Study on oxidative degradation behaviors of polyesterurethane network

In this study H₂O₂/CoCl₂ system was used as an oxidative environment to investigate the in vitro degradation behavior of a crosslinked polyesterurethane network. Weight loss, water absorption, mechanical properties, swelling degree and gel content were determined as a function of degradation time. The results showed that the H₂O₂/CoCl₂ system could effectively accelerate the degradation of the polyurethanes. The samples had almost completely degraded after 84 days of incubation in a 3% H₂O₂/2% CoCl₂ solution at 37 °C. The weight loss process could be approximately divided into three major phases: the weight decreased slowly during an induction phase (1), which was followed by a phase characterized by accelerated weight loss (2), and finally by a phase showing slow linear weight loss until complete erosion (3). The attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra of degraded polyurethane networks showed that the polyurethane underwent chain scission of the copolyester segment chains, and the joints of copolyester and 2,2,4- and 2,4,4-trimethylhexamethylene during degradation in the oxidative environment. The glass transition temperature of degraded polyesterurethane networks decreased significantly with increasing degradation time. From these results the H₂O₂/CoCl₂ system can be used as an oxidative condition to evaluate the in vitro degradability of polyesterurethane.     

A Highly Selective and Sensitive Chemiluminescent Probe for Real-Time Monitoring of Hydrogen Peroxide in Cells and Animals

Selective and sensitive molecular probes for hydrogen peroxide (H₂O₂), which plays diverse roles in oxidative stress and redox signaling, are urgently needed to investigate the physiological and pathological effects of H₂O₂. A lack of reliable tools for in vivo imaging has hampered the development of H₂O₂ mediated therapeutics. By combining a specific tandem Payne/Dakin reaction with a chemiluminescent scaffold, H₂O₂-CL-510 was developed as a highly selective and sensitive probe for detection of H₂O₂ both in vitro and in vivo. A rapid 430-fold enhancement of chemiluminescence was triggered directly by H₂O₂ without any laser excitation. Arsenic trioxide induced oxidative damage in leukemia was successfully detected. In particular, cerebral ischemia-reperfusion injury-induced H₂O₂ fluxes were visualized in rat brains using H₂O₂-CL-510 , providing a new chemical tool for real-time monitoring of H₂O₂ dynamics in living animals.     

A Highly Selective and Sensitive Chemiluminescent Probe for Real‐Time Monitoring of Hydrogen Peroxide in Cells and Animals

Selective and sensitive molecular probes for hydrogen peroxide (H₂O₂), which plays diverse roles in oxidative stress and redox signaling, are urgently needed to investigate the physiological and pathological effects of H₂O₂. A lack of reliable tools for in vivo imaging has hampered the development of H₂O₂ mediated therapeutics. By combining a specific tandem Payne/Dakin reaction with a chemiluminescent scaffold, H₂O₂‐CL‐510 was developed as a highly selective and sensitive probe for detection of H₂O₂ both in vitro and in vivo. A rapid 430‐fold enhancement of chemiluminescence was triggered directly by H₂O₂ without any laser excitation. Arsenic trioxide induced oxidative damage in leukemia was successfully detected. In particular, cerebral ischemia‐reperfusion injury‐induced H₂O₂ fluxes were visualized in rat brains using H₂O₂‐CL‐510 , providing a new chemical tool for real‐time monitoring of H₂O₂ dynamics in living animals.     

Fluorescent probes for in vitro and in vivo quantification of hydrogen peroxide

Hydrogen peroxide (H₂O₂) plays essential roles in redox signaling and oxidative stress, and its dynamic concentration is critical to human health and diseases. Here we report the design, syntheses, and biological applications of HKPerox-Red and HKPerox-Ratio for quantitative measurement of H₂O₂. Both probes were successfully applied to detect endogenous H₂O₂ fluxes in living cells or zebrafish, and biological effects of multiple stress inducers including rotenone, arsenic trioxide, and starvation were investigated. As H₂O₂ is a common by-product for oxidase oxidation, a general assay was developed for ultrasensitive detection of various metabolites (glucose, uric acid, and sarcosine). Moreover, cellular H₂O₂ measurements were achieved for the first time by combining flow cytometry with live cell calibration. This study provides a pair of unique molecular tools for advanced H₂O₂ bio-imaging and assay development.

New class of H₂O₂ probes, HKPerox-Red and HKPerox-Ratio, were developed for quantitative measurement of H₂O₂ generated in multiple disease models using bio-imaging, flow cytometry, and in vitro assays in an ultra-sensitive and selective manner.     

