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Simple Summary: Cancer cells grow and divide so rapidly that they are literally engaged in a metabolic marathon—leading to the formation of high levels of reactive oxygen species (ROS). The altered redox balance in cancer cells offers therapeutic opportunities for targeting cancer. Some ROS-targeting strategies attempt to enhance ROS production to inflict lethal cell damage or trigger apoptosis, while other anticancer agents inhibit enzymes that are essential to maintain the redox potential of the cell. One type of ROS that shows potential to be utilized as a treatment mechanism is hydrogen peroxide (H2O2), which can be generated by numerous mechanisms, including metal-based prodrugs, photodynamic therapy, enzymes, nanoparticles, chemical modulators, and various combinations thereof. This review focuses on various chemical agents that induce H2O2-mediated cancer cell death, including their mechanism of function, preclinical and clinical studies, recent advancements, and potential applications as a new and exciting avenue for targeted and efficacious cancer treatment. Cancer cells show altered antioxidant defense systems, dysregulated redox signaling, and increased generation of reactive oxygen species (ROS). Targeting cancer cells through ROS-mediated mechanisms has emerged as a significant therapeutic strategy due to its implications in cancer progression, survival, and resistance. Extensive research has focused on selective generation of H2O2 in cancer cells for selective cancer cell killing by employing various strategies such as metal-based prodrugs, photodynamic therapy, enzyme-based systems, nano-particle mediated approaches, chemical modulators, and combination therapies. Many of these H2O2-amplifying approaches have demonstrated promising anticancer effects and selectivity in preclinical investigations. They selectively induce cytotoxicity in cancer cells while sparing normal cells, sensitize resistant cells, and modulate the tumor microenvironment. However, challenges remain in achieving selectivity, addressing tumor heterogeneity, ensuring efficient delivery, and managing safety and toxicity. To address those issues, H2O2-generating agents have been combined with other treatments leading to optimized combination therapies. This review focuses on various chemical agents/approaches that kill cancer cells via H2O2-mediated mechanisms. Different categories of compounds that selectively generate H2O2 in cancer cells are summarized, their underlying mechanisms and function are elucidated, preclinical and clinical studies as well as recent advancements are discussed, and their prospects as targeted therapeutic agents and their therapeutic utility in combination with other treatments are explored. By understanding the potential of these compounds, researchers can pave the way for the development of effective and personalized cancer treatments. [ABSTRACT FROM AUTHOR]

Herein, a carbon felt (CF) cathode modified by the acidic oxidised carbon nanotubes (OCNTs) exhibited a high yield of the H2O2 generation in electro-Fenton. Rotating disk electrode (RDE) measurements showed that the selective generation of H2O2 occurred on the CF cathode coated by OCNTs (OCNTs/CF), which was attributed to the high amount of oxygen-containing functional groups in OCNTs. Moreover, the pollutant degradation efficiency could almost reach 100% within 60 min in electro-Fenton with OCNTs/CF as the cathode. Furthermore, the pollutant removal efficiency was kept constant after five consecutive cycles, indicating the high stability of OCNTs/CF cathode. Besides, the hydrophilicity of OCNTs/CF cathode was significantly enhanced owing to the abundant oxygen-contained functional groups on the surface of the OCNTs/CF cathode, which facilitated the mass transfer between the OCNTs/CF cathode and the reactants in the bulk solution. To reveal the possible mechanism in electro-Fenton equipped with the OCNTs/CF cathode, quenching experiments and electron paramagnetic resonance (EPR) investigations were further conducted. This work provided valuable insights into the fabrication of the non-metallic cathode with a high ability towards H2O2 generation in electro-Fenton for efficient pollutant removal. [ABSTRACT FROM AUTHOR]

Metal‐Organic Frameworks (MOFs) hold great potential to be used as porous (photo)‐electrocatalytic platforms containing large concentration of immobilized molecular catalysts. Indeed, the use of MOFs in a photo‐electrochemical devices was recently demonstrated. However, so far there are no reports of MOFs used for photo‐electrochemical O2 reduction to H2O2. Herein, we utilize a Co‐porphyrin based MOF (Co‐MOF‐525), that produces H2O2 at high faradaic efficiency (95 %), both electrochemically and photo‐electrochemically. Electrochemical characterization show that the active catalytic site is a MOF‐tethered Co(I)‐porphyrin. Additionally, under light illumination, the MOF's intrinsic catalytic rate is significantly accelerated compared to dark electrolysis conditions. Thus, this work could open a path for future implementation of photoactive MOFs in solar fuel schemes. [ABSTRACT FROM AUTHOR]

Abstract Metal‐Organic Frameworks (MOFs) hold great potential to be used as porous (photo)‐electrocatalytic platforms containing large concentration of immobilized molecular catalysts. Indeed, the use of MOFs in a photo‐electrochemical devices was recently demonstrated. However, so far there are no reports of MOFs used for photo‐electrochemical O2 reduction to H2O2. Herein, we utilize a Co‐porphyrin based MOF (Co‐MOF‐525), that produces H2O2 at high faradaic efficiency (95 %), both electrochemically and photo‐electrochemically. Electrochemical characterization show that the active catalytic site is a MOF‐tethered Co(I)‐porphyrin. Additionally, under light illumination, the MOF's intrinsic catalytic rate is significantly accelerated compared to dark electrolysis conditions. Thus, this work could open a path for future implementation of photoactive MOFs in solar fuel schemes.

