Passage Of Ions Research Articles

Study of the Mechanisms of Radiation Softening and Swelling upon Irradiation of TiTaNbV Alloys with He2+ Ions with an Energy of 40 keV.

This paper presents simulation results of the ionization losses of incident He2+ ions with an energy of 40 keV during the passage of incident ions in the near-surface layer of alloys based on TiTaNbV with a variation of alloy components. For comparison, data on the ionization losses of incident He2+ ions in pure niobium, followed by the addition of vanadium, tantalum, and titanium to the alloy in equal stoichiometric proportions, are presented. With the use of indentation methods, the dependences of the change in the strength properties of the near-surface layer of alloys were determined. It was established that the addition of Ti to the composition of the alloy leads to an increase in resistance to crack resistance under high-dose irradiation, as well as a decrease in the degree of swelling of the near-surface layer. During tests on the thermal stability of irradiated samples, it was found that swelling and degradation of the near-surface layer of pure niobium affects the rate of oxidation and subsequent degradation, while for high-entropy alloys, an increase in the number of alloy components leads to an increase in resistance to destruction.

Enhancing asymmetric supercapacitor performance with NiCo2O4–NiO hybrid electrode fabrication

Spinel metal oxide with an extra crystalline phase is an active way to enhance the performance of the supercapacitor. Herein, a facile hydrothermal approach has been established for synthesizing nanocrystalline NiCo2O4 with an extra NiO phase material as the potential electrode for a supercapacitor. XRD analysis is executed to expose the crystalline environment and found to be dual phases ie. NiO and NiCo2O4. Further, the chemical environment of these phases is identified in FTIR, EDS, X-ray photoelectron spectroscopy, elemental mapping, and Raman analysis. The morphological analysis (SEM) of the material showed that the formation of tiny particulates aggregates become uniform in size, which consists of a nearly spherical structure. NiCo2O4–NiO showed a remarkable electrochemical performance in a 2 M potassium hydroxide. The maximum capacitance was achieved as 866 F/g at a sweep rate of 5 m V/s, which is quite higher than the normal pristine NiCo2O4. The material delivered a capacity retention of 85% over 5000 cycles. This high performance was attributed to the NiO phase in NiCo2O4 material inducing an additional charge at the boundary, prominent to synergistic effect and rapid electron and ion passage. Hence, overall, the superior performance with extra NiO phase could be beneficial for developing spinel metal oxide electrodes for battery-type supercapacitor applications.

Frequency-domain analysis of membrane polarization in two-compartment model neurons with weak alternating electric fields.

Transcranial alternating current stimulation (tACS) is widely used in studying brain functions and the treatment of neuropsychiatric diseases in a frequency-specific manner. However, how tACS works on neuronal activity has been poorly understood. In this paper, we use linear system analysis to investigate how weak alternating electric fields (EFs) affect the membrane polarization of neurons in the frequency domain. Two biophysically realistic conductance-based two-compartment models of cortical pyramidal neurons are developed to simulate subthreshold membrane polarization with weak alternating EFs. We linearize the original nonlinear models at the stable equilibrium points and further simplify them to the two- or three-dimensional linear systems. Thus, we calculate the transfer functions of the low-dimensional linear models to model neuronal polarization patterns. Based on the transfer functions, we compute the amplitude- and phase-frequency characteristics to describe the relationship between weak EFs and membrane polarization. We also computed the parameters (gain, zeros, and poles) and structures (the number of zeros and poles) of transfer functions to reveal how neuronal intrinsic properties affect the parameters and structure of transfer functions and thus the frequency-dependent membrane polarization with alternating EFs. We find that the amplitude and phase of membrane polarization both strongly depended on EF frequency, and these frequency responses are modulated by the intrinsic properties of neurons. The compartment geometry, internal coupling conductance, and ionic currents (except Ih) affect the frequency-dependent polarization by mainly changing the gain and pole of transfer functions. Larger gain contributes to larger amplitude-frequency characteristics. The closer the pole is to the imaginary axis, the lower phase-frequency characteristics. However, Ih changes the structure of transfer function in the dendrite by introducing a new pair of zero-pole points, which decrease the amplitude at low frequencies and thus lead to a visible resonance. These results highlight the effects of passive properties and active ion currents on subthreshold membrane polarization with alternating EFs in the frequency domain, which provide an explainable connection of how intrinsic properties of neurons modulate the neuronal input-output functions with weak EF stimulation.