Relationship between Neuroprotective Effects and Structure of Procyanidins

This study evaluated the relationship between the neuroprotective effects of procyanidins and their structural characteristics. In vitro, a rat pheochromocytoma cell line (PC12) was exposed to the grape seed-derived procyanidin monomers: catechin (C), epicatechin (EC), and epicatechin gallate (ECG); the procyanidin dimers: procyanidin B1 (B1), procyanidin B2 (B2), procyanidin B3 (B3), procyanidin B4 (B4), procyanidin B1-3-O-gallate (B1-G), and procyanidin B2-3-O-gallate (B2-G); and the procyanidin trimers: procyanidin C1 (C1) and N-acetyl-l-cysteine (NAC) for 24 h. Cells were then incubated with 200 μM H₂O₂ for 24 h. In vivo, zebrafish larvae (AB strain) 3 days post-fertilization were incubated with NAC or procyanidins (C, EC, ECG, B1, B2, B3, B4, B1-G, B2-G, C1) in 300 µM H₂O₂ for 4 days. Different grape seed procyanidins increased the survival of PC12 cells challenged with H₂O₂, improved the movement behavior disorder of zebrafish caused by H₂O₂, inhibited the increase of ROS and MDA and the decrease of GSH-Px, CAT, and SOD activities, and up-regulated the Nrf2/ARE pathway. The neuroprotective effects of the procyanidin trimer C1 treatment group were greater than the other treatment groups. These results suggest that the neuroprotective effect of procyanidins is positively correlated with their degree of polymerization.     

Effects of cationic and anionic micelles on the redox reaction of Erythrosine B by H2O2 in presence of Cu-Fe nanoparticles

Kinetic investigation of the degradation of Erythrosine B (EB) by H₂O₂ and copper-iron bimetallic nanoparticles was carried out spectrophotometrically. The degradation was carried out under the condition of sonication at 40°C. The co-precipitation method was used for the fabrication of CuO/Fe₂O₃ (Cu-Fe) in an alkaline solution and characterized by SEM, XRD, FTIR, TEM, EDS, and BET methods. In the absence of the Cu-Fe, no degradation of EB by H₂O₂ was observed. The presence of Cu-Fe resulted into the degradation of EB by H₂O₂. The kinetics of the degradation was studied under the conditions of variation of the amount of nanoparticles and at different concentrations of EB, H₂O₂, H⁺, surfactants (sodium dodecyl sulphate; SDS and cetyltrimethylammonium bromide; CTABr). The rate of reaction depends on the amount of Cu-Fe and [H₂O₂]. The rate constant values gave the peaked like curve (with maximum value at pH 3) at different pH. The dye degradation decreased with the increase in presence of (SDS) and (CTABr).     

Construction of two Novel 2D Coordination Frameworks with the Ligand H3nbtc: Synthesis,Crystal Structures,and Luminescence

Two novel 2D coordination polymers, namely, {[Cu₂(L)₂][Cu(H₂O)₃]}_n ( 1 ) and {Pb₃(O₂N‐btb)₂}_n ( 2 ) (O₂N‐H₃btb = 5‐nitro‐benzene‐1, 2, 3‐tricarboxylic acid, L = 5‐nitro‐2‐oxidoisophthalate), were synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, X‐ray diffraction, and thermogravimetric analysis. Compound 1 is an infinite 2D layer exhibiting an extended 3D supramolecular network structure. O–H ··· O hydrogen bonding interactions play a key role in forming the final 3D supramolecular framework. It is noted that 5‐nitro‐benzene‐1, 2, 3‐tricarboxylic acid (O₂N‐H₃btb) was in situ transformed to 5‐nitro‐2‐oxidoisophthalate in 1 . Compound 2 is a 2D microporous lead‐containing metal‐organic framework made up of interconnected Pb‐carboxylate chains, involving three independent lead atoms with three different coordination arrangements. Furthermore, the solid‐state photoluminescence and lifetime characteristics of 2 reveal intense blue luminescence.     

In vitro antioxidant/prooxidant effects of combined use of flavonoids

The present study was undertaken to investigate the individual and combined antioxidant or prooxidant effects of genistein, daidzein and quercetin in human erythrocytes and rat microsomes in vitro. Their reducing potential against oxidation of a redox sensitive fluorescent probe, their protective effect against H₂O₂-induced membrane lipid peroxidation and their inhibitory effect on AAPH-induced hemolysis were evaluated. Genistein and daidzein were prooxidant in erythrocytes but antioxidant in microsomes where their metabolites might have been formed which suggests the importance of metabolic capacity in in vitro models to predict the physiological situation. Quercetin showed antioxidant effects in all models and conditions. Prooxidant effect of ‘genistein–daidzein mixture’, at their concentrations reflecting the real life, was suppressed by addition of quercetin to the mixture. Our study shows that flavonoids can exert prooxidant effects depending on the conditions, but the mixture effect should be considered while assessing their effects and safety in humans.     

