Complex Redox Research Articles

Disulfide based prodrugs for cancer therapy.

Advances in the tumor microenvironment have facilitated the development of novel anticancer drugs and delivery vehicles for improved therapeutic efficacy and decreased side effects. Disulfide bonds with unique chemical and biophysical properties can be used as cleavable linkers for the delivery of chemotherapeutic drugs. Accordingly, small molecule-, peptide-, polymer- and protein-based multifunctional prodrugs bearing cleavable disulfide bonds are well accepted in clinical settings. Herein, we first briefly introduce a number of prodrugs and divide them into three categories, namely, disulfide-containing small molecule conjugates, disulfide-containing cytotoxic agent–targeted fluorescent agent conjugates, and disulfide-containing cytotoxic agent–macromolecule conjugates. Then, we discuss the complex redox environment and the underlying mechanism of free drug release from disulfide based prodrugs in in vivo settings. Based on these insights, we analyze the impact of electronics, steric hindrance and substituent position of the disulfide linker on the extracellular stability and intracellular cleavage rate of disulfide containing prodrugs. Current challenges and future opportunities for the disulfide linker are provided at the end.

MnI complex redox potential tunability by remote lewis acid interaction.

In this work we provide direct experimental evidence on the correlation of remote interactions between a newly synthesized MnI-complex (1) and different alkali cations with redox potential tuning. Furthermore we report the electrochemical behavior of 1 towards carbon dioxide, including the effects of added alkali salts using cyclic voltammetry.

Correlation of electrochemical and ab initio investigations of iron poly-bipyridine coordination complexes for battery applications: impact of the anionic environment and the local geometries of the redox complexes on the electrochemical response.

Although they exhibit huge versatility, coordination complexes have been rarely investigated in the field of cathode materials for batteries. Despite their relatively high molecular mass, according to the nature of the metallic center and that of the ligand, the E° value and the electron transfer kinetics can be adjusted to develop a performant material compatible with the electrolyte. Here, we propose to investigate FeII poly-bipyridine complexes with a view to check the impact of the nature of the electrolyte as well as the influence of the distance between two redox centers when polymerized on the electrochemical response in battery conditions. To understand these changes, three lithium salts have been studied: LiClO4, LiPF6 and LiTFSI (TFSI = bis(trifluoromethane)sulfonimide). In order to mimic these impacts, monomer complexes (mono- and binuclear) have been electrochemically studied, whereas, thanks to ab initio calculations, their redox behavior has been correlated to the ligand environment of the metallic center. Finally, despite their expected low mass capacity, these polymeric coordination complexes have been involved in battery conditions.

Quantification of Anionic Redox Chemistry in a Prototype Na-Rich Layered Oxide.

Harnessing anionic redox reactions is of prime importance for boosting the capacity of sodium-ion batteries (NIBs). However, quantifying the cyclability of anionic redox reactions is still challenging. Herein, we conduct a qualitative and quantitative investigation of the cationic and anionic redox reactions of a prototype Na-rich layered oxide, namely, Na3RuO4, by a combination of bulk-sensitive X-ray absorption spectroscopy and full-range mapping of resonant inelastic X-ray scattering. We unequivocally reveal that both Ru cations and oxygen anions are involved in the charge compensation process of Na3RuO4. Ru redox is highly reversible over extended electrochemical cycles, while the cyclability of lattice oxygen redox gradually decreases with the retention of only 36% after 30 cycles, which is mainly responsible for the capacity fading of Na3RuO4. Our findings provide deeper insights into the complex oxygen redox mechanism, which plays a decisive role for designing high-energy Na-rich electrode materials for NIBs.