Visible‐light‐driven semiconductor photoelectrodes are promising new devices for on‐demand photocathodic generation of hydrogen peroxide. Herein, the fabrication of organic polymeric photocathodes employing poly(4,7‐di(thiophen‐2‐yl)benzo[c][1,2,5]thiadiazole) (pThBTD), and comparatively seven other related derivatives is reported. The monomer dithienobenzodithiazole can be directly polymerized on an electrode via two methods: electropolymerization or iodine‐vapor‐assisted polymerization. Both give polymers with wide visible light absorption and suitable stability for photoelectrodes. These methods yield different active layer morphologies, with electropolymerization yielding photocathodes with better performance. Critical issues affecting oxygen reduction photocurrents are evaluated, namely thickness, wettability, and pH. Photocathodic oxygen reduction currents, as well as photovoltages, are among the highest reported for an organic photoelectrocatalyst, and pThBTD films can stably produce H2O2 with high faradaic yield over at least 8 h. This study shows that single‐component organic semiconductor devices can be highly competitive versus more complex heterostructures and that such low‐bandgap organic polymers can afford remarkable stability. [ABSTRACT FROM AUTHOR]

Combining a rational design strategy with a simple synthetic method to produce an eco-friendly material presents a unique challenge in photocatalysis technology. This work reports the successful synthesis of a heteroanionic titanium oxycarbide photocatalyst—TiO0.25C0.75 (TiOC) via a solid-state reaction and employed for the decomposition of Congo red (CR) and H2O2 generation from water under visible light radiation. Initially, TiOC demonstrated a moderate CR degradation efficiency of 54% (1 g/L) in 120 min and evolved a minimal amount of H2O2 after 90 min (2 mmol) and 120 min (10 mmol) of light exposure. This clearly indicates that the localization of hybridization of O-2p and C-2p orbitals and a more positive conduction band edge (CB) of TiOC lead to reduced carrier mobility and, consequently, high recombination of photogenerated charge carriers. Therefore, sacrificial reagents such as H2O2 and isopropyl alcohol (ISA) were employed to improve CR removal and H2O2 evolution rate, resulting in 70% and 21.5 mmol (120 min), respectively. [ABSTRACT FROM AUTHOR]

Four highly porous covalent organic frameworks (COFs) containing pyrene units were prepared and explored for photocatalytic H2O2 production. The experimental studies are complemented by density functional theory calculations, proving that the pyrene unit is more active for H2O2 production than the bipyridine and (diarylamino)benzene units reported previously. H2O2 decomposition experiments verified that the distribution of pyrene units over a large surface area of COFs plays an important role in catalytic performance. The Py‐Py‐COF though contains more pyrene units than other COFs which induces a high H2O2 decomposition due to a dense concentration of pyrene in close proximity over a limited surface area. Therefore, a two‐phase reaction system (water‐benzyl alcohol) was employed to inhibit H2O2 decomposition. This is the first report on applying pyrene‐based COFs in a two‐phase system for photocatalytic H2O2 generation. [ABSTRACT FROM AUTHOR]

Abstract Visible‐light‐driven semiconductor photoelectrodes are promising new devices for on‐demand photocathodic generation of hydrogen peroxide. Herein, the fabrication of organic polymeric photocathodes employing poly(4,7‐di(thiophen‐2‐yl)benzo[c][1,2,5]thiadiazole) (pThBTD), and comparatively seven other related derivatives is reported. The monomer dithienobenzodithiazole can be directly polymerized on an electrode via two methods: electropolymerization or iodine‐vapor‐assisted polymerization. Both give polymers with wide visible light absorption and suitable stability for photoelectrodes. These methods yield different active layer morphologies, with electropolymerization yielding photocathodes with better performance. Critical issues affecting oxygen reduction photocurrents are evaluated, namely thickness, wettability, and pH. Photocathodic oxygen reduction currents, as well as photovoltages, are among the highest reported for an organic photoelectrocatalyst, and pThBTD films can stably produce H2O2 with high faradaic yield over at least 8 h. This study shows that single‐component organic semiconductor devices can be highly competitive versus more complex heterostructures and that such low‐bandgap organic polymers can afford remarkable stability.