Claudin Barriers on the Brink: How Conflicting Tissue and Cellular Priorities Drive IBD Pathogenesis.

Inflammatory bowel diseases (IBDs) are characterized by acute or chronic recurring inflammation of the intestinal mucosa, often with increasing severity over time. Life-long morbidities and diminishing quality of life for IBD patients compel a search for a better understanding of the molecular contributors to disease progression. One unifying feature of IBDs is the failure of the gut to form an effective barrier, a core role for intercellular complexes called tight junctions. In this review, the claudin family of tight junction proteins are discussed as they are a fundamental component of intestinal barriers. Importantly, claudin expression and/or protein localization is altered in IBD, leading to the supposition that intestinal barrier dysfunction exacerbates immune hyperactivity and disease. Claudins are a large family of transmembrane structural proteins that constrain the passage of ions, water, or substances between cells. However, growing evidence suggests non-canonical claudin functions during mucosal homeostasis and healing after injury. Therefore, whether claudins participate in adaptive or pathological IBD responses remains an open question. By reviewing current studies, the possibility is assessed that with claudins, a jack-of-all-trades is master of none. Potentially, a robust claudin barrier and wound restitution involve conflicting biophysical phenomena, exposing barrier vulnerabilities and a tissue-wide frailty during healing in IBD.

Microstructure optimization of bioderived polyester nanofilms for antibiotic desalination via nanofiltration

The successful implementation of thin-film composite membranes (TFCM) for challenging solute-solute separations in the pharmaceutical industry requires a fine control over the microstructure (size, distribution, and connectivity of the free-volume elements) and thickness of the selective layer. For example, desalinating antibiotic streams requires highly interconnected free-volume elements of the right size to block antibiotics but allow the passage of salt ions and water. Here, we introduce stevioside, a plant-derived contorted glycoside, as a promising aqueous phase monomer for optimizing the microstructure of TFCM made via interfacial polymerization. The low diffusion rate and moderate reactivity of stevioside, together with its nonplanar and distorted conformation, produced thin selective layers with an ideal microporosity for antibiotic desalination. For example, an optimized 18-nm membrane exhibited an unprecedented combination of high water permeance (81.2 liter m-2 hour-1 bar-1), antibiotic desalination efficiency (NaCl/tetracycline separation factor of 11.4), antifouling performance, and chlorine resistance.

New technique of ion identification in Accelerator Mass Spectrometry using low-pressure TPC with GEM readout

We have developed and successfully tested a low-pressure Time Projection Chamber (TPC) with Gas Electron Multiplier (GEM) readout for Accelerator Mass Spectrometry (AMS).AMS facility in Novosibirsk has a problem of separating isobar ions of different chemical elements that have the same atomic mass. The typical example is radioactive isotopes 10Be and 10B that are used to date geological objects at a time scale of ten million years. To solve this problem, a new ion identification technique, namely that based on measuring both ion track ranges and ion energies in low-pressure TPCs with GEM readout, has been developed. This technique is proposed to be applied in AMS for dating geological objects, namely for geochronology of Cenozoic era.In this work, we developed a new larger version of the TPC with a dedicated thin silicon nitride window for an efficient passage of ions. The TPC characteristics were studied in isobutane at low pressures using alpha particle sources. In addition, the use of GEM instead of THGEM has been shown to substantially improve the energy resolution at a nominal pressure (50 torr). Using these results and SRIM code simulations, it is shown that isobaric boron and beryllium ions can be effectively separated at AMS, providing efficient dating on a scale of ten million years. This technique will be applied in the AMS facility in Novosibirsk in the near future.

