iAs Content Research Articles

Oxaprozin/poly(2-hydroxyethyl acrylate/itaconic acid) hydrogels: morphological, thermal, swelling, drug release and antibacterial properties

In this study, a series of novel stimuli-sensitive hydrogels based on 2-hydroxyethyl acrylate and itaconic acid monomers were designed for the controlled release of hydrophobic drug, Oxaprozin. All samples were synthesized by the free-radical crosslinking copolymerization and characterized for structural, morphological, thermal, surface charge, swelling and antibacterial properties. In order to investigate the influence of the drug on hydrogel properties the same characterization was conducted for all Oxaprozin-loaded samples. The chemical composition of hydrogels was studied using Fourier transform infrared spectroscopy, while their morphology and thermal properties were examined by scanning electron microscopy and differential scanning calorimetry. Swelling studies, conducted in the physiological pH range from 2.20 to 8.00 and in the temperature range from 25 to 50 °C, showed that the loaded drug does not modify the pH and temperature sensitivity of the hydrogels, but reduces their swelling capacity. The in vitro drug release study conducted at pH 2.20 and 7.40 showed that all hydrogels can be tailored as colon specific drug delivery systems, and the drug release rate can be effectively controlled by IA content. In addition, the antibacterial activity of the hydrogels was determined against Escherichia coli and Staphylococcus aureus, by the zone of inhibition test. Results of our study indicate that these “smart” hydrogels, with specific morphology, surface charge, swelling capacity, drug loading efficiency and release behavior, could be designed to obtain an enhanced and site-specific controlled drug release system by simply adjusting their composition.

Total and inorganic arsenic in foods of the first Hong Kong total diet study

Arsenic (As) is a metalloid that occurs in different inorganic and organic forms, which are found in the environment from both natural occurrence and anthropogenic activity. The inorganic forms of As (iAs) are more toxic as compared with the organic As, but so far most of the occurrence data in food collected in the framework of official food control are still reported as total As without differentiating the various As species. In this paper, total As and iAs contents of 600 total diet study (TDS) samples, subdivided into 15 different food groups, were quantified by high-resolution inductively coupled plasma mass spectrometry (HR-ICP/MS) and hydride generation (HG) ICP/MS respectively. The method detection limits for both total As and iAs were 3 μg As kg−1. As the samples were prepared for TDS, food items were purchased directly from the market or prepared as for normal consumption, i.e. table ready, in the manner most representative of and consistent with cultural habits in Hong Kong as far as practicable. The highest total As and iAs content were found in ‘fish, seafood and their products’ and ‘vegetables and their products’ respectively. Besides, this paper also presents the ratios of iAs and total As content in different ready-to-eat food items. The highest ratio of iAs to total As was found in ‘vegetables and their products’. It is likely that iAs in vegetables maintained its status even after cooking.

Antimicrobial hydrogels based on 2-hydroxyethyl methacrylate and itaconic acid containing silver(I) ion

The objective of our study was to develop new antimicrobial hydrogels silver/poly(2-hydroxyethyl methacrylate/ itaconic acid) (Ag/P(HEMA/IA)). The P(HEMA/IA) samples, with different HEMA/IA ratio, were prepared by free radical crosslinking copolymerization. Ag ion were introduced in hydrogels by immersing dried P(HEMA/IA) disks in silver(I) salt solution, which was confirmed by FTIR spectroscopy. The in vitro controlled release of silver(I) ion from (Ag/P(HEMA/IA)) gels, and antimicrobial activity during the release period were also studied. The release profiles have shown a two-phase exponential profile, with fast initial phase, followed by a much slower release rate. Kinetic parameters determined, have indicated Fickian transport of Ag(I) ion in the initial phase. It is perceived that the antimicrobial activity of the Ag/P(HEMA/IA) depends on IA content. Excellent antimicrobial potential was maintained during the entire release time.

Electrospun Nanofibers of Acrylonitrile and Itaconic Acid Copolymers and their Stabilization

