Theoretical Framework and Guidelines for the Cyclic Voltammetry of Closed Bipolar Cells.

Closed bipolar cells (cBPCs) can offer valuable platforms for the development of electrochemical sensors. On the other hand, such systems are more intricate to model and interpret than conventional systems with a single polarizable interface, with the applied potential "splitting" into two polarized interfaces where two coupled charge transfers take place concomitantly. As a result, the voltammetry of cBPCs shows peculiarities that can be misleading if analyzed under the framework of classic electrochemical cells. In this work, rigorous mathematical solutions are deduced for the cyclic voltammetry (CV) of cBPCs, including the current-potential response, the interfacial potentials, and the interfacial redox concentrations. With such theoretical tools, a comprehensive view of the behavior of cBPCs can be gained, and adequate diagnosis criteria are established on the basis of the shape, magnitude, and position of the CV signal as a function of the scan rate and of the experimental conditions in the anodic and cathodic compartments.

Voltammetric Kinetic Studies of Electrode Reactions: Guidelines for Detailed Understanding of Their Fundamentals.

Theoretical and practical foundations of basic electrochemical concepts of heterogeneous charge transfer reactions that underline electrochemical processes are presented for their detailed study by undergraduate and postgraduate students. Several simple methods for calculating key variables, such as the half-wave potential, limiting current, and those implied in the kinetics of the process, are explained, discussed, and put in practice through simulations making use of an Excel document. The current-potential response of electron transfer processes of any kinetics (i.e., any degree of reversibility) are deduced and compared for electrodes of different size, geometry, and dynamics, namely: static macroelectrodes in chronoamperometry and normal pulse voltammetry, and static ultramicroelectrodes and rotating disc electrodes in steady state voltammetry. In all cases, a universal, normalized current-potential response is obtained in the case of reversible (fast) electrode reactions, whereas this is not possible for nonreversible processes. For this last situation, different widely used protocols for the determination of the kinetic parameters (the mass-transport corrected Tafel analysis and the Koutecký-Levich plot) are deduced, proposing learning activities that highlight the foundations and limitations of such protocols, as well as the influence of the mass transport conditions. Discussions on the implementation of this framework and on the benefits and difficulties found are also presented.

Investigating Comproportionation in Multielectron Transfers via UV-Visible Spectroelectrochemistry: The Electroreduction of Anthraquinone-2-sulfonate in Aqueous Media.

UV-vis spectroelectrochemistry is assessed as a tool for the diagnosis and quantitative in situ investigation of the incidence of comproportionation in multielectron transfer processes. Thus, the sensitivity of the limiting current chronoabsorptometric signals related to the different redox states to the comproportionation kinetics is studied theoretically for different working modes (normal and parallel light beam arrangements) and mass transport regimes (from semi-infinite to thin layer diffusion). The theoretical results are applied to the spectroelectrochemical study of the two-electron reduction of the anthraquinone-2-sulfonate in alkaline aqueous solution, tuning the thermodynamic favorability of the comproportionation reaction through the electrolyte cation. The quantitative analysis of the experimental results reveals the occurrence of comproportionation in the three media examined, showing different kinetics depending on the cationic species in solution.

A PSMA-targeted bispecific antibody for prostate cancer driven by a small-molecule targeting ligand.

Despite the development of next-generation antiandrogens, metastatic castration-resistant prostate cancer (mCRPC) remains incurable. Here, we describe a unique semisynthetic bispecific antibody that uses site-specific unnatural amino acid conjugation to combine the potency of a T cell-recruiting anti-CD3 antibody with the specificity of an imaging ligand (DUPA) for prostate-specific membrane antigen. This format enabled optimization of structure and function to produce a candidate (CCW702) with specific, potent in vitro cytotoxicity and improved stability compared with a bispecific single-chain variable fragment format. In vivo, CCW702 eliminated C4-2 xenografts with as few as three weekly subcutaneous doses and prevented growth of PCSD1 patient-derived xenograft tumors in mice. In cynomolgus monkeys, CCW702 was well tolerated up to 34.1 mg/kg per dose, with near-complete subcutaneous bioavailability and a PK profile supporting testing of a weekly dosing regimen in patients. CCW702 is being evaluated in a first in-human clinical trial for men with mCRPC who had progressed on prior therapies (NCT04077021).