Microstructures, optical and electrochemical properties of advanced Fe0.8Se0.14Si0.06MoO4 nanocrystalline for energy storage applications

Technological progress has raised expectations regarding the growth of energy storage structures. Enhancing the energy density and surface area and producing a high specific capacitance supercapacitor is urgently demanded. The microstructural and optical properties of Fe0.8Se0.14Si0.06MoO4 nanocrystallites produced by the advanced sol-gel technique are investigated. XRD and TEM show that the nanocrystallites have a crystallite nanosize of 15.6 nm and a mean diameter of 14–23.6 nm for the formed monoclinic structure. The diffuse reflectance spectra of the synthesized Fe0.8Se0.14Si0.06MoO4 calcined at 650 °C for 2 h were measured in the range of 200 to 2500 nm. The type and value of the energy band gap were obtained from the diffuse reflectance spectra. Enhancing the energy density and surface area and producing a high specific capacitance of the supercapacitor is urgently required to develop unique positive and negative electroactive nanostructures. The formation of advanced Fe0.8Se0.14Si0.06MoO4 mesoporous structures with large surface areas and adjusted energy band gap could expand more electroactive locations, which supported the contact of the electrode-electrolyte and improved the ion and electron passage through the chemical reactions. The good electrochemical performance of Fe0.8Se0.14Si0.06MoO4 was exhibited with a high specific capacitance of 681.6 F g−1 at 1.0 A g−1. The specific capacitance decreased to 396.8 F g−1 after 1000 charge-discharge cycles at 1.0 A g−1. Therefore, Fe0.8Se0.14Si0.06MoO4 was suggested as a promising positive electrode material for energy storage applications.

Angstrom‐Level Ionic Sieve 2D‐MOF Membrane for High Power Aqueous Zinc Anode

AbstractAqueous Zn‐ion energy‐storage deviceswith metal Zn as anodes, including batteries and capacitors (ZIBs and ZICs), is largely hindered by dendritic growth and low coulombic efficiency since the side reactions between Zn anodes and electrolyte, originating fromthat targeted and efficient isolation of H2O and SO42− is extremely challenging. Herein, inspired by density functional theory (DFT) that the 2D angstrom level metal‐organic framework(2D‐MOF) is highly selective for the passage of ions, simultaneously excluding the SO42− and H2O but allowing Zn2+ selective conduction. Moreover, 2D‐MOF exhibits better mechanical strength compared with 3D‐MOF, which is more conducive to inhibit dendrite growth. Impressively, benefiting from the 2D‐MOFlayer, symmetric Zn cells survived up to 2000 h at 4 mA cm−2,near 20‐times that of bare Zn anodes. Coupling it with cathode for ZICs and ZIBs, excellent electrochemical performances are presented. Importantly, symmetric Na cells with 2D‐MOF as ionic sieve membrane also deliver small polarization and outstanding performance, indicating that this study provides an efficient strategy to develop long‐life metal anode.

CsPbBr3 nanocrystals as luminescent probe for in situ detection of chloride and iodide ions in water

