H2O2 Diffusion Research Articles

Effect of a novel low-concentration hydrogen peroxide bleaching gel containing nano-sized sodium trimetaphosphate and fluoride

ObjectivesTo evaluate in vitro the effects of nano-sized sodium trimetaphosphate (TMPnano) and sodium fluoride (F) added to a 17.5 % hydrogen peroxide (H2O2) bleaching gel on the color change, enamel mechanical and morphological properties, and H2O2 transamelodentinal diffusion. Materials and MethodsBovine enamel/dentin discs (n = 180) were divided according to the bleaching gel: 17.5 % H2O2 (17.5 % HP); 17.5 % H2O2 + 0.1 % F (HP/F); 17.5 % H2O2 + 1 % TMPnano (HP/TMPnano); 17.5 % H2O2 + 0.1 % F + 1 % TMPnano (HP/F/TMPnano) and 35 % H2O2 (35 % HP). The gels were applied for 40 min on three sessions, each session spaced 7 days apart. The total color change (ΔE*ab) according to the Commission Internationale de l'Eclairage (CIE) L*a*b* color change measured by CIEDE2000 (ΔE00), whitening index (ΔWID), surface hardness (SH), surface roughness (Ra), cross-sectional hardness (ΔKHN), and transamelodentinal diffusion were assessed. Enamel surfaces were examined using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDS) analysis. The data were analyzed using ANOVA, followed by the Student-Newman-Keuls test (p < 0.05). ResultsΔE*ab, ΔE00, and ΔWID values were comparable among the gels that produced a bleaching effect post-treatment (p < 0.001). The HP/F/TMPnano group exhibited lower mineral loss (SH and ΔKHN), Ra, and H2O2 diffusion compared to the 17.5 % HP and 35 % HP groups, which had the highest values (p < 0.001). SEM/EDS analysis revealed surface changes in all bleached groups, though these changes were less pronounced with F/TMPnano. ConclusionsThe 17.5 % HP gel containing F/TMPnano maintains the bleaching effect while reducing enamel demineralization, roughness, H2O2 diffusion, and enamel morphological changes. Clinical RelevanceLow-Concentration H2O2 bleaching gel containing F/TMPnano can be used as a novel approach to enhance safety and maintain the performance of aesthetic effects.

Self-dispersion of photocatalysts at oil-water interface accelerates H2O2 production and separation

Enhancing the efficiency of photocatalytic charge transfer for H2O2 production and in situ separation of H2O2 from aqueous suspension are crucial, especially when sacrificial agents are involved, for the advancement of this environmental-friendly process. In this study, we propose that the production and separation of H2O2 can be significantly enhanced at a self-assembled tri-phase system (water/photocatalyst/benzyl alcohol) compared to the suspension system. To prove this, we have employed titania nanotube (TNT) as a representative photocatalyst with efficient oxygen adsorption and modified it with organic ligand (octadecyl phosphate, OPA) and nickel species to modulate its hydrophobicity and dispersity at the interface, resulting in improved H2O2 yield. The modified TNT photocatalyst demonstrates efficient H2O2 production reaching a concentration of 5.1 mM after 75 mins under optimized conditions and an initial rate of 7500 μmol/g/h within first 6 h that even exceeding reported noble metals modified TiO2 photocatalysts. This enhanced activity is attributed to multiple effects including homogeneous dispersion of photocatalyst at the oil-water interface, efficient O2 adsorption and transfer, separated redox reactions at different phases, timely diffusion of H2O2 into bulk aqueous solution, and potential solvent-induced polarization effect on charge transfer, which result from the special oil-water interface that stabilizing photocatalysts and inducing photocatalytic O2 reduction. As proof-of-concept demonstrations show successful photosynthesis of H2O2 using natural solar light followed by utilizing the generated pure H2O2 solution for bacteria inactivation, indicating that interfacial photocatalytic systems offer promising potential for green H2O2 synthesis and application.

Solar H2O2 production with carbon dots and nickel co-modified titania nanotube photocatalyst stabilized at water/benzyl alcohol interface

An interfacial reaction system with the advantage of in situ H2O2 production and separation has been developed, in which titania nanotube (TNT) photocatalyst modified by nickel species and carbon dots (CDs) can self-stabilize at interface of water/benzyl alcohol. Under visible light irradiation, the CDs/Ni-TNT yields H2O2 with an initial rate of 385.6 μmol/g/h. The improved activity could be attributed to multiple effects such as sufficient oxygen adsorption and mass transfer, separated reduction and oxidation sites at different phases, and rapid diffusion of H2O2 from the interfacial region into bulk aqueous solution.