General Explicit Mathematical Solution for the Voltammetry of Nonunity Stoichiometry Electrode Reactions: Diagnosis Criteria in Cyclic Voltammetry.

Electrochemical reactions can effectively follow nonunity stoichiometries as can be found in the electrochemistry of halides, hydrogen, and metal complexes. The voltammetric response of these systems shows peculiar deviations with respect to the well-described features of the 1:1 stoichiometry. With the aim of specifying such differences, a rigorous and manageable analytical theory is deduced for the complete characterization of reversible electrode processes with complex stoichiometry in cyclic voltammetry (CV) at macroelectrodes. Particularly, the main features of the CV of 2:1, 1:2, 3:1, and 1:3 processes (that is, the peak currents and potentials and the influence of the scan rate and of the species concentration and diffusion coefficients) are given and compared with the 1:1 case in order to propose unambiguous diagnostic criteria of the stoichiometry of the electrode reaction. Also, expressions for the concentration profiles and surface concentrations of the redox species are given.

Asymmetric (ADMA) and Symmetric (SDMA) Dimethylarginines in Chronic Kidney Disease: A Clinical Approach.

Asymmetric dimethylarginine (ADMA) and its enantiomer, Symmetric dimethylarginine (SDMA), are naturally occurring amino acids that were first isolated and characterized in human urine in 1970. ADMA is the most potent endogenous inhibitor of nitric oxide synthase (NOS), with higher levels in patients with end-stage renal disease (ESRD). ADMA has shown to be a significant predictor of cardiovascular outcome and mortality among dialysis patients. On the other hand, although initially SDMA was thought to be an innocuous molecule, we now know that it is an outstanding marker of renal function both in human and in animal models, with ESRD patients on dialysis showing the highest SDMA levels. Today, we know that ADMA and SDMA are not only uremic toxins but also independent risk markers for mortality and cardiovascular disease (CVD). In this review, we summarize the role of both ADMA and SDMA in chronic kidney disease along with other cardiovascular risk factors.

Impact of a phone app on nephrology referral.

BACKGROUND: Various factors can lead to inadequate nephrology referral decisions being taken by clinicians, but a major cause is unawareness of guidelines, recommendations and indications, or of appropriate timing. Today, tools such as smartphone applications (Apps) can make this knowledge more accessible to non-nephrologist clinicians. Our study aim is to determine the effectiveness of a purpose-built app in this respect. METHODS: In a retrospective study, nephrology referrals were compared before and after the introduction of the app in clinical practice. The initial study population consisted of first visits by patients referred to our department in 2015, before the introduction of the app. In 2016, the smartphone app NefroConsultor began to be implemented in our hospital. We compared the initial study population with the results obtained for patients referred in 2017, when the app was in use, taking into account clinical features considered, such as urinalysis, proteinuria or kidney ultrasound, to determine whether these patients met currently recommended criteria for referral. RESULTS: The total study population consisted of 628 patients, of whom 333 were examined before the introduction of the app (in 2015) and 295 when it was in use (in 2017). Among the first group, 132 (39.6%) met established KDIGO criteria for nephrology referral and were considered to be correctly referred. Among the second group, 200 (67.8%) met the criteria and were considered to be properly referred (P = 0.001). The increase in the rate of intervention success (before-after app) was 28.8% with a binomial effect size display (Cohen's d effect size) of 0.751. Before the introduction of the app, data for albuminuria were included in 62.5% of nephrology referrals; in 2017, the corresponding value was 87.5% (P = 0.001). In the same line, referrals including urinalysis rose from 68.5% to 85.8% (P = 0.001). Multivariate regression analysis, using referrals meeting KDIGO criteria as the dependent variable and adjusting for age, sex and referring department, showed that the 2017 group (after the introduction of NefroConsultor) was associated with an odds ratio of 3.57 (95% confidence interval 2.52-5.05) for correct referrals, compared with the 2015 group (P = 0.001). References to proteinuria as the reason for nephrology referral also increased from 23.7% to 34.2% (P = 0.004). CONCLUSIONS: Use of the app is associated with more frequent studies of albuminuria at the time of referral and a greater likelihood of proteinuria being cited as the reason for referral. The smartphone app considered can improve the accessibility of information concerning nephrology referrals and related studies.