All-inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) Perovskite nanocrystals (PNCs) are promising new luminescent nanomaterials. However, PNCs are less stable in ambient environments. The fully encapsulated protective layer greatly improves the stability but limits direct contact with substances in the environment, leading to great challenges for luminescent probe applications. We developed a simple approach that hydrogen-bond cross-linking reinforcement to deal with the challenge. Target ACD-PNCs, which use β-CD (β- cyclodextrin) as the ligand with addition of Arginine, were prepared by adding arginine to an ethanol solution of CsPbBr3 stabilized by β-CD. The ACD-PNCs have a luminescence efficiency of 82% and show good stability in external environments including high temperature, humidity, and ethanol–water mixed solvents. It is worth noting that neither arginine nor cyclodextrin alone could have allowed PNCs to perform so well. More interestingly, the hydrogen-bond network permits the passage of chloride and iodide ions. Through the response of luminescence color upon ion exchange, the ACD-PNCs can detect aqueous Cl− and I− with good selectivity and sensitivity. Under optimum conditions, the LOD and % RSD were determined as 3.2*10−6 M and 5.7% for Cl−, 9.0*10−6 M and 6.7% for I−, respectively. To identify halide ions in samples like sweat, saliva, and kelp, conveniently prepared ACD-PNCs test strips were employed. This work provides insights into the design and development of perovskite probes capable of detection in aqueous solution, and also demonstrates the importance of rapidly forming hydrogen-bonding networks when studying such sensing systems.

Serotonin is a gap junction-permeable neuronal tracer in the mouse retina.

Gap junctions are dynamically modulated bridges allowing the transcellular passage of ions and small molecules with a molecular mass of up to 1 kDa, a mechanism utilized for molecular communication purposes by living cells. This same mechanism is also exploited by scientists to reveal the existence of gap junction contacts by the cell-to-cell movement of tracers. However, multiple labeling experiments require the availability of multiple gap junction-permeable tracers. To this end, we utilized the well-known transient OFF alpha retinal ganglion cell (RGC)-coupled array as a model system to study and compare the transjunctional movement of neurobiotin (NB), a commonly used tracer, and serotonin, a recently identified tracer. Although the transjunctional movement of serotonin has been established in cell cultures, here we show, for the first time, that serotonin is also a potent tracer in in vitro tissue. In addition, serotonin is lighter than the classical gap junction-permeable NB, and thus, we expected that tracer movement would be comparable to or better than that of serotonin. We found that intracellular serotonin injections result in the labeling of the coupled transient OFF alpha RGC array very similar to those of the classical NB-labeled arrays. Both serotonin and NB-injected transient OFF alpha RGCs displayed the well-known pattern with coupled RGCs and a cohort of coupled wide-field amacrine cells (ACs). By using morphological characteristics, we confirm that the serotonin and the NB-coupled AC arrays are identical, and thereby confirm that serotonin is a potent gap junction-permeable tracer and can be readily used as an alternative to NB in in vitro tissue. Moreover, serotonin can be utilized in parallel with other dyes or tracers, enabling the use of multiple labels in the same material.

Ethanol effects on L-type voltage-gated calcium channel performance

Drinking too much alcohol can lead to the development of chronic diseases and other serious problems including: heart disease, high blood pressure, stroke, digestive problems and liver disease. Over the past two decades, researchers have confirmed that ethanol is the primary agent in altering the function of voltage-gated calcium channels that lead to clock responses and behavioral responses to alcohol. In this study, the ethanol influence on calcium channel operation has been studied by molecular dynamics simulation of L-type calcium channels in the presence and absence of ethanol. Density, radius distribution, average potential force, radius gyration, pore radius, root mean square deviation and root mean square fluctuation are the performed analysis in this study. According to the results obtained; Ethanol blocks the calcium channel and interferes with calcium ions passage. Also, calcium ions show a greater tendency to interact with the residues inside the protein channel in the presence of ethanol.