In-situ monitoring of cellular H2O2 within 3D cell clusters using conductive scaffolds

Accurately monitoring H2O2 concentrations in 3D cell clusters is challenging due to limited diffusion and rapid degradation of H2O2 in the culture medium. Despite the incorporation of three-dimensional cell culture approaches, the detection technology has largely remained as a 2D planar system. In this study, we present a versatile approach of 3D electrochemical sensing utilizing carbon nanotubes as conductive scaffolds for in-situ monitoring of H2O2 in cell clusters. These scaffolds enabled direct contact between H2O2 released from cells and the electrodes, thereby improving sensitivity and ensuring biocompatibility for cell aggregates. The scaffolds exhibited electrocatalytic behavior with a limit of detection of 6.7 nM H2O2. Additionally, the electrochemical responses of cell clusters with the scaffolds exhibited significantly higher current compared to clusters without scaffolds when stimulated with model drugs. This study underscores the potential of conductive scaffolds for real-time monitoring of H2O2 released from cell clusters in 3D microenvironments.

Effectiveness and safety of biosilicate-enhanced bleaching gels on enamel with early erosion lesion.

This study evaluated the efficacy and cytotoxicity of 35% hydrogen peroxide (HP) gel incorporated with 10% (w/w) biosilicate (BioS) on sound enamel and early-stage enamel erosion lesions. Discs of enamel/dentin were selected, subjected to erosive cycles (0.3% citric acid, pH 2.6), and treated with (n = 8): HP (35% HP, positive control); HP_BioS [carboxymethyl cellulose (CMC) + HP + BioS]; BioS (CMC + BioS); CMC (negative control). The discs were adapted to artificial pulp chambers with the enamel exposed for bleaching, and the dentin facing toward the culture medium (Dulbecco's modified Eagle's medium [DMEM]). Bleaching was performed in three 30-min sessions at 7-day intervals. After bleaching, the diffusion product (DMEM extract + diffused HP) was pipetted onto MDPC-23 odontoblastic cell line and inoculated. Color parameters (ΔL, Δa, Δb), color change (ΔE00), and changes in whiteness index (ΔWID) were determined before (T0) and after the last bleaching session (T3). Cell viability (MTT, %), H2O2 diffusion (μg/mL), oxidative cell stress (OxS), and cell fluorescence (live/dead assay, in confocal microscopy) were assessed (ANOVA/Tukey; α = 0.05). No difference in ΔL, Δa, Δb, ΔE00, and ΔWID were found between HP and HP_BioS (p > 0.05). The incorporation of BioS decreased the HP diffusion into the substrates and mitigated oxidative stress in early-stage eroded enamel (p < 0.05). HP_BioS presented significantly higher cell viability compared with HP under erosion conditions. Live/dead assay indicated that BioS_HP maintained viability with larger clusters of viable cells. Incorporating BioS into HP maintained bleaching effectiveness, favored cell viability, reduced the oxidative stress, and the cytotoxicity in teeth with early-stage erosion. BioS formulation showed promising results for reducing cytotoxicity in patients seeking tooth bleaching and presenting undetectable early-stage erosion.

Influence of coating dental enamel with a TiF4-loaded polymeric primer on the adverse effects caused by a bleaching gel with 35% H2O2