Carbon-based electrodes have been extensively used as cathodes for the electro-generation of H₂O₂, which is used in the production of the hydroxyl radical •OH to mineralize organic compounds in several types of wastewater. Carbon cloth has been also used in combination with activated carbon for the combined adsorption and oxidation of persistent organic compounds present in tequila vinasse wastewater. Whereas most of the works regarding the H₂O₂ electro-generation involve relatively complex processes to enhance the catalytic activity or the electrochemically active area of these electrodes, calcination by itself represents a simple and low-cost option to enhance these cathodic and anodic functions, especially in the fabrication of large area electrodes that could be needed to treat the large amount of tequila vinasse wastewater that is produced daily. In this work, the effect of calcination at 300°C and 600°C of carbon clothes in the oxidation current and H₂O₂ production at different potentials in H₂SO₄ was studied. Oxidation current increased 700% upon calcination at 600°C, compared to no calcination. H₂O₂ was produced only in a narrow range of polarizations, whereas calcination at 600 °C increased the generation rate from 7.1 ± 0.3 to 17.8 ± 0.4 mg L⁻1 h⁻1.

Intratumoral injections can reduce systemic absorption and deliver large amounts of drugs to the tumor, thereby reducing side effects and exhibiting high therapeutic efficacy. Therefore, a variety of drug delivery systems, such as hydrogels, fine particles, and nanoparticles, have been studied. Although the sustained-release drug delivery system can effectively reduce systemic absorption due to the slow release of the drug from the site of intratumoral injection, it lacks the ability to deliver high concentrations of drugs to the tumor. In particular, the larger the tumor size, the lower the efficacy of the treatment. To address this problem, this study focused on the tumor structure. Owing to the three-dimensional structure of the dense tumor microenvironment (TME) and abnormal blood vessels, drugs administered directly into the tumor act as if they were encapsulated in a hydrogel. To evaluate whether the three-dimensional structure of the tumor affects the intratumoral distribution and systemic absorption of drugs, needle-type starch implants (GOD-NS implants) and needle-type gelatin implants (GOD-NG implants) containing glucose oxidase (GOD), a protein that exhibits anti-cancer effects through hydrogen peroxide (H2O2) generation, were prepared. Both GOD-NS and GOD-NG implants can be easily injected into tumors. GOD-NS implants released GOD slowly, whereas GOD-NG implants released most of the GOD within 1 h. When a GOD-NG implant that rapidly released GOD was also injected, a high concentration of GOD was maintained in the tumor for a long time as it was trapped in the three-dimensional structure of the tumor. This study demonstrated that intratumoral injection of a rapidly drug-releasing gelatin needle may be a novel drug delivery system capable of long-term retention of high drug concentrations in tumors, as the three-dimensional structure of the tumor affects drug delivery.

For optimizing H 2 O 2 generation in three-dimensional electro-Fenton (3D-EF) to enhance efficacy in treating organic wastewater, a comprehensive analysis from various perspectives of H 2 O 2 generation was provided. By quantifying the generation of H 2 O 2 within the reaction system and comparing it with the changing trends in organic wastewater treatment efficiency, a close correlation between H 2 O 2 generation and organic wastewater treatment was revealed. A reliable and accurate kinetic model for H 2 O 2 generation was formulated by building upon the reactions of H 2 O 2 with electrodes and coexisting substances. The mathematical formulation of the kinetic model pinpointed pivotal factors influencing H 2 O 2 generation, including current density, dissolved oxygen concentration, and the Fe catalytic activity substance. The experimental data and fitted results under various conditions indicated that the model could reasonably and accurately describe the relationship between pivotal factors and the quantity of generated H 2 O 2. Crucial strategies were proposed to enhance H 2 O 2 generation in the 3D-EF system by drawing from the impact rules of pivotal factors on H 2 O 2 generation. These strategies primarily focused on improving electrode performance, optimizing reactor conditions, and refining particle electrode preparation processes. [Display omitted] • Correlation between H 2 O 2 generation and organic wastewater treatment was revealed. • A kinetic model was formulated to describe H 2 O 2 generation accurately. • Multianalysis was conducted on the impact of pivotal factors on H 2 O 2 generation. • Process enhancement strategies were proposed to optimize H 2 O 2 generation. [ABSTRACT FROM AUTHOR]

Ferroptosis is a newly form of regulated cell death, which has attracted great attention for tumor therapy. Herein, we prepared nanoscale coordination polymer Fe-NQA particles to deliver iron and NQA (vitamin K3 derivative) into tumor cells, which synergistically promoted ferroptotic therapy for inhibiting tumor growth, preventing metastasis, and overcoming radioresistance. [ABSTRACT FROM AUTHOR]