Removal and mineralization of toluene under VUV/UV lamp irradiation in humid air: Effect of light wavelength,O2 and H2O

VUV/UV photodegradation is a promising method that utilizes energetic photons and reactive oxygen species (ROS) generated via the photo-dissociation of H₂O and O₂ to degrade VOCs. In the paper, we investigated the efficiency of removal and mineralization in humid air and the effects of key factors. Toluene of 4–20 ppm can be almost completely removed in 60 s and mineralization efficiency is above 55% at 25 min. 185 nm ultraviolet light plays a key role in the rapid removal and mineralization of toluene. Appropriate amount of O₂ and H₂O promote the removal of toluene due to the generation of ROS. Based on the intermediates and degradation pathway analysis, it is found that in the presence of O₂, degradation pathways of toluene are more abundant and fewer linear-chain aldehydes are produced, thus resulting in higher mineralization efficiency. This work highlights the importance of practical application of VUV/UV photodegradation in humid air.     

Fenton’s reagent-mediated degradation of residual Kraft black liquor

In this work, the effect of Fento’s reagent on the degradation of residual Kraft black liquor was investigated. The effect of Fenton’s reagent on the black liquor degradation was dependent on the concentration of H₂O₂. At low concentrations (5 and 15 mM) of H₂O₂, Fenton’s reagent caused the degradation of phenolic groups (6.8 and 44.8%, respectively), the reduction of reaction medium pH (18.2%), and the polymerization of black liquor lignin. At a high concentration (60 mM) of H₂O₂, Fenton’s reagent induced an extensive degradation of lignin (95–100%) and discoloration of the black liquor. In the presence of traces of iron, the addition of H₂O₂ alone induced mainly lignin fragmentation. In conclusion, Fenton’s reagent and H₂O₂ alone can degrade residual Kraft black liquor under acidic conditions at room temperature.     

Magnesium Corrosion Triggered Spontaneous Generation of H2O2 on Oxidized Titanium for Promoting Angiogenesis

Although the use of reactive oxygen species (ROS) has been extensively studied, current systems employ external stimuli such as light or electrical energy to produce ROS, which limits their practical usage. In this report, biocompatible metals were used to construct a novel electrochemical system that can spontaneously generate H₂O₂ without any external light or voltage. The corrosion of Mg transfers electrons to Au‐decorated oxidized Ti in an energetically favorable process, and the spontaneous generation of H₂O₂ in an oxygen reduction reaction was revealed to occur at titanium by combined spectroscopic and electrochemical analyses. The controlled release of H₂O₂ noticeably enhanced in vitro angiogenesis even in the absence of growth factors. Finally, a new titanium implant prototype was developed by Mg incorporation, and its potential for promoting angiogenesis was demonstrated.     

In vitro and in vivo degradation of an injectable bone repair composite

In vitro and in vivo degradation behaviors of an injectable bone regeneration composite (IBRC) which comprised of nano-hydroxyapatite/collagen (nHAC) particles in alginate hydrogel carrier were investigated. In vitro degradation quantitative testing indicated that the alginate had a faster degradation rate in simulated body fluid (SBF) than in deionized water at 37 °C. Similarly, IBRC also had a higher degradation rate in SBF than in deionized water at 37 °C, which was evaluated by alginate molecular weight measurement, mechanical properties test and degradation kinetics evaluation. But molecular weight of alginate degraded slower in IBRC than that in aqueous solution. In vitro results showed that degradation medium SBF had influence on degradation of alginate molecules. In the in vivo degradation study, surprisingly, there was no obvious decreasing of molecular weight of alginate from 0 to 8 weeks. IBRC degraded mostly after 24 weeks implantation and was replaced by connective tissue. No fibrous capsule and acute inflammatory reaction were found during the observed 24 weeks after IBRC implantation. There is only a mild short-term inflammatory response in rat dorsum muscle. These results indicated that IBRC had a controllable degradability and biocompatibility. Therefore, IBRC may be a promising degradable material for bone repair and bone tissue engineering.     