MOF 801(Ce)-modified polypropylene separator as efficient barrier for lithium–organosulfide batteries

Phenyl tetrasulfide (PTS) is a high-capacity cathode material for lithium batteries. However, it also suffers the shuttle effect of polysulfides to the lithium anode in the charge because some lithium polysulfides are still formed due to the middle sulfur atoms in the structure of PTS. The separator modification is considered as a convenient and effective strategy to reduce the shuttle effect. In this report, metal-organic framework (MOF)-801(Ce) is synthesized and coated on a polypropylene separator (MOF-801(Ce)−PP) as a polysulfide barrier. MOF-801(Ce) has a pore size of 6 Å, which is smaller than the sizes of lithium thiophenolate and lithium polysulfides. Therefore, the MOF-801(Ce)−PP can effectively inhibit the migration of active species to the lithium metal anode without affecting the passage of lithium ions. Consequently, the Li/PTS cell with the MOF-801(Ce)−PP exhibits a discharge capacity of 340.8 mAh g−1 at 0.5 C after 250 cycles, which is better than the control cell. Even when the PTS areal mass loading is 5.4 mg cm−2, the cell with the MOF-801(Ce)−PP can still deliver a high specific capacity of 430 mAh g−1 at 0.5 C rate. This study proves a feasible strategy to overcome the polysulfide shuttle issue of organosulfide cathode materials.

An efficient technique for the purification of fulvic acid extracted from leonardite

Fulvic acids (FAs) are significant natural organic compounds produced during the decomposition of plants and animals. There is great demand for FAs in pharmaceutical, cosmetic, and industrial applications. However, their use is declining due to the tedious purification process. This study developed a method to purify FAs extracted directly from leonardite-rich humic substances. The method introduces a permeation cell integrated with a polymer inclusion membrane to separate target impurities related to FAs from extractants and humic raw material sources. Polymeric membranes were prepared using fixed proportions of cellulose triacetate, tri octyl methylammonium chloride, tributyl phosphate, and 2-nitrophenyl pentyl ether. The purified fulvic acids, feed phase, and stripping phase products were characterized using SEM, EDX, FTIR, and UV-Vis. Fluorescence spectroscopy analysis was also performed to compare the purity intensity of fluorescence spectra of the respective components of the feed and stripping phase. In terms of purification, the membrane obstructed the passage of foreign ions and unwanted particles and allowed only FAs molecules to pass through. This research affirms that the present method is more effective, cheaper, and more convenient than the classical method for FAs purification.

Modelling of nanocrystalline insulators response to swift heavy ion irradiation

We apply a hybrid multiscale model to describe structural damage in nanocrystalline insulators irradiated with swift heavy ions. The approach couples Monte Carlo code TREKIS tracing excitation of the electron ensemble and energy transfer to target atoms with the molecular dynamics simulating the lattice kinetics during its relaxation. We compare response of amorphizable and non-amorphizable nanocrystalline targets to strong perturbations initiated by an ion impact. The recrystallization processes observed in non-amorphizable MgO and Al2O3 strongly affects the grain boundaries that may result in association and enlargement of nanoparticles. Strong material heating and expansion in the track core can form voids near the grain boundaries. In contrast, swift heavy ion passage in the amorphizable sample almost do not affect the grains morphology forming amorphous tracks, similarly to the damage in the bulk.

Graphene skeletal nanotemplate coordinated with pH-Responsive porous Double-Ligand Metal-Organic frameworks (DL-MOFs) through ligand exchange theory for High-Performance smart coatings

For the first time, thermally stable and high-performance pH-responsive anti-corrosive nanoreservoirs based on double-ligand zinc phosphate framework (ZPF) decorated graphene oxide skeletal template (G-ZPF) was prepared through the ligand exchange theory. The G-ZPF nanoreservoirs, and pristine materials were monitored by X-ray diffraction (XRD), Thermo gravimetric analysis (TGA), Field emission scanning electron microscopy (FE-SEM), Fourier transforms infrared (FT-IR) spectroscopy, and Brunauer-Emmett-Teller (BET) analyses. The outcomes revealed that a highly thermal stable double-ligand porous coordination polymer was synthesized properly. pH-responsive corrosion inhibitors release ability of G-ZPF nanoreservoirs was studied in the acidic, neutral, and alkaline saline (3.5 wt% concentration of NaCl) solutions, and the release rate of active corrosion inhibiting substances (Zinc and phosphate ions, and 2-methylimidazole molecules) was measured by inductively coupled plasma-optical emission spectrometry (ICP-OES), and total organic carbon (TOC) techniques. Electrochemical (polarization, and EIS), and surface analyses were conducted for investigating the G-ZPF nanoreservoirs corrosion inhibition ability in the saline solution, and mild steel samples coated with the epoxy-polyamide incorporated with G-ZPF nanoreservoirs in intact and scratched forms. The results showed that structural inhibitors-loaded G-ZPF nanoreservoirs guarantee both active (self-healing), and passive (ion- water barrier) characteristics of the organic coating. The results of Pull off, salt spray, cathodic disbonding, dynamic mechanical analysis (DMTA), and tensile tests showed robust corrosion prevention and excellent thermo/mechanical performance of the epoxy-polyamide coating loaded with G-ZPF nanoreservoirs.