The investigation of an artificial photosynthesis system for contaminant treatment and consecutive hydrogen peroxide formation is imperative but challenging, whereas the conversion efficiency is relatively low and far away from the demand for social development. Herein, oxygen and sulphur were collectively introduced into carbon nitride nanosheets (OSCN), together with sufficient edge and basal plane active sites. The as-synthesized sample could achieve a degradation efficiency of 84% for 100 mg/L tetracycline hydrochloride, together with simultaneous hydrogen peroxide production of 366 μmol g−1 h−1 under environmentally friendly neutral conditions. Intriguingly, the addition of tetracycline hydrochloride can accelerate hydrogen peroxide generation, which thus in turn speed up tetracycline hydrochloride degradation. It was revealed that the optimized electronic structure, promoted light-harvesting, and enhanced charge carriers separation capacity are conducive for the synchronous oxygen reduction and contaminant oxidation procedure in large measure. Furthermore, the degradation and hydrogen peroxide generation can be maintained even after 15 cycles, demonstrating the stability of OSCN and its possibility for practical applications. The degradation pathway and in-deep reaction mechanism are carried out accordingly. Additionally, such a synchronously promoted reaction can be extended to some other pollutants, like phenol and 2,4-dichlorophenol. This interesting work provides a novel strategy for pollutants removal and concurrent hydrogen peroxide generation. Carbon nitride with abundant edge and basal active sites through non-metallic element doping was synthesized for photocatalytic hydrogen peroxide formation together with the synergistic treatment of tetracycline hydrochloride. Furthermore, it is revealed that the addition of tetracycline hydrochloride (TH) accelerates the production of hydrogen peroxide, and in turn, hydrogen peroxide accelerates the degradation of TH under neutral conditions. [Display omitted] • Doped carbon nitride with abundant edge and basal active sites was synthesized. • OSCN was utilized for TH removal and synergistic H 2 O 2 photosynthesis. • The addition of TH promotes H 2 O 2 production, while H 2 O 2 accelerates TH degradation. • The photocatalytic performance could be maintained even after 15 cycles. [ABSTRACT FROM AUTHOR]

The photocatalytic fuel cell (PFC) synergistically utilizes the photocatalytic oxidation of biomass and the electrochemical reaction of the fuel cell to selectively reduce oxygen to produce hydrogen peroxide (H2O2) at room temperature. Herein, we report a PEC system that NiFe-layered double oxide (LDO)/TiO2 as photoanode, carbon black as cathode for utilizing biomass and oxygen to simultaneously convert solar energy into electricity and produce hydrogen peroxide without applied electric bias. The photoanode catalyst was fabricated with TiO2-supported NiFe mixed metal oxides (MMO) which obtained by layered double hydroxides (LDHs) pyrolysis. The research results indicate that under solar irradiation, the photocurrent density and faraday efficiency have a significantly improved compared with pure NiO/TiO2. With methanol as the feeding fuel at the photoanode, the optimal device yields an excellent open circuit voltage (Voc), short circuit current (Jsc) and a maximum power density (Pmax) of 0.78 V, 1093 μA/cm² and 169 μW/cm², respectively. This performance improvement is attributed to the Fe3+ doped in NiFe-MMO and use TiO2 as an electron transport layer. Simultaneously, the hydrogen peroxide concentration reached 0.443 mM after 180 min illumination at the cathode, the generation rate was optimized to 0.126 μmol/min/cm² at neutral aqueous solution. The PEC system exhibited an excellent higher rate of production for H2O2, and faraday efficiency (FE) reached 31.7 %. This PFC is a green technology for photocatalytically oxidize biomass at the photoanode and convert solar energy into electricity as well as supply it to the cathode to reduce O2 to produce H2O2 efficiently. [ABSTRACT FROM AUTHOR]

Herein, a carbon felt (CF) cathode modified by the acidic oxidised carbon nanotubes (OCNTs) exhibited a high yield of the H 2 O 2 generation in electro-Fenton. Rotating disk electrode (RDE) measurements showed that the selective generation of H 2 O 2 occurred on the CF cathode coated by OCNTs (OCNTs/CF), which was attributed to the high amount of oxygen-containing functional groups in OCNTs. Moreover, the pollutant degradation efficiency could almost reach 100% within 60 min in electro-Fenton with OCNTs/CF as the cathode. Furthermore, the pollutant removal efficiency was kept constant after five consecutive cycles, indicating the high stability of OCNTs/CF cathode. Besides, the hydrophilicity of OCNTs/CF cathode was significantly enhanced owing to the abundant oxygen-contained functional groups on the surface of the OCNTs/CF cathode, which facilitated the mass transfer between the OCNTs/CF cathode and the reactants in the bulk solution. To reveal the possible mechanism in electro-Fenton equipped with the OCNTs/CF cathode, quenching experiments and electron paramagnetic resonance (EPR) investigations were further conducted. This work provided valuable insights into the fabrication of the non-metallic cathode with a high ability towards H 2 O 2 generation in electro-Fenton for efficient pollutant removal.