ObjectiveTo evaluate whether coating enamel with a polymeric primer (PPol) containing titanium tetrafluoride (TiF4) before applying a bleaching gel with 35% H2O2 (35% BG) increases esthetic efficacy, prevents changes in morphology and hardness of enamel, as well as reduces the cytotoxicity from conventional in-office bleaching. Materials and methodsStandardized enamel/dentin discs were stained and bleached for 45 min (one session) with 35% BG. Groups 2TiF4, 6TiF4, and 10TiF4 received the gel on the enamel previously coated with PPol containing 2 mg/mL, 6 mg/mL, or 10 mg/mL, respectively. No treatment or application of 35% BG directly on enamel were used as negative control (NC), and positive control (PC), respectively. UV-reflectance spectrophotometry (CIE L*a*b* system, ΔE00, and ΔWI, n = 8) determined the bleaching efficacy of treatments. Enamel microhardness (Knoop, n = 8), morphology, and composition (SEM/EDS, n = 4) were also evaluated. Enamel/dentin discs adapted to artificial pulp chambers (n = 8) were used for trans-amelodentinal cytotoxicity tests. Following the treatments, the extracts (culture medium + bleaching gel components diffused through the discs) were collected and applied to odontoblast-like MDPC-23 cells, which were assessed concerning their viability (alamarBlue, n = 8; Live/Dead, n = 4), oxidative stress (n = 8), and morphology (SEM). The amount of H2O2 in the extracts was also determined (leuco crystal violet/peroxidase, n = 8). The numerical data underwent one-criterion variance analysis (one-way ANOVA), followed by Tukey's test, at a 5% significance level. ResultsRegarding the ΔE00, no difference was observed among groups 2TiF4, 6TiF4, and PC (p > 0.05). The ΔWI was similar between groups 2TiF4 and PC (p > 0.05). The ΔWI of group 6TiF4 was superior to PC (p < 0.05), and group 10TiF4 achieved the highest ΔE00 and ΔWI values (p < 0.05). Besides limiting enamel microstructural changes compared to PC, group 10TiF4 significantly increased the hardness of this mineralized dental tissue. The highest cellular viability occurred in 10TiF4 compared to the other bleached groups (p < 0.05). Trans-amelodentinal H2O2 diffusion decreased in groups 2TiF4, 6TiF4, and 10TiF4 in comparison with PC (p < 0.05). ConclusionCoating enamel with a PPol containing TiF4 before applying a 35% BG may increase enamel microhardness and esthetic efficacy and reduce the trans-amelodentinal cytotoxicity of conventional in-office tooth bleaching. The PPol containing 10 mg/mL of TiF4 promoted the best outcomes.

Using the heme peroxidase APEX2 to probe intracellular H2O2 flux and diffusion

Currently available genetically encoded H2O2 probes report on the thiol redox state of the probe, which means that they reflect the balance between probe thiol oxidation and reduction. Here we introduce the use of the engineered heme peroxidase APEX2 as a thiol-independent chemogenetic H2O2 probe that directly and irreversibly converts H2O2 molecules into either fluorescent or luminescent signals. We demonstrate sensitivity, specificity, and the ability to quantitate endogenous H2O2 turnover. We show how the probe can be used to detect changes in endogenous H2O2 generation and to assess the roles and relative contributions of endogenous H2O2 scavengers. Furthermore, APEX2 can be used to study H2O2 diffusion inside the cytosol. Finally, APEX2 reveals the impact of commonly used alkylating agents and cell lysis protocols on cellular H2O2 generation.

Blockage of aquaporin-3 peroxiporin activity by organogold compounds affects melanoma cell adhesion, proliferation and migration.

Aquaporin-3 (AQP3) is a membrane channel with dual aquaglyceroporin/peroxiporin activity, facilitating the diffusion of water, glycerol and H2O2 across cell membranes. AQP3shows aberrant expression in melanoma and its role in cell adhesion, migration and proliferation is well described. Gold compounds were shown to modulate AQP3 activity with reduced associated toxicity, making them promising molecules for cancer therapy. In this study, we validated the phenotype resulting from AQP3-silencing of two melanoma cell lines, MNT-1 and A375, which resulted in decreased H2O2 permeability. Subsequently, the AQP3 inhibitory effect of a new series of organogold compounds derived from Auphen, a potent AQP3 inhibitor, was first evaluated in red blood cells (RBCs) that highly express AQP3, and then in HEK-293T cells with AQP3 overexpression to ascertain the compounds' specificity. The first screening in RBCs unveiled two organogold compounds as promising blockers of AQP3 permeability. Moderate reduction of glycerol permeability but drastic inhibition of H2O2 permeability was detected for some of the gold derivatives in both AQP3-overexpressing cells and human melanoma cell lines. Additionally, all compounds were effective in impairing cell adhesion, proliferation and migration, although in a cell type-dependent manner. In conclusion, our data show that AQP3 peroxiporin activity is crucial for melanoma progression and highlight organogold compounds as promising AQP3 inhibitors with implications in melanoma cell adhesion, proliferation and migration, unveiling their potential as anticancer drugs against AQP3-overexpressing tumours. KEY POINTS: AQP3 affects cellular redox balance. Gold compounds inhibit AQP3 permeability in melanoma cells. AQP3 is involved in cell adhesion, proliferation and migration of melanoma. Blockage of AQP3 peroxiporin activity impairs melanoma cell migration. Gold compounds are potential anticancer drug leads for AQP3-overexpressing cancers.