Guidelines for the Voltammetric Study of Electrode Reactions with Coupled Chemical Kinetics at an Arbitrary Electrode Geometry.

A powerful, unified, and simplifying mathematical approach for the theoretical treatment of first-order chemical kinetics coupled to interfacial charge transfers at electrodes of arbitrary geometry and size, both uniformly accessible and nonuniformly accessible to the electroactive species, is presented. The general CEC mechanism at spherical and disc electrodes is considered to test the validity and benefits of such an approach, based on the application of the so-called kinetic steady state, that enables the reduction of the multivariable problem of kinetic-diffusive differential equations to a single variable problem of a diffusion-only differential equation. This is solved both analytically and numerically, showing how this approach leads to general, simple, and efficient solutions for the study of the influence of coupled chemical kinetics on the voltammetric response. The voltammetry of the CEC mechanism is analyzed as a function of the kinetics and thermodynamics of the preceding and subsequent chemical reactions and of the electrode size (from macroelectrodes to ultramicroelectrodes) and shape (spherical and disc). Comparison with the responses of the CE, EC, and E mechanisms is included, proposing diagnosis criteria and procedures for quantitative analysis of experimental data.

Fluctuation of pre-hemodialysis serum sodium
.

INTRODUCTION: Low pre-hemodialysis (pre-HD) serum sodium or hyponatremia is associated with higher mortality. Pre-HD serum sodium can be more stable over time with low fluctuation compared to other serum parameters. MATERIALS AND METHODS: We examined variation of pre-HD serum sodium in 24 months and after this point examined all-cause mortality in a cohort of 261 patients followed-up for 48.8 (standard deviation (SD) = 19.1) months. 6,221 determinations of pre-HD serum sodium were made and corrected for glucose concentrations. Serum sodium was measured pre-HD monthly, and the variability was calculated using the coefficient of variation (CV). RESULTS: The mean age was of 60 ± 14.1 years, 60.9% were men, 48% had diabetes mellitus, and diabetic nephropathy was the most frequent cause of end-stage renal disease. Median CV of sodium in 24 months was 1.7% with a mean of 1.78% (95% CI 1.73 - 1.83). Patients with CV > 1.7% had a higher mortality (53 patients a 36.8%) compared to CV < 1.7% (22 patients a 18.8%) (p = 0.002). In Kaplan-Meier analysis, patients with CV > 1.7% had significantly worse overall survival (log rank = 6.395, p = 0.011). We also stratified the sample in serum sodium tertiles (< 138 mEq/L; 138 - 140 mEq/L; > 140 mEq/L) and made a Kaplan-Meier analysis which showed persistent worse survival outcomes in patients with CV > 1.7% (log rank Mantel-Cox 7.64; p = 0.006). Cox regression multivariate model showed that CV of sodium was significantly associated with overall mortality after adjusting for confounder variables (hazard ratio 2.16, 95% CI 1.37 - 3.41; p = 0.001). CONCLUSION: Variation of pre-HD serum sodium in 2 years is less than a 2%. With the limitations of our study, a higher variability of pre-HD serum sodium in 2 years of treatment (CV > 1.7%) is associated with increased mortality.
.

Remission of Spontaneous Canine Tumors after Systemic Cellular Viroimmunotherapy.