With light illumination, the nanoneedle structured carbon nitride would induce a "lightning rod effects" to guide charge directional migration, significantly suppressing electron-hole recombination, leading to the excellent photocatalytic performance for both H 2 evolution and H 2 O 2 production. • 3D branched carbon nitride nanoneedle has been successfully constructed. • Sharp nanoneedle shape could induce nanoscale lightning rod effect to cause electric field redistribution. • Such lightning rod effect is found to guide charge directional migration, boosting charge separation. • 3DBC-C 3 N 4 -N shows high H 2 evolution performance (AQY: 27% @420 nm) and H 2 O 2 production. Polymeric materials are promising photocatalysts for clean energy (e.g. hydrogen) production, however their catalytic performances are largely restricted to the low charge mobility and sluggish electron-hole separation efficiency. Herein, we propose a novel three dimensional (3D) branched carbon nitride integrated by one dimensional (1D) nanoneedles (3DBC-C3N4-N) to overcome this obstacle. We verify that the integrated crystalline nanoneedles with high curvature tips could induce a "lightning rod effect" property to accelerate charge transfer and separation by guiding electron migration along the sharp tip direction. Both 3D finite-difference time-domain (FDTD) calculation and experimental results reveal that the high curvature crystalline tip can intensify the local electric intensity by concentrating the photogenerated electrons around the tip area, therefore significantly enhance electron-hole separation. As a result, the 3DBC-C3N4-N exhibits excellent visible light (λ > 420 nm) photocatalytic H2O2 production as well as H2 evolution performance with obvious bubbles bubble out from the surface of catalyst and a notable apparent quantum efficiency (AQE) of 26% at 420 nm, higher than most reported polymeric materials. The innovative "lightning rod effect" strategy described here shows great potential to manipulate charge transfer and separation process for achieving efficient solar energy conversion. [ABSTRACT FROM AUTHOR]

• A packed bed electro-Fenton system with in-situ H 2 O 2 generation was developed. • The set-up with carbon electrodes achieved 100% p -nitrophenol removal in two hours. • p -nitrophenol removal was affected by pH, applied current and air sparging rate. • Mineralization of intermediates was confirmed by GC–MS, COD and TOC reduction. • Overall, in-situ H 2 O 2 production reduced chemical consumption and sludge generation. Advancements in electrochemical generation of hydrogen peroxide (H 2 O 2) in Fenton systems hasten the realization of a "chemical-free" treatment of organic pollutants in water. The present study used a novel air-sparged, packed-bed electrode configuration with reticulated vitreous carbon (RVC) as packing material for electrochemical H 2 O 2 generation. The effects of initial pH, applied current, sparging rate, mass of RVC and electrolyte concentration on cumulative H 2 O 2 generation and current efficiency were evaluated. From the results, the operating conditions that gave the optimal cumulative H 2 O 2 generation and current efficiency were pH 0 = 2.0, applied current = 50 mA, air sparging rate = 0.5 L min−1, mass of RVC = 0.75 g, and electrolyte concentration = 100 mM Na 2 SO 4. The same reactor configuration was used for the treatment of the model contaminant from aqueous solution and caused the complete removal of p -nitrophenol (p nP) within a 2 h duration. Mineralization of aromatic intermediates was confirmed by gas chromatography – mass spectroscopy analyses of samples and supported by the reduction in chemical oxygen demand and total organic carbon. [ABSTRACT FROM AUTHOR]

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We report a facile one-pot aqueous-phase synthesis of PdAu bimetallic nanoparticles with different Pd/Au ratio. The synthesis was conducted by co-reduction of Pd and Au precursor using ascorbic acid as a reducing agent and in the presence of polyallylamine hydrochloride (PAH). By high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectrometry (EDS) analyses, we found that the synthesized nanoparticles had an onion-like core/shell/shell/shell structure with Au-rich core, Pd-rich shell, Au-rich shell, and Pd shell, respectively. We also investigated the catalytic performance of the synthesized PdAu nanoparticles toward hydrogen peroxide generation reaction. [ABSTRACT FROM AUTHOR]

