Hydroxyl radical-involved cancer therapy via Fenton reactions

The tumor microenvironment features over-expressed hydrogen peroxide(H₂O₂).Thus,versatile therapeutic strategies based on H₂O₂ as a reaction substrate to generate hydroxyl radical(?OH)have been used as a prospective therapeutic method to boost anticancer efficiency.However,the limited Fenton catalysts and insufficient endogenous H₂O₂ content in tumor sites greatly hinder?OH production,failing to achieve the desired therapeutic effect.Therefore,supplying Fenton catalysts and elevating H₂O₂ levels into cancer cells are effective strategies to improve?OH generation.These therapeutic strategies are systematically discussed in this review.Furthermore,the challenges and future developments of hydroxyl radical-involved cancer therapy are discussed to improve therapeutic efficacy.     

Pressure induced reactions amongst calcium aluminate hydrate phases

The compressibilities of two AFm phases (strätlingite and calcium hemicarboaluminate hydrate) and hydrogarnet were obtained up to 5 GPa by using synchrotron high-pressure X-ray powder diffraction with a diamond anvil cell. The AFm phases show abrupt volume contraction regardless of the molecular size of the pressure-transmitting media. This volume discontinuity could be associated to a structural transition or to the movement of the weakly bound interlayer water molecules in the AFm structure. The experimental results seem to indicate that the pressure-induced dehydration is the dominant mechanism especially with hygroscopic pressure medium. The Birch–Murnaghan equation of state was used to compute the bulk modulus of the minerals. Due to the discontinuity in the pressure–volume diagram, a two stage bulk modulus of each AFm phase was calculated. The abnormal volume compressibility for the AFm phases caused a significant change to their bulk modulus. The reliability of this experiment is verified by comparing the bulk modulus of hydrogarnet with previous studies.     

Exergetic analysis of reactions with participation of solid phases

The chemical and thermal components of exergy of solid-phase reaction systems have been analyzed. Chemical exergy is the measure of energy maintenance of chemical reaction; therefore, chemical exergy is intrinsic, not for a particular substance, but rather for a reaction mixture with a particular composition. The temperature dependence of the chemical exergy of the exothermic reaction mixture has a maximum and the temperature dependence of the chemical exergy of endothermic reaction mixture has a minimum. Equations for calculating the exergy components have been suggested, which assume the possibility of the presence of structural polymorphism for the crystal components of reaction mixture.     

Self-consistent hybrid approach for simulating electron transfer reactions in condensed phases

The recently proposed self-consistent hybrid method is presented as a numerical tool for simulating quantum dynamics in complex systems. This method is based on an iterative convergence procedure for a dynamical hybrid approach. In this approach the overall system is partitioned into a core and a reservoir. The former is treated via a numerically exact quantum mechanical method, and the latter is treated via a more approximate method. Self-consistent iterations are then carried out, with the number of core degrees of freedom and other variational parameters increased systematically to achieve numerical convergence for the overall quantum dynamics. The details of treating the core and the reservoir, as well as the convergence procedure, are discussed for several examples of electron transfer reactions in condensed phases. It is shown that the self-consistent hybrid method provides an accurate and practical way of simulating quantum dissipative dynamics in a wide range of physical regimes.     

Aqueous lipid phases of relevance to intestinal fat digestion and absorption

The phase behavior of monoglyceride/water systems, with oleic and linoleic acid as the dominating fatty acid residues, was investigated. Increased solubilization of triglycerides (oil) or oleic acid in the cubic liquid-crystalline phase formed by monoglyceride and water resulted in the formation of a reversed hexagonal liquid-crystalline phase followed by an L2-phase. The liquid-crystalline phases have different dispersion properties compared to each other in dilute micellar bile salt solutions. The cubic phase is found to be easily dispersed. The relevance of aqueous lipid phases other thah micellar is discussed in relation to intestinal lipid digestion and absorption.     