4-Chlorophenol Degradation and Hydrogen Peroxide Formation Induced by DC Diaphragm Glow Discharge in an Aqueous Solution

In the present study, formation of hydrogen peroxide (H₂O₂) and degradation of 4-chlorophenol (4-CP) induced by DC diaphragm glow discharge (DGD) in a sodium sulfate solution were investigated. The discharge was generated in a small hole on a quarts plate interposed between two submersed graphite electrodes. Experimental results showed that 750 V was the optimum voltage for H₂O₂ formation and 4-CP degradation. Both the H₂O₂ formation and the 4-CP degradation proceeded faster in cathodic compartment than in anodic compartment. Lowering the solution pH was favorable for 4-CP degradation but showed no appreciable effect on H₂O₂ formation. Addition of hydroxyl radical scavenger (methanol) to the solution decreased the H₂O₂ formation and the 4-CP degradation. Iron species especially ferric ions enhanced the 4-CP degradation markedly. Based on the analyzes of Current–Voltage characteristics and chemical effects, it was deduced that the mechanism of DGD was similar to that of contact glow discharge electrolysis.     

Degradation of phenylarsonic acid and its derivatives into arsenate by hydrothermal treatment and photocatalytic reaction

The degradation of phenylarsonic acid (PA) and its derivatives by hydrothermal treatment (HTT) was examined, especially focusing on the effect of adding H₂O₂ upon the degradation efficiency. The degradation was assessed by the generation of arsenate resulting from the cleavage of As C bonds in the PA derivatives. When PA (without substituents) was subjected to an HTT with H₂O₂ (H₂O₂‐HTT; 0.5–1% H₂O₂) at 175–200 °C, PA was almost completely degraded into arsenate, whereas an HTT with NaOH (NaOH‐HTT; 3 M NaOH) at the temperatures provided almost no degradation. The H₂O₂‐HTT also worked well for the degradation of PA derivatives with hydroxy and/or nitro groups on the phenyl ring. However, the degradation of aminophenylarsonic acids was not favorably performed by the H₂O₂‐HTT. The effect of the structure of PA derivatives upon the degradation susceptibility was discussed. A photocatalytic reaction using TiO₂ was also attempted for the degradation of PA derivatives. Copyright © 2005 John Wiley & Sons, Ltd.     

Degradation of perfluorinated sulfonic acid films: An in-situ infrared spectro-electrochemical study

The in-situ Fourier transform infrared (FTIR) spectro-electrochemical method was used to evaluate the degradation mechanism of perfluorinated sulfonic acid (PFSA) polymer for the first time. The effect of H₂O₂ concentration in Fenton's reagent on the PFSA film degradation was studied. It was found that the effect of the H₂O₂ concentration on the chemical degradation of the PFSA film was limited, whereas, the electrochemical degradation was obviously enhanced at higher H₂O₂ concentrations. The chemical degradation of PFSA film in Fenton's reagent was similar to that in pure H₂O₂ solution. However, the results indicated that the electrode potential is the dominating factor affecting the degradation of the PFSA film. It is clear that the electrochemical degradation of PFSA film in Fenton's reagent is more serious than that in pure H₂O₂ solution. Moreover, it is indicated that the main cause of the membrane degradation is the instability of the backbone of the polymer chain under electrochemical conditions and secondarily the loss of sulfuric groups in the side-chains. It is concluded that the in-situ FTIR spectro-electrochemical method could be used to evaluate more objectively the degradation of the polymer film.     

Catalytic effect of lucunary heteropolyanion containing molybdenum and tungsten atoms on decolorization of direct blue 71

In this research,a lucunary Keggin structure,[PMo₂W₉O₃₉]^7- was selected as an efficient homogenous catalyst for degradation of an azo dye（direct blue 71） and a simple method was developed for degradation of DB71.The method is based on the oxidation of azo dye in the presence of a lucunary Keggin form of polyoxometalates,K₇[PMo₂W₉O₃₉]? 19H₂O,as a homogenous catalyst at room temperature.The reaction is monitored spectrophotometrically by measuring the absorbance of dye atλ=585 nm.Some parameters including concentration of catalyst,concentration of H₂O₂,pH and reaction time were investigated and optimized. Results show that K₇[PMo₂W₉O₃₉]? 19H₂O is more efficient in the presence of hydrogen peroxide.Degradation of dye in the presence of the catalyst and H₂O₂ could lead to the disappearance approximately 65%of dye after 60 min.But degradation for the same experiment performed in the absence of catalyst or in the absence of H₂O₂ was 22%or 5%respectively.Approximately 87% azo dyes has been eliminated after 90 min in the presence of catalyst,H₂O₂ and optimize conditions(0.6 g/L of K₇[PMo_2- W₉O₃₉H₉H₂O,0.08 mol/L hydrogen peroxide and room temperature).     