Selectivity through ion modulated changes in pKa values.

In bacterial voltage gated sodium (Nav) channels, the passage of ions through the pore is controlled by a selectivity filter (SF) comprised of four glutamate residues. The mechanism of selectivity has been the subject of intense research, with suggested mechanisms based on steric effects, and ion triggered conformational change. Here we propose a novel mechanism based on ion-triggered shift in pKa values of SF glutamates. We study the NavMs channel for which the open channel structure is available. Our free energy calculations based on molecular dynamics simulations suggest that pKa values of the four glutamates are higher in solution of K+ ions, than in solution of Na+ ions. Since pKa values are close to the physiological pH, this results in predominant population of the fully deprotonated state of glutamates in Na+ solution, while protonated states are predominantly populated in K+ solution. Through molecular dynamics simulations we also calculate the conductances of the relevant protonation states. The deprotonated state is the most conductive, single protonated state is less conductive, and double protonated state has further reduced conductance. Thus, we propose that the selectivity is achieved through ion triggered shift in protonation state which favors more conductive states for Na+ ions and less conductive states for K+ ions. This mechanism would also suggest pH dependence of selectivity, which was experimentally observed in structurally similar NaChBas channels.

VDAC interactions with lipids and their effect on isoform specificity.

The Voltage-Dependent Anion Channel (VDAC) is a β-barrel, the most abundant protein of the mitochondrial outer membrane, allowing passage of ions and metabolites (such as ATP, ADP, NADH⋯) in and out of the mitochondria. Besides its transport function, VDAC is also implicated in mitochondrial regulation with roles in apoptosis, calcium homeostasis or neurodegeneration. However, its role in those different pathways remains to be understood at the molecular level. VDAC possesses 3 isoforms in mammals (VDAC1, 2 and 3), sharing a high sequence identity, the same architecture and an overlapping tissue distribution. They display very similar transport properties such as conductance, selectivity and voltage-induced closure while their isoform specificity originates from their different interaction with partner proteins. This may determine their unique role in mitochondrial regulation, where each isoform seems to have different functions and a different set of partners: VDAC1 is implicated in neurodegeneration (Alzheimer and Parkinson disease), VDAC2 in apoptosis and calcium homeostasis, and VDAC3 probably in spermatogenesis and oxidative stress. Using a combination of biochemistry, molecular dynamics and electrophysiology, we investigated the lipid organization around each VDAC isoform and their impact on VDAC function. Our data suggest that the three isoforms have different affinities for lipids, and that could contribute to the selection of interacting partners.