Mercury removal from coal combustion by Fenton reactions. Paper B: Pilot-scale tests

This second paper in a series describes results of pilot-scale testing for mercury (Hg) removal from coal combustion flue gas using a scrubbing solution based on the Fenton reactions. The selected reagents contain hydrogen peroxide and iron salts. The mercury scrubbing was performed in a condensing heat exchanger (CHX) with flue gas generated by coal combustion in CANMET’s vertical combustor research facility (VCRF). Both the Ontario Hydro method and a Hg CEM were used for Hg sampling and speciation. The results, obtained with the combustion of three different pulverized coals – bituminous, sub-bituminous and lignite – showed that the CHX was very effective in removing oxidized mercury (Hg(II)). Concerning the performance of the scrubbing solutions, 30–40% of elemental mercury (Hg(0)) oxidation was achieved for the lignite coal, with the solution being preferably composed of FeCl₃ and H₂O₂ and with pH value between 1 and 3. Results also showed that better Hg removal results were achieved by combining sulphur removal and Hg removal in the same stage of the CHX. An additional test done on the pilot-scale research boiler with a conventional wet scrubber showed that the Hg removal capability using the Fenton reactions was not dependent on the configuration of the wet scrubber. Although the Hg(0) oxidation ratio was not particularly high compared to the achievements from bench-scale tests, considering the economic and non-toxic nature of the scrubbing solution and the readily available equipment, the current results are encouraging and deserve further work to develop a better understanding of the chemistry in order to determine if the method can be further optimized.     

Using discrete simulation of microprocesses in dispersed phases in analyzing multiphase flows with reactions

An approach to define collisional properties and kinetic coefficients for simulating multiphase flows with reactions by integrating discrete and continuum models is developed. Accordingly, the microprocesses are investigated separately by numerical simulations of a discrete system in order to obtain information about collision frequencies, diffusion rates, etc., and then this information is incorporated into a continuous population balance model. The approach is demonstrated on a two-phase turbulent flow in a pipe type reactor where a single irreversible coalescence reaction between the identical species of the dispersed phase takes place and on diffusion of droplets in a turbulent field. A generalization of the approach to a polydispersed system of species is outlined.     

Natural antioxidants produced in oxidized lipid/amino acid browning reactions

1-Substituted pyrroles (1 and2) and1-substituted 2-(1′-hydroxypropyl)pyrroles (3–5) were produced in reactions between a lipid peroxidation product, 4,5(E)-epoxy-2(E)-heptenal, and the amino acid lysine. The antioxidative activity of compounds1–5 was studied. Oxidative stability was evaluated in refined soybean oil containing compounds1–5, butylated hydroxytoluene (BHT),n-propyl gallate orl-lysine, at concentrations of 50–200 ppm. Oils were either oxidized at 60°C and oxidation products determined by the thiobarbituric acid-reactive substances assay, or they were oxidized at 110°C by the Rancimat method. Although both methods gave similar results, greater differences were observed at 60°C than at 110°C. Addition of compounds1–5,l-lysine, BHT, and propyl gallate significantly (P<0.01) protected the oil against oxidation. The effectiveness order found was:l-lysine << compounds3–4 < compounds1–2 < compound5 ≈ BHT << propyl gallate.     

Neutral lipid composition ofCulex quinquefasciatus andCulex tritaeniorhynchus cells at two phases of growth

The mosquito cellsCulex quinquefasciatus andCulex tritaeniorhynchus were grown in spinner cultures. The fatty acid profiles of the neutral lipid classes were analyzed, and comparisons were made between the two species at logarithmic and stationary phases of growth and between the species and the medium. The results from the data suggest an increase in the average chain length of the fatty acids in the free fatty acid and sterol ester fractions of theCulex quinquefasciatus cells with aging. From the logarithmic to stationary phase, both Culex cells showed some increase in desaturation of acids in the di- and triglyceride and free fatty acid fractions. TheCulex tritaeniorhynchus cells also showed some increase in desaturation of acids in the monoglyceride fraction. Differences between the twoCulex species at the logarithmic phase of growth were observed in the fatty acid profiles of all the neutral lipid fractions examined and at the stationary phase of growth in the free fatty acid, triglyceride, and sterol ester fractions.     