The incineration of plastics and biomass is an efficient alternative to reduce the amount of solid waste and is also beneficial for energy production. Soot is one of the main byproducts generated during solid waste incineration, and so far, it has been treated as a pollutant. However, soot is an interesting nanostructured material displaying high specific surface area and chemical reactivity. In this work, soot produced by incomplete burning of plastic materials was combined with polymer nanofibers resulting in a multifunctional membrane explored for pollutant adsorption, sensing of organic pollutants, and in the electrogeneration of hydrogen peroxide. Specifically, soot was immobilized onto polyamide 6 nanofibrous membranes (NFM) produced by solution blow spinning following two different approaches: pre-synthesis and post-synthesis modification, and then the effect of soot chemical activation with NaOH was investigated. The adsorption tests showed that the chemical activation was essential to increase efficiency by improving its hydrophilicity and generation of adsorption sites. The experimental and calculated batch adsorption efficiency towards methylene blue was 94.33 mg/g and 37.71 mg/g, respectively. The adsorption efficiency in the fixed bed was 8.00 mg/g. The functional NFMs maintained their efficiency for at least ten adsorption cycles, increasing their economic viability. Furthermore, the NFMs were applied as flexible and free-standing electrodes for detecting methylene blue with a limit of detection of 2.4 nmol/L. The average per-electrode cost was estimated to be US$0.04. Finally, the NFM also demonstrated the ability to generate H 2 O 2 in situ. Altogether, these results suggest that the immobilization of soot onto nanofibrous membranes is an efficient strategy for developing multifunctional and sustainable materials towards environmental applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Objective: To identify and characterize a novel bacterial pyranose 2-oxidase (P2Ox) and investigate its potential use in lignin degradation applications.Results: A new bacterial P2Ox (PaP2Ox) enzyme was identified in the lignocellulolytic bacterium Pantoea ananatis Sd-1. The PaP2Ox open reading frame was cloned, and the encoded protein was heterologously expressed in an Escherichia coli expression system. Unlike another reported bacterial P2Ox enzyme, the purified PaP2Ox exhibits a homotetrameric spatial conformation that is similar to fungal P2Oxs, with each subunit having a molecular mass of 65 kDa. The recombinant PaP2Ox exhibits maximum activity at 50 °C and pH 6.5 with d-glucose as its preferred substrate. In addition, this enzyme was shown to work in combination with bacterial laccase in lignin degradation.Conclusions: The bacterial enzyme PaP2Ox has potential use in ligninolytic systems and shows promising value in industrial biotechnological applications. [ABSTRACT FROM AUTHOR]

Intratumoral injections can reduce systemic absorption and deliver large amounts of drugs to the tumor, thereby reducing side effects and exhibiting high therapeutic efficacy. Therefore, a variety of drug delivery systems, such as hydrogels, fine particles, and nanoparticles, have been studied. Although the sustained-release drug delivery system can effectively reduce systemic absorption due to the slow release of the drug from the site of intratumoral injection, it lacks the ability to deliver high concentrations of drugs to the tumor. In particular, the larger the tumor size, the lower the efficacy of the treatment. To address this problem, this study focused on the tumor structure. Owing to the three-dimensional structure of the dense tumor microenvironment (TME) and abnormal blood vessels, drugs administered directly into the tumor act as if they were encapsulated in a hydrogel. To evaluate whether the three-dimensional structure of the tumor affects the intratumoral distribution and systemic absorption of drugs, needle-type starch implants (GOD-NS implants) and needle-type gelatin implants (GOD-NG implants) containing glucose oxidase (GOD), a protein that exhibits anti-cancer effects through hydrogen peroxide (H 2 O 2) generation, were prepared. Both GOD-NS and GOD-NG implants can be easily injected into tumors. GOD-NS implants released GOD slowly, whereas GOD-NG implants released most of the GOD within 1 h. When a GOD-NG implant that rapidly released GOD was also injected, a high concentration of GOD was maintained in the tumor for a long time as it was trapped in the three-dimensional structure of the tumor. This study demonstrated that intratumoral injection of a rapidly drug-releasing gelatin needle may be a novel drug delivery system capable of long-term retention of high drug concentrations in tumors, as the three-dimensional structure of the tumor affects drug delivery. • •High-dose drug administration may cause toxicity due to systemic absorption. • The tumor's dense ECM and abnormal blood vessels can act as a barrier to drug leakage. • Rapidly-dissolving NG implants can deliver higher concentrations of drugs to the tumor. [ABSTRACT FROM AUTHOR]

This work aimed at exploring the effect of optimal overpotential discrepancy between two-electron oxygen reduction reaction (OP 2eORR) and metal reduction reaction (OP MRR) of the cathode on electro-Fenton (EF) system performance, and proposing strategy to eliminate overpotential discrepancy. Therefore, series of vanadium-doped chitosan carbon aerogel (xCCA-V) cathodes were fabricated by controlling graphitization degree. With carbonized temperature of 900 °C, the OP 2eORR of the 900CCA-V was −0.5 V vs. SCE, the same with the OP for vanadium reduction reaction (OP VRR). This identical OP of the 900CCA-V endowed excellent EF performance, with ciprofloxacin removal of 98.1%, and TOC removal significantly increased by 41.8% compared with Ferrum-doped CCA (900CCA-Fe). Density functional theory calculation revealed efficient active sites for H 2 O 2 adsorption on the 900CCA-V surface. Degradation pathways of ciprofloxacin and intermediates toxicity were determined. This work provides inspiration for developing strategy for overpotential regulation and design novel and efficient cathodes for enhancing EF performance. [Display omitted] • The efficient V-doped chitosan carbon aerogel cathode was developed for EF. • Regulating overpotential for H 2 O 2 generation and V reduction enhanced performance. • H 2 O 2 adsorption sites on VN (200) was discussed by DFT calculations. • Ciprofloxacin degradation mechanism and intermediates' ecotoxicity were studied. [ABSTRACT FROM AUTHOR]