Electroenzymatic cascade reaction on a biohybrid boosts the chiral epoxidation reaction

The chiral epoxidation of styrene and its derivatives is an important transformation that has attracted considerable scientific interest in the chemical industry. Herein, we integrate enzymatic catalysis and electrocatalysis to propose a new route for the chiral epoxidation of styrene and its derivatives. Chloroperoxidase (CPO) functionalized with 1-ethyl-3-methylimidazolium bromide (ILEMB) was loaded onto cobalt nitrogen-doped carbon nanotubes (CoN@CNT) to form a biohybrid (CPO-ILEMB/CoN@CNT). H2O2 species were generated in situ through a two-electron oxygen reduction reaction (2e–ORR) at CoN@CNT to initiate the following enzymatic epoxidation of styrene by CPO. CoN@CNT had high electroactivity for the ORR to produce H2O2 at a more positive potential, prohibiting the conversion of FeIII to FeII in the heme of CPO to maintain enzymatic activity. Meanwhile, CoN@CNT could serve as an ideal carrier for the immobilization of CPO-ILEMB. Hence, the coimmobilization of CPO-ILEMB and CoN@CNT could facilitate the diffusion of intermediate H2O2, which achieved 17 times higher efficiency than the equivalent amounts of free CPO-ILEMB in bulk solution for styrene epoxidation. Notably, an enhancement (∼45%) of chiral selectivity for the epoxidation of styrene was achieved.

A new method to measure aquaporin-facilitated membrane diffusion of hydrogen peroxide and cations in plant suspension cells.

Plant aquaporins (AQPs) facilitate the membrane diffusion of water and small solutes, including hydrogen peroxide (H2 O2 ) and, possibly, cations, essential signalling molecules in many physiological processes. While the determination of the channel activity generally depends on heterologous expression of AQPs in Xenopus oocytes or yeast cells, we established a genetic tool to determine whether they facilitate the diffusion of H2 O2 through the plasma membrane in living plant cells. We designed genetic constructs to co-express the fluorescent H2 O2 sensor HyPer and AQPs, with expression controlled by a heat shock-inducible promoter in Nicotiana tabacum BY-2 suspension cells. After induction of ZmPIP2;5 AQP expression, a HyPer signal was recorded when the cells were incubated with H2 O2 , suggesting that ZmPIP2;5 facilitates H2 O2 transmembrane diffusion; in contrast, the ZmPIP2;5W85A mutated protein was inactive as a water or H2 O2 channel. ZmPIP2;1, ZmPIP2;4and AtPIP2;1 also facilitated H2 O2 diffusion. Incubation with abscisic acid and the elicitor flg22 peptide induced the intracellular H2 O2 accumulation in BY-2 cells expressing ZmPIP2;5. We also monitored cation channel activity of ZmPIP2;5 using a novel fluorescent photo-switchable Li+ sensor in BY-2 cells. BY-2 suspension cells engineered for inducible expression of AQPs as well as HyPer expression and the use of Li+ sensors constitute a powerful toolkit for evaluating the transport activity and the molecular determinants of PIPs in living plant cells.

Influence of bleaching gels formulated with nano-sized sodium trimetaphosphate and fluoride on the physicochemical, mechanical, and morphological properties of dental enamel