Mercury removal from coal combustion by Fenton reactions – Part A: Bench-scale tests

This series of papers describes the development of technology to convert Hg(0) to Hg(II) in coal-derived flue gas based on the well-known Fenton reactions so that a Hg control strategy can be implemented in a wet scrubber. This effort consists of both bench-scale and pilot-scale work. This first paper reports on the bench-scale tests. The bench-scale results showed that Hg(0) oxidation can be achieved by the Fenton reactions and the oxidation rate is quantitatively dependent on the residence time of the Hg stream in the solution. An average of 75% oxidation of Hg(0) was achieved. Iron-based Fenton-type additives gave much more promising results compared to Cu-based Fenton-like additives for Hg(0) oxidation. The pH value of the sorbent solution also had a significant effect on the oxidation of Hg(0) and a suitable pH window was found to lie between 1.0 and 3.0 for this application. This may be attributed to the chain reaction mechanisms of Fe³⁺/H₂O₂ for Fenton reactions, i.e., the decomposition of H₂O₂ for the production of OOH radicals in the Fe³⁺/H₂O₂ system which is kinetically favoured under a wide range of conditions at pH values of 3 or less. At higher pH values, H₂O₂ is converted to H₂O instead of OOH radicals in the presence of Fe³⁺.     

Surfactant modification of lipases for lipid interesterification and hydrolysis reactions

Commercial grade lipases from Rhizopus japonicus, R. delemar, and Rhizomucor miehei were modified by surfactant (sorbitan monostearate), and their protein recovery and interesterification, and hydrolysis activities were investigated. By repeating the lipase modification processes three times, total protein recoveries of 17–35% could be obtained. The original lipases had no interesterification activities at all; however, all modified lipases in the first process had significant interesterification activities. In the hydrolysis reactions, all modified lipases obtained from the first process showed about three times higher specific activities than the original lipases. The modified lipases obtained from the second and third processes had lower specific interesterification and hydrolysis activities than the lipases from the first one. These results suggest that the surfactant modification process is effective not only for interesterification but also lipase purification.     

Photo-assisted Fenton reactions and growth evolution of crack-urchined CuBi2O4 microspheres assembled by nanorods

Hierarchical CuBi₂O₄ microspheres assembled by nanorods were prepared via a facile hydrothermal process. The nanorods were orderly grown along [001] crystal direction with rectangular cross-sections and a broad diameter distribution ranging of 100–350 nm. One narrow crack is distinct on the surfaces of each microsphere, which separates the microsphere into two approximately equal parts. Growth evolutions of as-prepared CuBi₂O₄ were fully discussed according to various reaction times. The microspheres were formed by radiated extension of nanorods which split along cleavage planes due to high internal stresses. The as-prepared CuBi₂O₄ exhibited a strong optical absorption in wavelength of 300–630 nm. Under visible light (λ ≥ 420 nm), an improved degradation efficiency of 89.6% to Rhodamine B (RhB) was determined with the aid of H₂O₂. The crack-urchined structures as well as the redox reactions between CuBi₂O₄ and H₂O₂ should be responsible for it.     

Effect of Fenton and photo-Fenton reactions on the degradation and biodegradability of 2 and 4-nitrophenols in water treatment

Photo-Fenton, Fenton and biodegradation reactions have been investigated in detail during the degradation of 2 and 4-nitrophenols. Fenton-type reactions accelerated nitrophenols degradation in comparison with direct photolysis using pyrex flasks (λ > 290 nm). The influence of Fe³⁺, H₂O₂, light, temperature, reactant concentration and gas atmosphere was systematically studied. Experimental techniques used involved total organic carbon determination (TOC), high pressure liquid chromatography (HPLC), nuclear magnetic resonance (NMR) and spectroscopy (OD). A solution containing 3.6·10⁻¹ M of 2-nitrophenol was degraded in ca. 3 h (30°C) in the dark and in ca. 1 h (30°C) under light where continuous photoproduction of the Fenton reagent is achieved. This study shows that the hydrolxylation of the phenol ring is fast as compared to the slower concomitant decrease in DOC in dark or light processes. Using NMR an explanation is proposed in terms of pathways involving direct oxidation of the nitrophenols under study by hydroxy type radicals. Chemical insight is provided why the photo-Fenton degradation observed for 2-nitrophenol proceeds at about half the rate than his homologue 4-nitrophenol. Biodegradability of 2-nitrophenol was monitored before and after photo-Fenton treatment by biochemical oxygen demand (BOD) and dissolved organic carbon (DOC) and indicated the formation of substances which are non-biodegradable during photo-Fenton pretreatment.     