(APS) as an oxidant in the aqueous medium,and nanofibers produced by electrospinning . Electrospun nanofiber mats were by treated heat under air atmosphere to be stabilized. Nanofiber production from AN-IA copolymers and suitability of the nanofiber as carbon nanofiber precursor is discussed. Copolymer are characterized using Fourier Transform Infrared - Attenuated Total Reflectance spectrometer (FTIR-ATR), Nuclear Magnetic Resonance Spectroscopy (1H-NMR), differential scanning calorimeter (DSC), thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The effect of IA content on the spectroscopic and thermal properties of AN-IA copolymers was investigated. Increasing IA content confirmed by spectroscopic methods seriously affects thermal properties which is important for carbon nanofiber production. IA provides a catalytic effect on stabilization process by decreasing initiation cyclization reaction temperature from 202 to 195 oC. Elecrospinning from the AN-IA copolymer solutions in dimethyl foramide (DMF) was performed, morphology of nanofibers was monitored using Scanning Electron Microscopy (SEM). Bead free nanofibers were produced from AN-IA copolymer solutions under same conditions. Average nanofiber diameter decreases from 878±18 to 376±7 nm according to increasing IA content in copolymers. The nanofiber mats produced were treated at high temperature under air atmosphere for oxidative stabilization. Stabilized nanofibers were characterized using FTIR-ATR spectrometer and a new structure was monitored as a result of cyclization reactions. The stabilized nanofibers were also characterized mophologically using SEM. Volume loss occurring after heat treatment calculated based on the nanofiber diameter changes. Consequently, electrospun nanofibers can be suggested as a carbon nanofiber precursor due to suitability for electrospinning and stabilization process.

Total and Inorganic Arsenic in Marketed Food and Associated Health Risks for the Catalan (Spain) Population

Inorganic arsenic (iAs) is considered to be a human carcinogen. In this paper, total (As) and iAs contents of 215 food products and drinks (i.e., seafood, fruits and vegetables, meat products, oils and fats, rice and rice products, seasonings, and alcoholic drinks) marketed in Catalonia (Spain) were quantified by inductively coupled plasma-mass spectrometry. The analytical method described was used for different food products, obtaining feasible results without the need to couple LC-ICP-MS for iAs. Daily As and iAs intakes for the average adult Catalan consumer were estimated at 354 and 6.1 μg/day/person, respectively, using consumption data from the Catalan Nutrition Survey (ENCAT). The highest As content was found in seafood, contributing 96% of dietary As intake, whereas rice presented the highest iAs values, corresponding to 67% of dietary iAs intake. As cooking process may affect iAs content, boiled rice was evaluated, showing an iAs reduction (up to 86%) when using higher water volumes (30:1 water/rice ratio) than those used in previous studies. This iAs exposure was slightly below the exposure risk range stated by the European Food Safety Authority (0.3-8 μg/kg of body weight/day), although the possibility of a risk to the population with high rice consumption cannot be excluded.

Determination of Arsenic Species in Polished Rice Using a Methanol-water Digestion Method

Inorganic arsenic (iAs) in food is much more toxic than organic. Four arsenic species, arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA), and dimethylarsenic acid (DMA) in polished rice cultivated at the mining areas of Korea were evaluated. A methanol-water (1:1) mixture was used for extraction of As compounds and an anion Hamilton PRP X-100 column for As species separation in HPLC-ICP-MS. The limits of detection were 5.3, 3.7, 19.2, and 3.7 ώg/kg on dry weight basis for AsIII, AsV, MMA, and DMA, respectively. When this method was applied to eleven polished rice samples, the mean value of iAs content in total As was approximately 57%.

Ingestion and excretion of arsenic compounds present in edible brown algae, Hijikia fusiforme, by mice

The element arsenic is a carcinogen and toxic for humans and other living organisms. Some seaweeds contain high amounts of inorganic arsenic (iAs). In particular, Hijikia fusiforme has a high iAs content of approximately 50%. In this study, we examined the absorption, metabolism, excretion, and accumulation of arsenic compounds in mice after the administration of Hijiki. The single-dose experiment, wherein a single dose of cooked Hijiki was administered to the mice, revealed that the urinary and fecal excretion of arsenic compounds was the highest on the first day of dosing, and it became clear that 66–92% of arsenic was excreted within 3 days after administration of the first dose. The repeated-dose experiment, wherein repeated doses of cooked or dried Hijiki were adminstered to the mice, arsenic was detected in all the tissues, but only approximately 5% of the administered dose of arsenic was detected as residual arsenic. These results suggest that the arsenic present in cooked Hijiki is accumulated in very small amounts in mice.