ObjectivesTo evaluate in vitro the effects of sodium fluoride (F) and nano-sized sodium trimetaphosphate (TMPnano) added to a 35% hydrogen peroxide (H2O2) bleaching gel on the color alteration, enamel mechanical and morphological properties, and H2O2 transamelodentinal diffusion. Materials and MethodsBovine enamel/dentin discs (n = 180) were divided according to the bleaching gel: 35% H2O2 (HP); 35% H2O2 + 0.1% F (HP/F); 35% H2O2 + 1% TMPnano (HP/TMPnano); 35% H2O2 + 0.1% F + 1% TMPnano (HP/F/TMPnano) and 35% H2O2 + 2% calcium gluconate (HP/Ca). The gels were applied 3 times by 40 min; once each 7-day. The Commission Internationale de l'Eclairage (CIE) L*a*b* total color alteration (ΔE), color alteration by CIEDE2000 (ΔE00), whitening index (ΔWID), surface (SH) and cross-sectional hardness (ΔKHN), surface roughness (Ra), and transamelodentinal diffusion were determined. Enamel surfaces were evaluated by Scanning Electron Microscopy (SEM) and X-ray Dispersive Energy (EDX). Data were submitted to ANOVA, followed by the Student-Newman-Keuls test (p <0.05). ResultsΔE, ΔE00, and ΔWID were similar among the gels that promoted a bleaching effect after treatment (p <0.001). Mineral loss (SH and ΔKHN), Ra, and H2O2 diffusion were lower for HP/F/TMPnano; the HP and HP/Ca groups presented the highest values (p <0.001). For SEM/EDX, surface changes were observed in all bleached groups, but less intense with TMPnano. ConclusionsGels containing F/TMPnano do not interfere with the bleaching effect and reduce enamel demineralization, roughness, H2O2 diffusion, and morphological changes. Clinical RelevanceWhitening gels containing F/TMPnano can be used as a new strategy to increase safety and maintain clinical performance.

Graphene oxide partially exfoliated from carbon cloth: A new Paradigm of photocathode for Solar–Driven photoelectrochemistry

A critical factor limiting the photoelectrocatalytic reaction rate over semiconductors is severe photogenerated charge–carrier recombination, which is well–circumvented in this study by using graphene oxide (GO) partially exfoliated from carbon cloth (CC) as the photoelectrode. A kinetic model is proposed for the first time to rationalize the outstanding photoelectrochemical activity of GO/CC by accounting for the photoexcited charge carrier generation induced by harvesting of broadband sunlight mostly by GO. The photogenerated electron–hole pairs are thereby close to the GO/CC–electrolyte liquid junction and are rectified by surface band bending to flow in opposite directions. The charge recombination is hence largely suppressed and further quenched considering the high–lying conduction band extremum of GO, which favors injection of the photoexcited electrons into the electrolyte. As an important result of efficient charge separation, the photogenerated charge carriers relax mostly via the reaction with H2O2 in the electrolyte, as evidenced by the steady–state photocurrent density of GO/CC depending linearly on the light intensity and by the transient time constant of the time–resolved photocurrent response of GO/CC to chopped solar irradiation being primarily dictated by the diffusion and dissociative adsorption rate of H2O2 on GO/CC.

All-optical spatiotemporal mapping of ROS dynamics across mitochondrial microdomains in situ

Hydrogen peroxide (H2O2) functions as a second messenger to signal metabolic distress through highly compartmentalized production in mitochondria. The dynamics of reactive oxygen species (ROS) generation and diffusion between mitochondrial compartments and into the cytosol govern oxidative stress responses and pathology, though these processes remain poorly understood. Here, we couple the H2O2 biosensor, HyPer7, with optogenetic stimulation of the ROS-generating protein KillerRed targeted into multiple mitochondrial microdomains. Single mitochondrial photogeneration of H2O2 demonstrates the spatiotemporal dynamics of ROS diffusion and transient hyperfusion of mitochondria due to ROS. This transient hyperfusion phenotype required mitochondrial fusion but not fission machinery. Measurement of microdomain-specific H2O2 diffusion kinetics reveals directionally selective diffusion through mitochondrial microdomains. All-optical generation and detection of physiologically-relevant concentrations of H2O2 between mitochondrial compartments provide a map of mitochondrial H2O2 diffusion dynamics in situ as a framework to understand the role of ROS in health and disease.

Pitfalls of Mitochondrial Redox Signaling Research.