Tuning interactions in nanopore arrays with charges on the pore walls

Physiological processes at the cellular level are regulated by nanoconfined ionic transport. Protein channels regulate the passage of specific ions into and out of the cell, and biological systems rely on the concerted function of many channels embedded in their membranes. For instance, the propagation of an action potential down an axon is moderated by the coordinated transport of sodium and potassium ions across neuronal membranes. Beyond its ubiquity in biological systems, transport across nanoporous devices has industrial applications such as single-molecule sensing, energy storage, and water desalination. While single nanopore systems have been thoroughly studied in both biological and industrial contexts, systems containing an array of multiple nanopores are of increasing interest. Due to the close proximity of channels in an array, local environmental changes at the interface of one channel may influence the transport properties of neighboring channels. In this work, we fabricated nanopore arrays with tunable geometries and surface chemistries to probe this cross-talk between nanopores. We employed electron beam sculpting of silicon nitride membranes to fabricate arrays containing two and three nanopores. This method allowed us to engineer devices of varying interpore distances to probe neighboring interactions as a function of interpore distance. Using electrochemical methods, we characterized the current-voltage response of each array at varying sizes of the electric double layer to probe the nature of interpore interactions. Furthermore, we explored surface modifications to create nanopores with bipolar surface charge distributions, which effectively act as ionic diodes. Our results are also complemented by computational modeling. An exploration of the electrokinetic phenomena of these arrays will deepen our understanding of the interplay between neighboring channels, elucidating the mechanisms behind ionic sieving on the scale of an entire network of nanopores.

Amorphous Mixed-Vanadium-Tungsten Oxide Films as Optically Passive Ion Storage Materials for Solid-State Near-Infrared Electrochromic Devices.

Near infrared (NIR) electrochromic (EC) devices that selectively modulate the NIR light without affecting the daylight represent a promising window technology for saving energy consumption of buildings. Current research efforts have been focused on developing NIR-EC materials, while little attention has been directed to the optically passive ion storage materials that are crucial for balancing charges in a full NIR-EC device. Herein, we report that amorphous phase mixed-vanadium-tungsten oxide films exhibit minimum optical change with high ion storage capacity, which enables the usage of the mixed-metal oxides as optically passive counter electrode materials for NIR-EC devices. The mixed-vanadium-tungsten oxide films are synthesized by a room-temperature solution-based photodeposition method that allows us to precisely engineer the metal compositions and thicknesses of the mixed-metal oxide films, thus optimizing their optical inertness and ion storage capability. A solid-state NIR-EC device assembled with the mixed-vanadium-tungsten oxide film as an ion storage layer and the amorphous tungsten oxide hydrate as the NIR-EC layer shows fast response speed with cycling stability up to 10,000 cycles, proving the outstanding charge balancing capability of mixed-metal oxide. Our work provides an efficient strategy for developing optically passive ion storage films with high ion storage capability for high-performance EC devices.

Towards the maximization of nanochannels blockage through antibody-antigen charge control: Application for the detection of an Alzheimer’s disease biomarker

Although size and charge effects in nanochannels have been previously approached for electrochemical immunosensing, as far as we know, thorough studies on the effect of both the antibody and the antibody/antigen immunocomplex charges at different pHs have not been deeply reported. In this context, we present here an unprecedented study of such parameters, applied also for the first time for the detection of an Alzheimer’s disease (AD) biomarker. AD detection is currently based in time consuming and expensive techniques, so that the development of alternative analytical strategies for facilitating its diagnosis is still a need. To reach that purpose, we propose here the development of a nanochannel-based system for the electrochemical monitoring of Tau protein, an important AD biomarker. Tau protein is selectively captured by specific antibodies immobilized in the inner walls of the nanochannels of nanoporous alumina membranes. The captured Tau protein blocks the nanochannel and difficulties the passage of red-ox indicator ions, which is voltammetrically monitored using an indium tin oxide/poly(ethylene terephthalate) (ITO/PET) electrode as transducer. The charges of both the antibody and the Tau antigen at different pHs and their effect on the diffusion of the red-ox indicator ions to the electrode are carefully evaluated to maximize the electrostatic blocking of the nanochannels upon the immunocomplex formation. The developed biosensing system allows the determination of Tau protein with a detection limit of 4.3 ng/mL, which is within the range of clinical interest, showing also excellent recovery percentages in human plasma samples.