The chemistry of lipid peroxidation metabolites: Crosslinking reactions of malondialdehyde

Malondialdehyde reacts readily with amino acids to form adducts containing vinylogous amidine linkages. Crosslinking reactions between nucleic acid bases, and amino acids induced by malondialdehyde also have been investigated. The physical data obtained for the adducts provide structural information on the possible mode of crosslinking of proteins and nucleic acids induced by this lipid metabolite.     

Water delignification by advanced oxidation processes: Homogeneous and heterogeneous Fenton and H2O2 photo-assisted reactions

The oxidation of lignin in synthetic aqueous solutions as well as in the biologically treated pulp-and-paper mill wastewater with hydrogen peroxide was studied in various methods: hydrogen peroxide UV-photolysis, homogeneous, heterogeneous and UV-assisted heterogeneous Fenton reactions, catalysed by FeZSM-5 zeolite. Contrasting the low-molecular organic contaminants, the oxidation of lignin in aqueous solutions was drastically slowed down in presence of heterogeneous FeZSM-5 zeolite, showing the superior performance of acidic homogeneous Fenton and hydrogen peroxide photolysis. This is explained by steric hindrance in oxidation of lignin with OH radicals on the catalyst surface and possible deactivation of lignin molecules adsorbed on the zeolite. The hydrogen peroxide photolysis among the studied delignification methods appeared to be the most efficient one in a wide range of pH.     

Atrazine Removal in Municipal Secondary Effluents by Fenton and Photo‐Fenton Treatments

Alternative water sources, including effluents from municipal wastewater treatment plants (MWTP) are necessary to meet increasing water demand. Advanced oxidation processes based on the Fenton reaction were applied to remove atrazine from the secondary effluents of a MWTP that uses activated sludge. Fenton, UV‐A photo‐Fenton, and UV‐C photo‐Fenton treatments were tested. Atrazine removal percentages were around 20 % for Fenton, 60 % for UV‐A photo‐Fenton and 70 % for UV‐C photo‐Fenton treatments, respectively. Organic matter mineralization by Fenton treatment was monitored and no significant reduction was observed. However, organic matter oxidation in terms of COD reduction of around 30 and 40 % were achieved by Fenton and photo‐Fenton processes, respectively. The photo‐Fenton process with UV‐C is a useful technique for atrazine degradation, leading to higher degradation than with UV‐A while also being more attractive in an economic point of view.     

In situ Raman spectroscopy studies of bulk and surface metal oxide phases during oxidation reactions

Bulk V-P-O and model supported vanadia catalysts were investigated with in situ Raman spectroscopy during n-butane oxidation to maleic anhydride in order to determine the fundamental molecular structure-reactivity/selectivity insights that can be obtained from such experiments. The in situ Raman studies of the bulk V-P-O catalysts provided information about the bulk crystalline phases, the hemihydrate precursor and its transformation to vanadyl pyrophosphate. However, the Raman experiments could not provide any molecular structural information about the amorphous and surface phases also present in this bulk metal oxide catalyst because of the strong Raman scattering from the crystalline phases. In contrast, in situ Raman studies of the model supported vanadia catalysts, where the active phase is present as a two-dimensional surface metal oxide overlayer, provided new insights into this important hydrocarbon oxidation reaction. In addition, the surface properties of the supported vanadia catalysts could be molecularly engineered to probe the role of various functionalities upon the structure-reactivity/selectivity relationship of n-butane oxidation to maleic anhydride. These fundamental studies revealed that the oxidation of n-butane required only one surface vanadia site and that the critical rate determining step involved the bridging V---O---P or V---O-support bonds. The selective oxidation of n-butane to maleic anhydride could occur over one surface vanadia site as well as multiple adjacent surface vanadia sites, but the reaction is more efficient with multiple sites. The n-butane oxidation TOF increased with the introduction of both surface Brönsted and Lewis acid sites, but only the surface Lewis acid sites increased the maleic anhydride selectivity.     