Application of DPPH Assay for Assessment of Particulate Matter Reducing Properties

Different acellular assays were developed to measure particulate matter’s (PM) oxidative potential (OP), a metric used to predict the ability of PM in generating oxidative stress in living organisms. However, there are still fundamental open issues regarding the complex redox equilibria among the involved species which could include reducing compounds. The aim of this study was the pilot application of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay to PM in order to evaluate the presence of reducing species. The assay, commonly applied to biological matrices, was adapted to PM and showed good analytical performances. It allowed the analysis of conventional 24 h airborne PM samples with suitable sensitivity and good repeatability of the measurements. The assay was applied to seven samples representing possible PM contributes (certified urban dust NIST1648a; brake dust; Saharan dust; coke dust; calcitic soil dust; incinerator dust; and diesel particulate matter certified material NIST1650b) and to PM2.5 field filters. The same samples were also analyzed for elements. Preliminary results indicated that the assay gave a linear response and that detectable amounts of reducing species were present in PM samples. The combined application of DPPH and conventional OP assays could then permit, in the future, to gain more knowledge about the reaction and/or competition between oxidative and reducing processes.

(Hydr)oxo-bridged heme complexes: From structure to reactivity

Iron–porphyrins ([Formula: see text] hemes) are present throughout the biosphere and perform a wide range of functions, particularly those that involve complex multiple-electron redox processes. Some common heme enzymes involved in these processes include cytochrome P450, heme/copper oxidase or heme/non-heme diiron nitric oxide reductase. Consequently, the (hydr)oxo-bridged heme species have been studied for the important roles that they play in many life processes or for their application for catalysis and preparation of new functional materials. This review encompasses important synthetic, structural and reactivity aspects of the (hydr)oxo-bridged heme constructs that govern their function and application. The properties and reactivity of the bridging (hydr)oxo moieties are directly dictated by the coordination environment of the heme core, the nature and ligation of the second metal center attached to the (hydr)oxo group, the presence or absence of a linker, and the degree of flexibility around that linker within the scaffold. Here, we summarize the structural features of all known (hydr)oxo-bridged heme constructs and use those to categorize and thus, provide a more comprehensive picture of structure–function relationships.

New application of microbial fuel cell-based biosensor for monitoring the quality of actual potato chips’ processing wastewater

In this study, a dual-chamber microbial fuel cell (MFC) fed with actual potato chips’ processing wastewater (PCPW) was tested as a biosensor. The performance of MFC-based biosensor was evaluated in terms of the current measurement range, toxicity detection and sensitivity, and the operational stability. The results revealed that the MFC can simply be converted to an online biosensor unit to detect the harmful effect of suspended solids and acidic content in the actual PCPW on the anodic attached biofilm and the values of the generated current as well. A notable decrease in the current values was observed indicating the adverse effects of the harmful matters in the PCPW fed to the biosensor unit. The results proposed a competition between the harmful components and the favorable substrate in binding to the redox complex. An excellent fitting was obtained between the experimental and predicted results by $$ I_{{K_{m} }} $$ model with determination coefficient (R2) and mean-square-error values of 0.927 and 0.363, respectively. Additionally, a new approach was developed based on direct measurement of actual field data to replace the conventional statistical methods.

Analysis of Arabidopsis thaliana Redox Gene Network Indicates Evolutionary Expansion of Class III Peroxidase in Plants

Reactive oxygen species (ROS) are byproducts of aerobic metabolism and may cause oxidative damage to biomolecules. Plants have a complex redox system, involving enzymatic and non-enzymatic compounds. The evolutionary origin of enzymatic antioxidant defense in plants is yet unclear. Here, we describe the redox gene network for A. thaliana and investigate the evolutionary origin of this network. We gathered from public repositories 246 A. thaliana genes directly involved with ROS metabolism and proposed an A. thaliana redox gene network. Using orthology information of 238 Eukaryotes from STRINGdb, we inferred the evolutionary root of each gene to reconstruct the evolutionary history of A. thaliana antioxidant gene network. We found two interconnected clusters: one formed by SOD-related, Thiol-redox, peroxidases, and other oxido-reductase; and the other formed entirely by class III peroxidases. Each cluster emerged in different periods of evolution: the cluster formed by SOD-related, Thiol-redox, peroxidases, and other oxido-reductase emerged before opisthokonta-plant divergence; the cluster composed by class III peroxidases emerged after opisthokonta-plant divergence and therefore contained the most recent network components. According to our results, class III peroxidases are in expansion throughout plant evolution, with new orthologs emerging in each evaluated plant clade divergence.