Dogs with spontaneous tumors treated in veterinary hospitals offer an excellent opportunity for studying immunotherapies, including oncolytic viruses. Oncolytic viruses have advanced into the clinic as an intratumorally administered therapeutic; however, intravenous delivery has been hindered by neutralization in the blood. To circumvent this hurdle, mesenchymal stem cells have been used as a "Trojan horse." Here, we present the treatment of 27 canine patients with cancer with canine mesenchymal stem cells infected with ICOCAV17, a canine oncolytic adenovirus. No significant adverse effects were found. The response rate was 74%, with 14.8% showing complete responses, including total remissions of lung metastasis. We detected virus infection, stromal degeneration, and immune cell infiltration in tumor biopsies after 4 weeks of treatment. The increased presence of antiadenoviral antibodies in the peripheral blood of treated dogs did not appear to prevent the clinical benefit of this therapy. These data indicate that oncolytic viruses loaded in mesenchymal stem cells represent an effective cancer immunotherapy.Significance: The classical clinical limitations of antitumoral viroimmunotherapy can be overcome by use of mesenchymal stem cells.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/17/4891/F1.large.jpg Cancer Res; 78(17); 4891-901. ©2018 AACR.

Double Transfer Voltammetry in Two-Polarizable Interface Systems: Effects of the Lipophilicity and Charge of the Target and Compensating Ions.

Analytical expressions are obtained for the study of the net current and individual fluxes across macro- and micro-liquid/liquid interfaces in series as those found in ion sensing with solvent polymeric membranes and in ion-transfer batteries. The mathematical solutions deduced are applicable to any voltammetric technique, independently of the lipophilicity and charge number of the target and compensating ions. When supporting electrolytes of semihydrophilic ions are employed, the so-called double transfer voltammograms have a tendency to merge into a single signal, which complicates notably the modeling and analysis of the electrochemical response. The present theoretical results point out that the appearance of one or two voltammetric waves is highly dependent on the size of the interfaces and on the viscosity of the organic solution. Hence, the two latter can be adjusted experimentally in order to "split" the voltammograms and extract information about the ions involved. This has been illustrated in this work with the experimental study in water | 1,2-dichloroethane | water cells of the transfer of the monovalent tetraethylammonium cation compensated by anions of different lipophilicity, and also of the divalent hexachloroplatinate anion.

Theoretical Treatment of Ion Transfers in Two Polarizable Interface Systems When the Analyte Has Access to Both Interfaces.

A new theory is presented to tackle the study of transfer processes of hydrophilic ions in two polarizable interface systems when the analyte is initially present in both aqueous phases. The treatment is applied to macrointerfaces (linear diffusion) and microholes (highly convergent diffusion), obtaining analytical equations for the current response in any voltammetric technique. The novel equations predict two signals in the current-potential curves that are symmetric when the compositions of the aqueous phases are identical while asymmetries appear otherwise. The theoretical results show good agreement with the experimental behavior of the "double transfer voltammograms" reported by Dryfe et al. in cyclic voltammetry (CV) ( Anal. Chem. 2014 , 86 , 435 - 442 ) as well as with cyclic square wave voltammetry (cSWV) experiments performed in the current work. The theoretical treatment is also extended to the situation where the target ion is lipophilic and initially present in the organic phase. The theory predicts an opposite effect of the lipophilicity of the ion on the shape of the voltammograms, which is validated experimentally via both CV and cSWV. For the above two cases, simple and manageable expressions and diagnosis criteria are derived for the qualitative and quantitative study of ion lipophilicity. The ion-transfer potentials can be easily quantified from the separation between the two signals making use of explicit analytical equations.

Electrochemical and Electrostatic Cleavage of Alkoxyamines.