This paper presents results on electric discharge generation by high frequency high voltage (15–100 kHz) in NaCl solutions with different initial conductivity (100–1300 mS cm-1), and compares them with DC discharge in the same electrode configuration. A batch plasma reactor in the pin-hole configuration contained a ceramic dielectric barrier separating two planar stainless steel electrodes; barrier thickness of 0.6 mm and pin-hole diameter of 0.6 mm was used. Lissajous charts were evaluated from electric measurements for different discharge phases (electrolysis, bubble formation and discharge regular operation). Breakdown moments for different solution conductivities were determined from discharge power evaluation as a function of applied frequency. Breakdown voltage amplitude was decreased by the increasing conductivity in both regimes while frequency and current decreased. Changes of physical parameters (temperature, solution conductivity and pH) as well as production of hydrogen peroxide at different solution conductivities were compared. Solution conductivity was increased in both discharge regimes and with the initial conductivity value. Solution temperature was increased by the discharge in both regimes and with the increasing initial conductivity, too. Solution pH dropped to acidic conditions when HF or DC positive regime was applied while it was enhanced by DC negative regime.

This work presents a novel method for oxidation of organic matter in water solutions based on catalytic membrane reactors. The oxidant, hydrogen peroxide, is generated directly in the bulk of the liquid investigated. Commercial symmetric alumina hollow fibers have been used as a starting material thereafter introducing the active phases. It has been proven that two different catalysts are necessary in order to complete the overall reaction, as well as to generate hydrogen peroxide and a heterogeneous Fenton process. Palladium has been used for the hydrogen peroxide generation and a second active phase, transitional metal oxides or homogeneous Fe 2+ , has been used for the hydroxyl radical generation. An additional method for specific Pd loading to the reaction zone based on sputtering technique has been developed. All prepared catalytic membrane reactors (CMRs) are capable of generating hydrogen peroxide in amounts comparable to CMRs reported in the literature. The catalytic membrane reactors prepared by Pd impregnation show very high activity and stability in phenol oxidation reaching 40% of the generated H 2 O 2 usage in the oxidation reaction. Despite the very high activity of the catalytic membrane reactors obtained by Pd sputtering in H 2 O 2 production they suffer very fast deactivation. Specific reactivation including a calcination step has been found to be appropriate for the recovery of their activity. Additional experiments give new insights for better understanding of Pd deactivation especially when the metal particles are of nanometer sizes. [ABSTRACT FROM AUTHOR]

This paper presents results on electric discharge generation by high frequency high voltage (15-100 kHz) in NaCl solutions with different initial conductivity (100-1300 mS cm-1), and compares them with DC discharge in the same electrode configuration. A batch plasma reactor in the pin-hole configuration contained a ceramic dielectric barrier separating two planar stainless steel electrodes; barrier thickness of 0.6 mm and pin-hole diameter of 0.6 mm was used. Lissajous charts were evaluated from electric measurements for different discharge phases (electrolysis, bubble formation and discharge regular operation). Breakdown moments for different solution conductivities were determined from discharge power evaluation as a function of applied frequency. Breakdown voltage amplitude was decreased by the increasing conductivity in both regimes while frequency and current decreased. Changes of physical parameters (temperature, solution conductivity and pH) as well as production of hydrogen peroxide at different solution conductivities were compared. Solution conductivity was increased in both discharge regimes and with the initial conductivity value. Solution temperature was increased by the discharge in both regimes and with the increasing initial conductivity, too. Solution pH dropped to acidic conditions when HF or DC positive regime was applied while it was enhanced by DC negative regime. [ABSTRACT FROM AUTHOR]