Redox signaling from mitochondria (mt) to the cytosol and plasma membrane (PM) has been scarcely reported, such as in the case of hypoxic cell adaptation or (2-oxo-) 2-keto-isocaproate (KIC) β-like-oxidation stimulating insulin secretion in pancreatic β-cells. Mutual redox state influence between mitochondrial major compartments, the matrix and the intracristal space, and the cytosol is therefore derived theoretically in this article to predict possible conditions, when mt-to-cytosol and mt-to-PM signals may occur, as well as conditions in which the cytosolic redox signaling is not overwhelmed by the mitochondrial antioxidant capacity. Possible peroxiredoxin 3 participation in mt-to-cytosol redox signaling is discussed, as well as another specific case, whereby mitochondrial superoxide release is diminished, whereas the matrix MnSOD is activated. As a result, the enhanced conversion to H2O2 allows H2O2 diffusion into the cytosol, where it could be a predominant component of the H2O2 release. In both of these ways, mt-to-cytosol and mt-to-PM signals may be realized. Finally, the use of redox-sensitive probes is discussed, which disturb redox equilibria, and hence add a surplus redox-buffering to the compartment, where they are localized. Specifically, when attempts to quantify net H2O2 fluxes are to be made, this should be taken into account.

A Theory of Mechanical Stress-Induced H2O2 Signaling Waveforms in Planta

Recent progress in nanotechnology-enabled sensors that can be placed inside of living plants has shown that it is possible to relay and record real-time chemical signaling stimulated by various abiotic and biotic stresses. The mathematical form of the resulting local reactive oxygen species (ROS) wave released upon mechanical perturbation of plant leaves appears to be conserved across a large number of species, and produces a distinct waveform from other stresses including light, heat and pathogen-associated molecular pattern (PAMP)-induced stresses. Herein, we develop a quantitative theory of the local ROS signaling waveform resulting from mechanical stress in planta. We show that nonlinear, autocatalytic production and Fickian diffusion of H2O2 followed by first order decay well describes the spatial and temporal properties of the waveform. The reaction-diffusion system is analyzed in terms of a new approximate solution that we introduce for such problems based on a single term logistic function ansatz. The theory is able to describe experimental ROS waveforms and degradation dynamics such that species-dependent dimensionless wave velocities are revealed, corresponding to subtle changes in higher moments of the waveform through an apparently conserved signaling mechanism overall. This theory has utility in potentially decoding other stress signaling waveforms for light, heat and PAMP-induced stresses that are similarly under investigation. The approximate solution may also find use in applied agricultural sensing, facilitating the connection between measured waveform and plant physiology.

Gold Nanoclusters with Two Sets of Embedded Enzyme Nanoparticles for Applications as Electrochemical Sensors for Glucose

Enzyme-based electrochemical biosensors have been widely used because of their sensitivity, rapidity, and highly target-specific reactions. However, the immobilized enzymes can hinder electron transfer on the surface of the electrode and can decrease the sensitivity of electrochemical biosensors. To overcome this problem, we synthesized conductive gold nanoclusters with two sets of embedded enzyme nanoparticles, which are called gold nanocluster-embedded dual-enzyme nanoparticles (AuNC-DENPs) composed of a glucose oxidase-stabilized gold nanocluster (GOX-AuNC) and a horseradish peroxide-stabilized gold nanocluster (HRP-AuNC). Moreover, the application of these nanoparticles as an enzyme-based highly sensitive electrochemical sensor was investigated. Owing to the effect of AuNCs, these nanoparticles have good conductivity compared to bare protein nanoparticles. In addition, the synthesized AuNC-DENPs enabled the combination of a two-enzyme cascade reaction, in which the GOX-AuNC component of the nanoparticle oxidized glucose to generate hydrogen peroxide, which then reacted with the adjacent HRP-AuNC component on the nanoparticle. Given the proximity of the two enzyme components in a single nanoparticle, the AuNC-DENPs markedly reduced the diffusion and decomposition of H2O2 during the cascade reaction and showed an enhanced catalytic reaction compared to a mixture of enzymes. As a result, the biosensor exhibited high sensitivity (18,944 μA/mM cm2) and could detect very low concentrations of glucose ranging from 5 to 320 nM and a LOD of 2.58 nM. In addition, by analyzing nontarget materials and serum together with glucose, it was confirmed that the sensor has good selectivity for glucose.