Evaluation of a Nitric Acid-based Partial-digestion Method for Selective Determination of Inorganic Arsenic in Rice

Arsenic (As) uptake in human occurs via the food chain mainly. The Joint FAO/WHO Expert Committee on Food Additives has established the provisional tolerable weekly intake level for As as an inorganic As (iAs) value, because iAs in food is much more toxic than organic As. In this study, we studied an acid based partial-digestion method for the complete extraction of arsenicals from rice. HPLC/ICP-MS was used to determine the concentration of iAs selectively. The conditions adopted to extract arsenicals from a 0.5 g of finely ground rice sample were addition of 2 mL of 0.15 mol/L nitric acid and heating at 80 degrees C for 2 hr. The LOD and LOQ for iAs were 0.0024 and 0.0079 mg/kg dry weight, respectively. Recovery studies showed good accuracy. When the method was applied to ten short-grain brown rice samples, the iAs concentrations were 0.108-0.227 mg/kg dry weight and the total As concentrations were 0.118-0.260 mg/kg dry weight. Although dimethylarsinic acid was also detected in most samples, the percentage of iAs content in total As content was 62.2-96.3%. Thus, iAs was the principal As species in the short-grain brown rice samples tested.

Investigation of thermal behavior of poly(2‐hydroxyethyl methacrylate‐co‐itaconic acid) networks

AbstractThe thermal behavior of poly(2‐hydroxyethyl methacrylate) [PHEMA] homopolymer and poly(2‐hydroxyethyl methacrylate‐co‐itaconic acid) [P(HEMA/IA)] copolymeric networks synthesized using a radiation‐induced polymerization technique was investigated by differential scanning calorimetry, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The glass‐transition temperature (Tg) of the PHEMA homopolymer was found to be 87°C. On the other hand, the Tg of the P(HEMA/IA) networks increased from 88°C to 117°C with an increasing amount of IA in the network system. The thermal degradation reaction mechanism of the P(HEMA/IA) networks was determined to be different from the PHEMA homopolymer, as confirmed by thermogravimetric analysis. It was observed that the initial thermal degradation temperature of these copolymeric networks increased from 271°C to 300°C with IA content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1602–1607, 2007

The effect of solvent composition on swelling and shrinking properties of poly(acrylamide-co-itaconic acid) hydrogels

The peculiarities of the equilibrium swelling ratio and swelling–shrinking kinetics of polyelectrolyte copolymeric hydrogels consisting of acrylamide and itaconic acid (AAm/IA) have been studied in water/nonsolvent (acetone, methanol, ethanol and 1-butanol) mixtures as a function of solvent composition and IA content in the hydrogel. The phase transition of these hydrogels was generated by changing the solvent composition by progressive substitution of water by the nonsolvent. For all P(AAm/IA) hydrogels, the form of the shrinking curves was determined to be strongly dependent on the type of the nonsolvent used. The rate of shrinking of these hydrogels increased in the order 1-butanol < ethanol < methanol < acetone.

Effects of Temperature and Surfactants on the Equilibrium Swelling Behavior of Poly[acrylamide‐co‐(itaconic acid)] Hydrogels

AbstractSummary: The swelling equilibrium of poly(acrylamide) [PAAm] and poly[acrylamide‐co‐(itaconic acid)] [P(AAm/IA)] hydrogels was studied as a function of temperature and IA content in aqueous solutions of surfactants: sodium dodecyl sulfate (SDS, anionic) and hexadecyltrimethylammonium bromide (HTAB, cationic). P(AAm/IA) hydrogels in water exhibited reentrant conformational transitions depending on temperature, whereas PAAm hydrogels were not affected with the change of temperature. The equilibrium‐volume‐swelling ratio of P(AAm/IA) hydrogels increased sharply in SDS solutions, with an increase of the mole percent of IA. However, in HTAB solution, the equilibrium‐volume‐swelling ratio of these hydrogels decreased with an increase of IA content.The equilibrium volume‐swelling ratios of the hydrogels in water shown as a function of temperature.magnified imageThe equilibrium volume‐swelling ratios of the hydrogels in water shown as a function of temperature.

Semi-interpenetrating polymer networks based on polyacrylamide and poly[itaconic acid

The effect of pH and temperature on the equilibrium swelling properties of PIA/PAAm semi-IPNs were investigated.Semi-IPNs based on polyacrylamide (PAAm) and poly(itaconic acid) (PIA) were prepared by two different techniques, by polymerizing itaconic acid in the presence of polyacrylamide gel (Semi-IPNs-l) and by making the polyacrylamide gel in the presence of previously synthesized poly(itaconic acid) (Semi-IPNs-ll), with different PIA/PAAm mass ratios. The equilibrium swelling degree of an ionic network depends very much on the concentration of ionisable groups. The addition of a small amount of itaconic acid dramatically changes the swelling behavior of PAAm. Increase of the ionic monomer (IA) produces swelling degrees that increase to a high extent when the pH of the buffer solution is higher than the nominal pKa values of the acid groups. Gels with higher IA content swell less than PAAm gels in low pH buffers. At low pH, when complexation due to hydrogen bonding occurs between the carboxylic groups and amide groups of acrylamide, the polymer network collapses and the swelling ratio is low. The presence of hydrogen bonds in the complexes causes additional constraints in the network, acting as a physical crosslinking and makes the network less hydrophilic, because the carboxylic groups on the PIA are occupied in the complexes. As opposed to this, the equilibrium swelling degrees change very little with pH of the solution in nonionic PAAm gel.Hydrogels exhibit continuous changes in water content as a function of temperature. The swelling degree increases with increasing temperature due to gel expansion upon warming.

