of 109.3 mW cm−2 and a cycle life of 90 h. Notably, the power density of FZAB is maintained as high as 38.2 mW cm−2 at −40 °C and 63.2 mW cm−2 at 50 °C, demonstrating its prominent suitability for applications in extreme temperature conditions. The design of eutectogel provides a novel way to achieve the high‐performance FZAB.

Modeling Electrochemical Impedance Spectroscopy Using Time-Dependent Finite Element Method

A time-dependent electrochemical impedance spectroscopy (EIS) model is presented using the finite element method (FEM) to simulate a 2D interdigitated electrode in an aqueous NaCl electrolyte. Developed in COMSOL Multiphysics, the model incorporates ion transport, electric field distribution, Stern layer effects, and electrode sheet resistance, governed by the Poisson and Nernst–Planck equations. This model can predict the transient current response to an applied excitation voltage, which gives information about the dynamics of the electrochemical system. The simulation results are compared with the experimental data, reproducing key features of the measurements. The transient current response indicates the need for multiple excitation cycles to stabilize the impedance measurement. At low frequencies (<1 kHz), the voltage drop at the Stern layer is significant, while at higher frequencies (>100 kHz), the voltage drop due to sheet resistance dominates. Moreover, the amplitude of the excitation voltage influences the EIS measurement, higher amplitudes (above 0.1 V) lead to non-linear impedance behavior, particularly at low ion concentrations. Discrepancies at low frequencies suggest that Faradaic processes may need to be incorporated for improved accuracy. Overall, this model provides quantitative insights for optimizing EIS sensor design and highlights critical factors for high-frequency and low-concentration conditions, laying the foundation for future biosensing applications with functionalized electrodes.

Copper homeostasis and neurodegenerative diseases

Copper, one of the most prolific transition metals in the body, required for normal brain physiological activity and allows various functions to work normally through its range of concentrations. Copper homeostasis is meticulously maintained through a complex network of copper-dependent proteins, including copper transporters (CTR1 and CTR2), the two copper ion transporters the Cu -transporting ATPase 1 (ATP7A) and Cu-transporting beta (ATP7B), and the three copper chaperones ATOX1, CCS, and COX17. Disruptions in copper homeostasis can lead to either the deficiency or accumulation of copper in brain tissue. Emerging evidence suggests that abnormal copper metabolism or copper binding to various proteins, including ceruloplasmin and metallothionein, is involved in the pathogenesis of neurodegenerative disorders. However, the exact mechanisms underlying these processes are not known. Copper is a potent oxidant that increases reactive oxygen species production and promotes oxidative stress. Elevated reactive oxygen species levels may further compromise mitochondrial integrity and cause mitochondrial dysfunction. Reactive oxygen species serve as key signaling molecules in copper-induced neuroinflammation, with elevated levels activating several critical inflammatory pathways. Additionally, copper can bind aberrantly to several neuronal proteins, including alpha-synuclein, tau, superoxide dismutase 1, and huntingtin, thereby inducing neurotoxicity and ultimately cell death. This study focuses on the latest literature evaluating the role of copper in neurodegenerative diseases, with a particular focus on copper-containing metalloenzymes and copper-binding proteins in the regulation of copper homeostasis and their involvement in neurodegenerative disease pathogenesis. By synthesizing the current findings on the functions of copper in oxidative stress, neuroinflammation, mitochondrial dysfunction, and protein misfolding, we aim to elucidate the mechanisms by which copper contributes to a wide range of hereditary and neuronal disorders, such as Wilson's disease, Menkes' disease, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, and multiple sclerosis. Potential clinically significant therapeutic targets, including superoxide dismutase 1, D-penicillamine (DPA), and 5,7-dichloro-2-[(dimethylamino)methyl]-8-hydroxyquinoline (PBT2), along with their associated therapeutic agents, are further discussed. Ultimately, we collate evidence that copper homeostasis may function in the underlying etiology of several neurodegenerative diseases and offer novel insights into the potential prevention and treatment of these diseases based on copper homeostasis.