Solubilization of carotenoids from carrot juice and spinach in lipid phases: I. Modeling the gastric lumen

Our understanding of the factors determining the bioavailability of carotenoids from fruits and vegetables is poor. The apolar nature of carotenoids precludes their simple diffusion from the food structure to the absorption site at the enterocyte. Therefore, there is interest in the potential pathways for solubilization in the gut before absorption. We have studied the transfer of carotenoids from carrot juice and homogenized spinach into lipid phases that mimic the intestinal lumen at the start of digestion. In this paper we report on their transfer into olive oil under conditions pertaining to the gastric environment. A comparison between preparations of raw spinach and of carrot, in which the intact cells have been largely broken, suggests that the membrane-bound carotenoids of spinach are more resistant to transfer than the crystalline carotenoids of carrot. Lowering the pH and pepsin treatment enhance the transfer from raw vegetables. The process of blanching and freezing spinach destroys the chloroplast ultrastructure and leads to (i) a substantial increase in transfer of the carotenoids to oil and (ii) an attenuation or reversal of the enhancement of transfer seen with reduced pH or with pepsin treatment. Similar effects are seen after blanching carrot juice. Our results show that removal of soluble protein and denaturation of membrane proteins enhances the partition of carotenoids into oil. For both vegetables there is no evidence of preference in the extent of transfer of one carotenoid over another. This suggests that partitioning into oil under gastric conditions is not the stage of digestion that could lead to differences in carotenoid bioavailability.     

Solubilization of carotenoids from carrot juice and spinach in lipid phases: II. Modeling the duodenal environment

We have been investigating the factors determining the bioavailability of carotenoids from vegetables. The previous paper [Rich, G.T., Bailey, A.L., Faulks, R.M., Parker, M.L., Wickham, M.S.J., and Fillery-Travis, A. (2003) Solubilization of Carotenoids from Carrot Juice and Spinach in Lipid Phases: I. Modeling the Gastric Lumen, Lipids 38, 933–945] modeled the gastric lumen and studied the solubilization pathway of carotenes and lutein from carrot juice and homogenized spinach to oil. Using the same vegetable preparations, we have extended our investigations to solubilization pathways potentially available in the duodenum and looked at the ease of solubilization of carotenes and lutein within simplified lipid micellar and oil phases present within the duodenum during digestion. Micellar solubility of raw spinach carotenoids was low and was enhanced by freezing, which involved a blanching step. The efficiency of solubilization of carotenoids in glycodeoxycholate micelles decreased in the order lutein_carrot>lutein_{blanched-frozen spinach}>carotene_{blanched-frozen spinach}>carotene_carrot. Frozen spinach carotenoids were less soluble in simple micelles of taurocholate than of glycodeoxycholate. The results comparing the solubility of the carotenoids in mixed micelles (bile salt with lecithin) with simple bile salt micelles are explained by the relative stability of the carotenoid in the organelle compared to that in the micelle. The latter is largely determined by the polarity of the micelle. Below their critical micelle concentration (CMC), bile salts inhibit transfer of carotenoids from tissue to a lipid oil phase. Above their CMC, the bile salts that solubilize a carotenoid can provide an additional route to the oil from the tissue for that carotenoid by virtue of the equilibrium between micellar phases and the interfacial pathway. Mixed micellar phases inhibit transfer of both carotenoids from the tissue to the oil phase, thereby minimizing this futile pathway.