Alkoxyamines are heat-labile molecules, widely used as an in situ source of nitroxides in polymer and materials sciences. Here we show that the one-electron oxidation of an alkoxyamine leads to a cation radical intermediate that even at room temperature rapidly fragments, releasing a nitroxide and carbocation. Digital simulations of experimental voltammetry and current-time transients suggest that the unimolecular decomposition which yields the "unmasked" nitroxide (TEMPO) is exceedingly rapid and irreversible. High-level quantum computations indicate that the collapse of the alkoxyamine cation radical is likely to yield a neutral nitroxide radical and a secondary phenylethyl cation. However, this fragmentation is predicted to be slow and energetically very unfavorable. To attain qualitative agreement between the experimental kinetics and computational modeling for this fragmentation step, the explicit electrostatic environment within the double layer must be accounted for. Single-molecule break-junction experiments in a scanning tunneling microscope using solvent of low dielectric (STM-BJ technique) corroborate the role played by electrostatic forces on the lysis of the alkoxyamine C-ON bond. This work highlights the electrostatic aspects played by charged species in a chemical step that follows an electrochemical reaction, defines the magnitude of this catalytic effect by looking at an independent electrical technique in non-electrolyte systems (STM-BJ), and suggests a redox on/off switch to guide the cleavage of alkoxyamines at an electrified interface.

Development of A Chimeric Antigen Receptor Targeting C-Type Lectin-Like Molecule-1 for Human Acute Myeloid Leukemia.

The treatment of patients with acute myeloid leukemia (AML) with targeted immunotherapy is challenged by the heterogeneity of the disease and a lack of tumor-exclusive antigens. Conventional immunotherapy targets for AML such as CD33 and CD123 have been proposed as targets for chimeric antigen receptor (CAR)-engineered T-cells (CAR-T-cells), a therapy that has been highly successful in the treatment of B-cell leukemia and lymphoma. However, CD33 and CD123 are present on hematopoietic stem cells, and targeting with CAR-T-cells has the potential to elicit long-term myelosuppression. C-type lectin-like molecule-1 (CLL1 or CLEC12A) is a myeloid lineage antigen that is expressed by malignant cells in more than 90% of AML patients. CLL1 is not expressed by healthy Hematopoietic Stem Cells (HSCs), and is therefore a promising target for CAR-T-cell therapy. Here, we describe the development and optimization of an anti-CLL1 CAR-T-cell with potent activity on both AML cell lines and primary patient-derived AML blasts in vitro while sparing healthy HSCs. Furthermore, in a disseminated mouse xenograft model using the CLL1-positive HL60 cell line, these CAR-T-cells completely eradicated tumor, thus supporting CLL1 as a promising target for CAR-T-cells to treat AML while limiting myelosuppressive toxicity.

Aqueous Voltammetry in the Near Absence of Electrolyte.

In order to minimize the incidence of the CO2 hydrolysis and conduct aqueous electrochemistry in the virtual absence of electrolyte, a novel methodology is developed to achieve the near minimum conductivity (≈60 nS cm-1 ) for an aqueous solution through in situ deionization with ion exchange resin beads. Aqueous electrochemistry studying the oxidations of platinum, ferrocenemethanol, and hydrogen (H2 ) were conducted in the near complete absence of trace ionic species at a platinum microelectrode (d=10 µm). Both surface and solution phase electrochemical reactions were clearly observed, indicating that under these conditions there is a sufficiently compressed double layer for an interfacial electron transfer to be driven and the iR effects are significantly smaller than theoretically expected.

Microelectrode voltammetry of multi-electron transfers complicated by coupled chemical equilibria: a general theory for the extended square scheme.

A very general and simple theoretical solution is presented for the current-potential-time response of reversible multi-electron transfer processes complicated by homogeneous chemical equilibria (the so-called extended square scheme). The expressions presented here are applicable regardless of the number of electrons transferred and coupled chemical processes, and they are particularized for a wide variety of microelectrode geometries. The voltammetric response of very different systems presenting multi-electron transfers is considered for the most widely-used techniques (namely, cyclic voltammetry, square wave voltammetry, differential pulse voltammetry and steady state voltammetry), studying the influence of the microelectrode geometry and the number and thermodynamics of the (electro)chemical steps. Most appropriate techniques and procedures for the determination of the 'interaction' between successive transfers are discussed. Special attention is paid to those situations where homogeneous chemical processes, such as protonation, complexation or ion association, affect the electrochemical behaviour of the system by different stabilization of the oxidation states.