Coordination Complex Formation and Redox Properties of Kynurenic and Xanthurenic Acid Can Affect Brain Tissue Homeodynamics.

Reactive oxygen species (ROS) are known for their participation in various physiological and pathological processes in organisms, including ageing or degeneration. Kynurenine pathway metabolites, such as kynurenic (KYNA) or xanthurenic (XA) acid, can affect neurodegenerative diseases due to their ROS scavenging and Fe ion coordination complex formation but insights are still incomplete. Therefore, we investigated the formation and antioxidant capabilities of KYNA– and XA–Fe complexes by nano-electrospray−mass spectrometry, differential pulse voltammetry, deoxyribose degradation and FeII autoxidation assays. XA formed coordination complexes with FeII or FeIII ions and was an effective antioxidant. By contrast, only FeII–KYNA complexes could be detected. Moreover, KYNA showed no antioxidant effects in the FeCl3/ascorbic acid deoxyribose degradation assay variant and only negligible activities in the FeII autoxidation assay. Coordination complexes of Fe ions with KYNA probably stabilize KYNA in its keto tautomer form. Nevertheless, both KYNA and XA exhibited sufficient antioxidant activities in some of the employed assay variants. The results provide evidence that both have the potential to alleviate neurodegenerative diseases by helping to maintain tissue redox homeodynamics.

Fast repetition rate fs pulsed lasers for advanced PLIM microscopy

Simultaneous metabolic and oxygen imaging is promising to follow up therapy response, disease development and to determine prognostic factors. FLIM of metabolic coenzymes is now widely accepted to be the most reliable method to determine cellular bioenergetics. Also, oxygen consumption has to be taken into account to understand treatment responses. The phosphorescence lifetime of oxygen sensors is able to indicate local oxygen changes. For phosphorescence lifetime imaging (PLIM) dyes based on ruthenium (II) coordination complexes are useful, in detail TLD1433 which possesses a variety of different triplet states, enables complex photochemistry and redox reactions. PLIM is usually reached by two photon excitation of the drug with a femtosecond (fs) pulsed Ti:Sapphire laser working at 80[Formula: see text]MHz repetition rate and (time-correlated single photon counting) (TCSPC) detection electronics. The interesting question was whether it is possible to follow up PLIM using faster repetition rates. Faster repetition rates could be advantageous for the induction of specific photochemical reactions because of similar light doses used normally in standard CW light treatments. For this, a default 2[Formula: see text]-FLIM–PLIM system was expanded by adding a second fs pulsed laser (“helixx”) which provides 50[Formula: see text]fs pulses at a repetition rate of 250[Formula: see text]MHz, more than 2.3[Formula: see text]W average power and tunable from 720[Formula: see text]nm to 920[Formula: see text]nm. The laser beam was coupled into the AOM instead of the default 80[Formula: see text]MHz laser. We demonstrated successful applications of the 250[Formula: see text]MHz laser for PLIM which correlates well with measurements done by excitation with the conventional 80[Formula: see text]MHz laser source.