Self-Immolative Amphiphilic Poly(ferrocenes) for Synergistic Amplification of Oxidative Stress in Tumor Therapy

Amphiphilic self-immolative polymers (SIPs) can achieve complete degradation solely through one triggerable event, which potentially optimize the blood clearance and uncontrollable/inert degradability for therapeutic nanoparticles. Herein, we report self-immolative amphiphilic poly(ferrocenes), BP ^nbs -Fc , composed by self-immolative backbone and aminoferrocene (AFc) side chains as well as end-capping poly(ethylene glycol) monomethyl ether. Upon triggering by tumor acidic milieu, the BP ^nbs -Fc nanoparticles readily degrade to release azaquinone methide (AQM) moieties, which can rapidly deplete intracellular glutathione (GSH) to cascade release AFc. Furthermore, both AFc and its product Fe²⁺ can catalyze intracellular hydrogen peroxide (H₂O₂) into highly reactive hydroxyl radicals (⋅OH), thus amplifying the oxidative stress of tumor cells. Rational synergy of GSH depletion and ⋅OH burst can efficiently inhibit tumor growth by the SIPs in vitro and in vivo. This work provides an elegant design to adopt innate tumor milieu-triggerable SIPs degradation to boost cellular oxidative stress, which is a promising candidate for precision medicine.     

Synthesis, characterization and in vitro oxidative stability of poly(3,3,3-trifluoropropyl)methylsiloxane modified polyurethaneurea

A series of α,ω-bis(3-hydroxypropyl)-poly[(3,3,3-trifluoropropyl)methylsiloxane] (FPS) with different molecular weights were synthesized and characterized, then the FPS modified polyurethaneurea (FSPUU) elastomers were further synthesized with poly(tetramethylene glycol)/FPS as soft segments and 4,4′-diphenylmethane diisocyanate/ethylene diamine as hard segments. The surface properties of the FSPUU films were measured. It was found that the surface hydrophobicity of these FSPUU films was enhanced with increasing the molecular weight of FPS, due to the enrichment of FPS segments at the surface region. Oxidative stability of the FSPUU films was examined in vitro by immersing the films with 200 μm thickness in oxidative solution (H₂O₂/CoCl₂) for 21 days. The experimental results showed that the degree of degradation of all FSPUU films was lower than that of polydimethylsiloxane modified polyurethaneurea (MSPUU), and the oxidative stability of these FSPUU films was fair enhanced with increasing the molecular weight of FPS, which could be attributed to the lowering of swelling ratios in H₂O and 20% H₂O₂, as well as the permeation rate of H₂O in FSPUU films. Furthermore, the tensile strength of all FSPUU films is higher than that of MSPUU film.     

Peroxidase-like activity of cytochrome c in the presence of anionic surfactants

Peroxidase-like activity of cytochrome c is significantly higher in the presence of anionic surfactants, sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and sodium n-dodecyl sulphate (SDS). The enhancement is due to the higher reaction rate of the cytochrome c with H₂O₂, which is the rate determining step in the peroxidase cycle of cytochrome c. An intermediate formed in the cycle rapidly oxidizes the substrates or reacts with further molecule(s) of H₂O₂, causing heme degradation. Thus, the specific microenvironment provided by anionic surfactants facilitates also degradation of heme iron by H₂O₂.     

Supramolecular Fluorescent Nanoparticles Constructed via Multiple Non‐Covalent Interactions for the Detection of Hydrogen Peroxide in Cancer Cells

Overabundance of hydrogen peroxide originating from environmental stress and/or genetic mutation can lead to pathological conditions. Thus, the highly sensitive detection of H₂O₂ is important. Herein, supramolecular fluorescent nanoparticles self‐assembled from fluorescein isothiocyanate modified β‐cyclodextrin (FITC‐β‐CD)/rhodamine B modified ferrocene (Fc‐RB) amphiphile were prepared through host–guest interaction between FITC‐β‐CD host and Fc‐RB guest for H₂O₂ detection in cancer cells. The self‐assembled nanoparticles based on a combination of multiple non‐covalent interactions in aqueous medium showed high sensitivity to H₂O₂ while maintaining stability under physiological condition. Owing to the fluorescence resonance energy transfer (FRET) effect, addition of H₂O₂ led to obvious fluorescence change of nanoparticles from red (RB) to green (FITC) in fluorescent experiments. In vitro study showed the fluorescent nanoparticles could be efficiently internalized by cancer cells and then disrupted by endogenous H₂O₂, accompanying with FRET from “on” to “off”. These supramolecular fluorescent nanoparticles constructed via multiple non‐covalent interactions are expected to have potential applications in diagnosis and imaging of diseases caused by oxidative stresses.