Electrochemistry of single droplets of inverse (water-in-oil) emulsions.

We demonstrate the feasibility of electrochemically detecting individual water droplets dispersed in an oil phase (inverse emulsions) via the use of a redox probe confined in the droplet phase. The water droplets were tagged with potassium ferrocyanide, and were injected into an electrolyte cyclohexene/dichloromethane oil solution. Via simple cyclic voltammetry scans it is shown that single water droplets from a water-in-oil emulsion can be detected provided that rapid anion transfer from the oil to the water phase maintains electro-neutrality in the droplet.

Characterization of inclusion complexes of organic ions with hydrophilic hosts by ion transfer voltammetry with solvent polymeric membranes.

The quantitative characterization of inclusion complexes formed in aqueous phase between organic ions and hydrophilic hosts by ion-transfer voltammetry with solvent polymeric membrane ion sensors is studied, both in a theoretical and experimental way. Simple analytical solutions are presented for the determination of the binding constant of the complex from the variation with the host concentration of the electrochemical signal. These solutions are valid for any voltammetric technique and for solvent polymeric membrane ion sensors comprising one polarisable interface (1PI) and also, for the first time, two polarisable interfaces (2PIs). Suitable experimental conditions and data analysis procedures are discussed and applied to the study of the interactions of a common ionic liquid cation (1-octyl-3-metyl-imidazolium) and an ionisable drug (clomipramine) with two hydrophilic cyclodextrins: α-cyclodextrin and 2-hydroxypropyl-ß-cyclodextrin. The experimental study is performed via square wave voltammetry with 2PIs and 1PI solvent polymeric membranes and in both cases the electrochemical experiments enable the detection of inclusion complexes and the determination of the corresponding binding constant.

Single Fusion Events at Polarized Liquid-Liquid Interfaces.

A new electrochemical framework for tracking individual soft particles in solution and monitoring their fusion with polarized liquid-liquid interfaces is reported. The physicochemical principle lies in the interfacial transfer of an ionic probe confined in the particles dispersed in solution and that is released upon their collision and fusion with the fluid interface. As a proof-of-concept, spike-like transients of a stochastic nature are reported in the current-time response of 1,2-dichloroethane(DCE)|water(W) submilli-interfaces after injection of DCE-in-W emulsions. The sign and potential dependence of the spikes reflect the charge and lipophilicity of the ionic load of the droplets. A comparison with dynamic light scattering measurements indicates that each spike is associated with the collision of a single sub-picoliter droplet. This opens a new framework for the study of single fusion events at the micro- and nanoscale and of ion transport across biomimetic soft interfaces.

Voltammetry of the aqueous complexation-dissociation coupled to transfer (ACDT) mechanism with charged ligands.

The study of the so-called aqueous complexation-dissociation coupled to transfer (ACDT) mechanism is extended to systems where the ligand species is not neutral and so the charge of the two transferable ions is different (z1 ≠ z2). This has a profound effect on the voltammetric response of the system, which shows a complex behaviour depending on the chemical kinetics, the difference between the lipophilicity of the two ions and the applied potential. Such response is modelled making use of the diffusive-kinetic steady state (dkss) approach, obtaining analytical expressions for the current-potential-time curves in normal pulse, derivative and differential multipulse voltammetries. In addition, manageable expressions for the concentration profiles, interfacial fluxes and interfacial concentrations of all the species either side of the liquid|liquid interface are derived. From them, the effect on the voltammograms of the characteristics of the chemical reaction and the lipophilicity of the ions is thoroughly studied, comparing the cases where the ions carry the same and a different charge. The last case shows some striking behaviours that can be understood from the analysis of the concentration profiles.