Redox states of nickel in zeolites and molecular account into binding of N2 to nickel(I) centers – IR, EPR and DFT study

Redox chemistry of nickel centers in high-silica ZSM-5 and BEA zeolites was investigated by a combined use of temperature-programmed reduction (TPR), electron paramagnetic resonance (EPR), and infrared (FTIR) spectroscopic techniques supported by quantum chemistry methods. The isolated nickel and nickel-oxo centers were identified and quantified by means of EPR using CO and NO probes and by IR using CO as a probe molecule. The nickel-oxo species gave rise to the nickel(I) centers upon reduction in CO. Their interaction with N 2 under low temperature led to the formation of nickel(I)–dinitrogen adducts. Attribution of the IR bands and identification of the structures of dinitrogen adducts were based on the coadsorption experiments of 14 N 2 and 15 N 2 isotopes and complementary density functional theory (DFT) calculations. Because of the presence of a mixed ligand ( 14 N 2 15 N 2 ) adduct, a structural dichotomy of possible formation of the geminal Ni(I)–(N 2 ) 2 and two coupled vicinal mono-adducts N 2 –Ni(I)⋅⋅⋅Ni(I)–N 2 was resolved. The isolated Ni(I)–N 2 and geminal Ni(I)–(N 2 ) 2 adducts were identified with confidence. A mechanism of N 2 bonding was accounted for by natural orbitals for chemical valence (NOCV) population analysis. Charge flow molecular channels due to the σ donation and π back-donation effects were established in a quantitative way. This allowed for unraveling the molecular background of the observed bathochromic shift of the stretching vibrations of all dinitrogen adducts. • Ni(II)-oxo and isolated Ni(I/II) centers undergo complex redox changes in zeolites. • Nickel speciation is controlled with protic/aprotic solution during ion exchange. • Nickel(I) forms isolated Ni(I)–N 2 and geminal Ni(I)–(N 2 ) 2 adducts. • Binding mechanism of N 2 by Ni(I) unraveled with charge flow σ and π channels.

A Versatile Pyramidal Hauerite Anode in Congeniality Diglyme‐Based Electrolytes for Boosting Performance of Li‐ and Na‐Ion Batteries

AbstractFor the first time, environmentally friendly sulfur‐rich pyramidal MnS2 synthesized via a single‐step hydrothermal process is used as a high‐performance anode material in Li‐ion and Na‐ion batteries. The superior electrochemical performance of the MnS2 electrode along with its high compatibility with ether‐based electrolytes are analyzed in both half‐ and full‐cell configurations. The reversible capacities of ≈84 mAh g−1 and ≈74 mAh g−1 at a current density of 50 mA g−1 are retained in the Li‐ion and Na‐ion full‐cells, respectively, over 200 cycles with excellent capacity retentions. Moreover, important findings regarding activation processes in the presence of a new phase transition and protective electrolyte interphase layer are revealed using ab initio density function theory calculation and in situ potentio‐electrochemical impedance spectroscopy. The detailed complex redox mechanism of MnS2 in Li/Na half‐cells is also elucidated by ex situ X‐ray photoelectron spectroscopy.

The nitrogen removal and sludge reduction performance of a multi-stage anoxic/oxic (A/O) biofilm reactor.

To overcome the problems of high excess sludge yield and poor nitrogen removal efficiency in traditional biological treatment processes, a multi-stage A/O biofilm reactor was developed by combining the multi-stage A/O process with novel floating spherical carriers, resulting in repeated coupling of anoxic and aerobic environments. Results showed that the system achieved COD, , and TN removal efficiencies of 93.8%, 84.5%, and 75.7%, respectively, with average effluent concentrations lower than: 29.8CODmg/L, 4.3 mg/L, and 13.2TNmg/L. The observed sludge yield was 0.139g MLSS/g COD, which was lower than that of the conventional activated sludge process. Microbial analysis showed that the community structure and cell morphology of microorganisms changed greatly with alternating aerobic-anoxic condition; high-throughput sequencing results proved that functional microorganisms can be enriched on the surface of the carries and therefore improved the nitrogen removal efficiency and meanwhile minimize the sludge yield within the system. PRACTITIONER POINTS: The research innovatively developed a novel floating spherical carrier and coupled it with multi-stage A/O process. The complex redox environments inside the floating spherical carriers improves the nitrogen removal efficiency and the sludge reduction effect. Nitrospirae, Hydrogenophaga promoted the nitrogen removal, Firmicutes, Bacteroidetes and Dechloromonas promoted the in-situ sludge reduction of the system.