Piezocatalysis is capable of converting mechanical vibrations into chemical energy, portraying a promising alternative technology for hydrogen peroxide (H 2 O 2) production. Environmentally benign lead-free barium titanate piezocatalyst has received particular attention due to its ferroelectric property. However, the reported H 2 O 2 yield is not ideal and one of the reasons is the undesirable piezoelectricity. Herein, a series of lead-free perovskite oxides consisting of (1-x)Ba(Zr 0.2 Ti 0.8)O 3 –x(Ba 0.7 Ca 0.3)TiO 3 solid solutions are developed for H 2 O 2 production by introducing more favorable crystal phases to increase the piezoelectricity. The prepared perovskite oxides were characterized by significantly enhanced piezoeletricities owing to the coexistence of the ternary (orthorhombic, tetragonal and rhombohedral) phases with reduced energy barrier for polarization rotation. Benefiting from the notably improved piezoelectric property and appropriate oxygen vacancy concentration, the optimal composition of 0.5Ba(Zr 0.2 Ti 0.8)O 3 –0.5(Ba 0.7 Ca 0.3)TiO 3 exhibits an outstanding H 2 O 2 selective generation and long-lasting stability. Under ultrasonic irradiation, a superior H 2 O 2 yield of 692 µmol g-1 h-1 with a selectivity of 80% was attained, showing the enhancement by the factors of 3.3, 4.1 and 8.7 compared to Ba 0.7 Ca 0.3 TiO 3 , BaZr 0.2 Ti 0.8 O 3 and BaTiO 3 , respectively. Furthermore, the catalyst is highly stable by delivering a H 2 O 2 productivity of 3313 µmol g-1 in 14 h of piezocatalysis. Mechanism study suggests that H 2 O 2 generation stems from an efficient O 2 reduction via a two-electron transfer pathway, during which the piezopotential is of primary importance to provide driving force for the carrier separation and transportation. Moreover, the green and non-toxic piezocatalysis system based on the BaCaZrTi solid solutions can be applied for efficient water disinfection. This study offers guidance towards the rational design of lead-free piezocatalyst and reaction system for H 2 O 2 generation and its application. [Display omitted] • Piezocatalysts of BaCaZrTi solid solutions with ternary phases were prepared. • The superior activity and high stability of piezocatalytic H 2 O 2 generation over BCZT-0.5 were achieved. • The reaction mechanism and the enhancement of piezocatalytic activity were revealed. • Application of the piezocatalysis system over BCZT-x is exemplified for efficient sterilization. [ABSTRACT FROM AUTHOR]

• Electrochemical study of NDXT. • Modification of the glassy carbon electrode with NDXT. • Electrocatalytic generation of hydrogen peroxide. • Optimization of effective parameters on H 2 O 2 production. This work consists of three parts: in the first part, the electrochemical characteristics of 13-(4-nitrophenyl)-5 H -dibenzo[b,i]xanthene-5,7,12,14(13 H)-tetraone (NDXT), a newly synthesized compound was investigated in water/DMF solution using cyclic voltammetry, double potential step chronoamperometry and differential pulse voltammetry techniques. Based on the data obtained at this stage, a plausible mechanism for electrochemical behavior of NDXT was proposed. In the second part, the modification of the glassy carbon and carbon electrodes with NDXT was studied by different electrochemical techniques. In this part, the best conditions for covalent immobilization of NDXT on the electrode surface were determined and the immobilization mechanism of NDXT was discussed. Based on the results obtained at this stage, the modification of GC electrode was performed in a solution of NDXT and KNO 2 in water (H 2 SO 4 , 1.2 M)/DMF (30/70, v/v) using cyclic voltammetry with a scan rate of 300 mV/s for 10 cycles between -0.1 and -1.0 V. In the third part, the electrochemical generation of H 2 O 2 using modified NDXT carbon electrode, by reduction of dissolved O 2 was studied. The results show that the modified cathode has good electrocatalytic activity in the production of hydrogen peroxide (461 mg/L). The effective parameters on the production of H 2 O 2 including, current density, pH and cell design have been optimized. In this work, we developed a facile method for the electrocatalytic generation of hydrogen peroxide without using the metal catalyst, external H 2 source and liquid-liquid extraction step which is a major improvement in comparison to the industrial anthraquinone based method. A green, metal-free and efficient method for hydrogen peroxide generation using carbon electrode modified with a new derivative of 5 H -dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraone was developed. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel binder-free anthraquinone (AQS)/polyaniline (PANI) modified carbon felt (CF) cathode for selective H 2 O 2 generation and efficient pollutant removal in electro-Fenton was fabricated by CV electro-deposition method. AQS, the oxygen reduction reaction (ORR) catalyst, was immobilized by the PANI film, which contributed to the obtained high stability of the AQS/PANI@CF cathode. The concentration of the electro-generated H 2 O 2 on AQS/PANI@CF cathode (83.3 μmol L−1) was about 10 times higher than that of the bare CF cathode. And the high yield of H 2 O 2 was attributed to the catalytic reduction of O 2 by AQS to generate more superoxide radical (O 2 •-), which combined with H+ to form H 2 O 2. Additionally, the rhodamine B (RhB) degradation efficiency reached 98.8% within 60 min with the AQS/PANI@CF served as the cathode with high stability and good repeatability. The main generated reactive radicals were determined by the quenching experiments and the electron paramagnetic resonance (EPR) tests. Besides, a plausible mechanism of the AQS/PANI@CF cathode applied electro-Fenton process was proposed. This work provided a reliable reference for the subsequent investigations of the binder-free cathode with high performance and stability. [Display omitted] • A novel anthraquinone/polyaniline coated carbon felt (AQS/PANI@CF) was prepared. • The AQS/PANI@CF cathode could enhance the yield of the electro-generated H 2 O 2. • The AQS/PANI@CF cathode has high performance and stability in electro-Fenton. • Mechanism of the AQS/PANI@CF cathode applied in electro-Fenton was proposed. [ABSTRACT FROM AUTHOR]