A reusable electrochemiluminescence biosensor controlled by a nanochannel gating system for T-2 toxin detection

A reusable electrochemiluminescence (ECL) biosensor based on the switchable gating property of nanochannels has been successfully developed and applied in the detection of T-2 toxin. The sensing interface was achieved by modifying nanoporous anodic aluminum oxide membrane with gold nanoparticles and T-2 aptamers, which has a switchable gating property triggered by the target. Once triggered by the target, the gating system could be switched from the "OFF" state to the "ON" state allowing diffusion of ascorbic acid (AA) and H2O2. Due to the consumption of reactive oxygen species by AA, ECL signals of luminol/Au NPs was significantly inhibited. Through the treatment of heating and washing, captured T-2 toxin can be fully released and the gating system can be switched to the “OFF” state and applied in the following detection. Due to the spatial separation, reactivation of the sensing interface by repeated heating and washing will not affect the ECL emitters after repeated tests. This biosensor was applied in the analysis of actual samples. There’s a good linear relationship between ECL intensity and the logarithm value of the concentration in the range of 10 pg mL−1 to 100 μg mL−1 with a limit of detection of 3.2 pg mL−1.

Development of a Redox-Polymer-Based Electrochemical Glucose Biosensor Suitable for Integration in Microfluidic 3D Cell Culture Systems.

The inclusion of online, in situ biosensors in microfluidic cell cultures is important to monitor and characterize a physiologically mimicking environment. This work presents the performance of second-generation electrochemical enzymatic biosensors to detect glucose in cell culture media. Glutaraldehyde and ethylene glycol diglycidyl ether (EGDGE) were tested as cross-linkers to immobilize glucose oxidase and an osmium-modified redox polymer on the surface of carbon electrodes. Tests employing screen printed electrodes showed adequate performance in a Roswell Park Memorial Institute (RPMI-1640) media spiked with fetal bovine serum (FBS). Comparable first-generation sensors were shown to be heavily affected by complex biological media. This difference is explained in terms of the respective charge transfer mechanisms. Under the tested conditions, electron hopping between Os redox centers was less vulnerable than H2O2 diffusion to biofouling by the substances present in the cell culture matrix. By employing pencil leads as electrodes, the incorporation of these electrodes in a polydimethylsiloxane (PDMS) microfluidic channel was achieved simply and at a low cost. Under flow conditions, electrodes fabricated using EGDGE presented the best performance with a limit of detection of 0.5 mM, a linear range up to 10 mM, and a sensitivity of 4.69 μA mM-1 cm-2.

Dynamic coordination of two-phase reactions in heterogeneous Fenton for selective removal of water pollutants

The •OH-mediated heterogeneous Fenton reaction has been widely applied despite the limitations of low pollutant selectivity and unclear oxidation mechanism. Here we reported an adsorption-assisted heterogeneous Fenton process for the selective degradation of pollutants and systematically illustrated its dynamic coordination in two phases. The results showed that the selective removal was improved by (i) surface enrichment of target pollutants via electrostatic interactions including real adsorption and adsorption-assisted degradation and (ii) inducing the diffusion of H2O2 and pollutants from the bulk solution to the catalyst surface to trigger the homogeneous and surface heterogeneous Fenton reactions. Furthermore, surface adsorption was confirmed as a crucial but not necessary step for degradation. Mechanism studies demonstrated that •O2– and Fe3+/Fe2+ cycle increased •OH generation, which remained active in two phases within ⁓244 nm. These findings are critical for understanding the removal behavior of complex targets and expanding heterogeneous Fenton applications.

Construction of novel bienzyme-inorganic hybrid nanoflowers beads and their application in the efficient degradation of acridine

To develop a biocatalyst with high efficiency, stability and reusability for the degradation of organic pollutant acridine in wastewater, a novel biocatalyst named bienzyme-inorganic hybrid nanoflowers beads were successfully prepared in the present work, designated as biE-HNFs-beads. This bienzyme biocatalyst composed of bienzyme-inorganic hybrid nanoflowers and traditional beads carriers were characterized by SEM, TEM, FT-IR, XRD, and EPR. The biE-HNFs-beads showed better stability, recyclability and improved catalytic activity for acridine degradation than that of free bienzyme. Furthermore, biE-HNFs-beads could reduce the diffusion and decomposition of the intermediate H2O2 through the bienzyme cascade reactions, which not only improved the stability of the bienzyme, but also accelerated the degradation of acridine. Under optimized conditions, the degradation rate of acridine by biE-HNFs-beads could reach 99.9 %. The stability study indicated that the biE-HNFs-beads exhibited enhanced stability, reusability and storage stability. Besides, the bioconversion products analysis of acridine degraded by biE-HNFs-beads biocatalyst were identified by LC-MS, and the enzymatic degradation pathway of acridine was inferred for the first time.