Nanostructured MgFe and CoCr layered double hydroxides for removal and sequestration of iodine anions

Radioactive iodine-129 (129I) is a contaminant of concern at radiological waste disposal and nuclear power production sites where it can incidentally be released into the environment and migrate to groundwater. Development of remediation options for 129I is hindered by its complex and mobile redox speciation. In this work, we systematically evaluated nanostructured layered double hydroxide (LDH) materials comprised of MgFe or CoCr with variable M2+:M3+ molar ratios for their affinity for the environmentally-relevant anions of iodine including iodide (I−) and iodate (IO3−). Uncalcined MgFe material demonstrated overall poor selectivity, however, affinity for I− significantly increased with increasing Mg:Fe molar ratio and upon calcination due to elimination of the parent anions followed by reconstruction of the original LDH structure, assuming physisorption. Specific surface area of calcined MgFe before and after I− sorption showed 44.3 and 13.2 m2 g−1, respectively, indicating significant decrease by reconstruction effect. In addition, high sorption capacity of calcined MgFe for I− at about 2.5 mmol g−1 suggests its applicability for immobilization of 129I. On the other hand, uncalcined CoCr material exhibited high selectivity, affinity, and capacity (about 2 mmol g−1) for IO3− indicating chemisorption and its utility for treatments of 129I in groundwater. There was a minor specific surface area variation of uncalcined CoCr before and after IO3− sorption by ion exchange (53.2 and 64.0 m2 g−1, respectively). Overall this study provides mechanistic insights into understanding and prediction of behavior of the LDH materials as efficient sorbent for design of remedial option for 129I.

3D characterization of the subsurface redox architecture in complex geological settings

Nitrogen (N) leaching caused by agricultural activities is one of the major threats to the aquatic ecosystems and public health. Moving from the agricultural soils through the subsurface and reemerging to the surface water, N undergoes various biogeochemical reactions along pathways in the subsurface, which occur heterogeneously in space and time. Thus to improve our understanding on the fate and distribution of N in the aquatic environment, detailed knowledge about the subsurface hydrogeological and biogeochemical conditions, especially the redox conditions, are essential. In this study, 3D information of the redox conditions termed the redox architecture was investigated in two Danish catchments with intensive agriculture underlain by glacial deposits. Towed transient electromagnetic (tTEM) resistivity was interpreted which reveals the subsurface geological structures at a few hectare scale. These geophysical data were integrated with sediment and water chemistry for the redox architecture interpretations. The top soils of both catchments are characterized as clay-till, but the tTEM showed that the subsurface hydrogeological structures are distinctively different. We identified three types of redox architectures in the studied catchments: 1) a planar redox architecture with a single redox interface; 2) a geological-window redox architecture with local complexity; and 3) a glaciotectonic-thrusted redox architecture with high complexity. The baseflow N load at the catchment outlets reflect the contributions of N via oxic pathways through the complex redox architectures of the subsurface. We conclude that in some landscapes, the redox architecture cannot be simplified as a single interface that roughly follows the terrain; hence, thorough investigations of the structural heterogeneity of the local redox architectures will be necessary to improve simulations of N evolution along pathways and quantifications of N attenuation under various mitigation scenarios.

A DFT study on second-order NLO properties of bis-cyclometalated Iridium(III) complexes with chelating dicarbene auxiliary ligands

Iridium cyclometalated complexes with excellent nonlinear optical (NLO) properties in photophysical and redox properties have attracted considerable attention. The aim of this paper is calculate and analyze the redox effect on geometrical structures, UV–vis absorption spectra and second-order nonlinear optical (NLO) properties. The results show that the bis-cyclometalated Iridium(III) complexes have larger static first hyperpolarizabilities (βtot) values and they can be easily modulated by redox process. The redox complexes have obviously red-shifted with respect to the corresponding electronic transitions in the spectrum of neutral complexes to make the maximum absorption wavelength increased. And the βtot values of one-electron-reduced complexes are larger compared to that of oxidation state complexes and eigenstate. It is anticipative that the theoretical investigation of these iridium complexes will be helpful for providing an ideal model for redox switching of second-order NLO responses.

Specificity of the Redox Complex between Cytochrome P450 24A1 and Adrenodoxin Relies on Carbon-25 Hydroxylation of Vitamin-D Substrate

Metabolic deactivation of 1,25(OH)2D3 is initiated by modification of the vitamin-D side chain, as carried out by the mitochondrial cytochrome P450 24A1 (CYP24A1). In addition to its role in vitamin-D metabolism, CYP24A1 is involved in catabolism of vitamin-D analogs, thereby reducing their efficacy. CYP24A1 function relies on electron transfer from the soluble ferredoxin protein adrenodoxin (Adx). Recent structural evidence suggests that regioselectivity of the CYP24A1 reaction may correlate with distinct modes of Adx recognition. Here we used nuclear magnetic resonance (NMR) spectroscopy to monitor the structure of 15N-labeled full-length Adx from rat while forming the complex with rat CYP24A1 in the ligand-free state or bound to either 1,25(OH)2D3 or the vitamin-D supplement 1α(OH)D3. Although both vitamin-D ligands were found to induce a reduction in overall NMR peak broadening, thereby suggesting ligand-induced disruption of the complex, a crosslinking analysis suggested that ligand does not have a significant effect on the relative association affinities of the redox complexes. However, a key finding is that, whereas the presence of primary CYP24A1 substrate was found to induce NMR peak broadening focused on the putative recognition site α-helix 3 of rat adrenodoxin, the interaction in the presence of 1α(OH)D3, which is lacking the carbon-25 hydroxyl, results in disruption of the NMR peak broadening pattern, thus indicating a ligand-induced nonspecific protein interaction. These findings provide a structural basis for the poor substrate turnover of side-chain-modified vitamin-D analogs, while also confirming that specificity of the CYP24A1-ligand interaction influences specificity of CYP24A1-Adx recognition. SIGNIFICANCE STATEMENT: Mitochondrial cytochrome P450 enzymes, such as CYP24A1 responsible for catabolizing vitamin-D and its analogs, rely on a protein-protein interaction with a ferredoxin in order to receive delivery of the electrons required for catalysis. In this study, we demonstrate that this protein interaction is influenced by the enzyme-ligand interaction that precedes it. Specifically, vitamin-D missing carbon-25 hydroxylation binds the enzyme active site with high affinity but results in a loss of P450-ferredoxin binding specificity.

Fourier Transform Infrared Spectrovoltammetry and Quantitative Modeling of Analytes in Kinetically Constrained Redox Mixtures.

Redox-active analytes that do not support direct electron transfer on the electrode, such as proteins with buried redox centers, pose challenges to characterization of their structural and thermodynamic properties. Investigations of indirect transitions in analytes supported by complex redox mixtures require a careful balance between kinetic limitations and spectral interference from the mediators. Using methylene green and thionine acetate as redox mediators and myoglobin as the analyte, we demonstrate that normal pulse spectrovoltammetry (NPSV) with Fourier transform infrared (FT-IR) detection and subsequent global spectral regression analysis can resolve structural and thermodynamic properties simultaneously with little a priori information. Both the E1/2 and unbiased redox difference FT-IR spectra of the Fe(II)/Fe(III) redox couple of myoglobin in reduction and oxidation NPSV modes were in good agreement with those reported earlier by independent techniques. The thermodynamic and kinetic limitations of mediators/analyte interactions were investigated using comprehensive semiempirical kinetic simulation models. This modeling effort yielded a flexible computational tool capable of quantitatively predicting the redox response in mediated electrochemical studies and defining its limitations, thus greatly expanding the range and precision of the formal mediator/analyte concentration ratio rule.

Propuesta de sectores perspectivos para depósitos de hidrocarburos en la zona de Majaguillar-Martí, Cuba

El sector Majaguillar-Martí es de interés para incrementar las reservas probadas y probables Cuba, siendo el objetivo principal de este trabajo: proponer sectores perspectivos para depósitos de hidrocarburos en el mismo. Para esto se procesaron los campos potenciales, la aerogammaespectrometría y los datos del relieve, considerando los pozos y las manifestaciones de hidrocarburos presentes, todo sobre la base del modelo geológico correspondiente. Se estudiaron las zonas donde el relieve posee sutiles máximos residuales, los cuales podrían ser la causa de una mineralización carbonática y de sílice secundarias, vinculadas a microfiltraciones de hidrocarburos. Se obtuvo un mapa de anomalías complejas en el que se muestran las coincidencias espaciales correspondientes, fueron señaladas nueve áreas de interés, después de su comparación con la sísmica. Esta interpretación se validó, parcialmente, a partir de perfiles de reconocimiento del Complejo Redox realizado en dos de las áreas propuestas, cuyos resultados son mostrados en este trabajo.

Electrochemistry of Electroactive Species Loaded inside Polymeric Hydrogels. Effect of Viscoelastic Properties on Mass Transport and Heterogeneous Charge Transfer

The loading and mass transfer of electroactive species inside polymeric hydrogels is of interest in drug delivery, analytical chemistry and water remediation. The electrochemical properties of the species could be affected by the viscoelastic properties of the gel, local ionic force and pH, as well as interactions (e.g. hydrophobic) between the ions and the polymer chains. Usually, a thin film of the hydrogel is deposited on the electrode, loaded with electroactive species and electrochemically investigated. However, the mass transfer is controlled by finite diffusion and depends of an unknown, the thickness of the layer in the experimental conditions. On the other hand, we show here that a simple set-up, consisting of a disk electrode pressed on the soft hydrogel, allows performing electrochemistry of electroactve species (redox complexes, arsenite, nitrite) loaded inside the hydrogel matrix. The redox complexes are present as dilute solutions and the hydrogel dimensions fulfill the semi-infinite diffusion boundary conditions. Therefore, the data analysis can be performed using the theoretical framework developed for electrochemical measurements in liquid solutions. The physicochemical properties of the bulk hydrogels are evaluated by measuring the swelling kinetics, in the same conditions of the electrochemical measurements. Redox cations (e.g. tris(phenanthroline)iron(II) (TPFeII)) or anions (e.g. Fe(CN)6 -3, (FeCN) are loaded into anionic, neutral and cationic hydrogels showing no Donnan exclusion effects. The cyclic voltammetry of the loaded species show a quasireversible electron transfer mechanism (Eqre). The electrochemical parameters (diffusion coefficient and charge transfer constant) inside hydrogels are measured using chronoamperometry and digital simulation of the cyclic voltammetry. The Stokes-Einstein equation is used to calculate the effective viscosity of the hydrogel matrixes using the diffusion coefficients of redox complexes determined inside the hydrogels and in aqueous solutions (of known viscosities). The calculated viscosities correlate, with a negative slope, with the swelling rate constant of the hydrogel matrix. The heterogeneous charge transfer constants correlate with the calculated viscosities, revealing the effect of solvent dynamics on the charge transfer, according to Marcus theory for strongly adiabatic electron transfer. In that way, it is shown that the electrochemical measurements are able to monitor the local solvation properties of the hydrogel matrix. The method can be applied in electrochemical sensing of environmental contaminants. In the case of nitrite, the charge transfer is slow on glassy carbon (GC) electrodes. Therefore a redox catalyst (TPFeII) and nitrite are simultaneously absorbed in an anionic hydrogel and the redox electrocatalysis occurs inside the hydrogel matrix. On the other hand, the sensing of arsenite is made using Co oxide nanoparticles adsorbed on the GC electrode with arsenite loaded inside the hydrogel.