Dynamic deswelling studies of poly( N-vinyl-2-pyrrolidone/itaconic acid) hydrogels swollen in water and terbinafine hydrochloride solutions

Deswelling kinetics of water and terbinafine hydrochloride adsorbed poly( N-vinyl-2-pyrrolidone/itaconic acid) P(VP/IA) hydrogels were investigated. Hydrogels were prepared by irradiating the ternary mixture of VP/IA and cross-linking agent ethylene glycol dimethacrylate (EGDMA) in water by γ-rays at ambient temperature. Hydrogels swelled in pure water and terbinafine hydrochloride (TER-HCl) solutions at room temperature and deswelling or water loss were investigated between 4 and 45 °C temperature range and on human skin. The influence of IA content, % swelling, temperature and TER-HCl content on the water loss from gel matrix were investigated. Induction time for 80% water loss from hydrogel systems are found to increase from 9.6 to 21.2 h by increasing IA content in the gel system at 25 °C and decreased by 11 h with addition of TER-HCl in the gel system. Kinetic analyses had shown that the basic properties affecting the water loss behavior of these hydrogels are the IA and TER-HCl content and temperature of the medium.

Dynamic oscillatory shear properties of potentially melt processable high acrylonitrile terpolymers

Polyacrylonitrile (PAN) terpolymers consisting of acrylonitrile/methyl acrylate (AN/MA) systems with added amounts of a termonomer (acid based) were synthesized in an effort to generate melt spinnable carbon fiber precursors. The complex viscosity was measured as a function of time in the temperature range of 200–220 °C, and was found to be dependent on both, the amount, as well as the nature of the termonomer. For the different acid termonomers studied, the cyclization/crosslinking reactions occurring during stabilization as evidenced by the increase in viscosity over time of the PAN system ranged in the order, itaconic acid>acrylamide>methyl acrylic acid>acrylic acid (IA>AM>MAA>AA). Dynamic shear experiments indicated that an AN/MA system containing 3 mol% IA seemed well suited for melt spinning and stabilization. A chemorheological correlation was used to describe the viscosity variation in the PAN system as a function of IA content, temperature and time.

Controlled release of antifungal drug terbinafine hydrochloride from poly( N-vinyl 2-pyrrolidone/itaconic acid) hydrogels

Adsorption and controlled release of terbinafine hydrochloride (TER-HCl) to and from pH-sensitive poly( N-vinyl 2-pyrrolidone/itaconic acid) P(VP/IA) hydrogels were investigated. P(VP/IA) hydrogels were prepared by irradiating the ternary monomer mixtures of N-vinyl 2-pyrrolidone/itaconic acid/ethylene glycol dimethacrylate in aqueous solution by γ-rays at ambient temperature. Hydrogels containing antifungal drug TER-HCl, at different drug-to-polymer ratios, were prepared by direct adsorption method. The influence of IA content in the gel on the adsorption capacities of hydrogels and the effect of pH on the releasing behavior of TER-HCl from the gel matrix were investigated. Terbinafine adsorption capacity of hydrogels was found to increase from 6 to 82 mg of TER-HCl per gram of dry gel with increasing drug concentration and amount of IA in the gel system. In-vitro drug-release studies in different buffer solutions showed that the basic parameters affecting the drug-release behavior of hydrogels are the pH of the solution and the IA content of the hydrogel.

Reactive compatibilization of nylon 6/styrene–acrylonitrile copolymer blends: Part 3. Tensile stress–strain behavior

The stress–strain behavior of blends of nylon 6 (PA) and a styrene–acrylonitrile copolymer (SAN) compatibilized by an imidized acrylic polymer (IA) was evaluated in terms of the IA content and the dispersed SAN25 particle size. PA/SAN blends can be considered as a simpler version of industrially important PA/ABS blends; therefore, this study provides better understanding of the stress–strain behavior of compatibilized PA/ABS blends. The IA content was varied from 0 to 5 wt%; whereas the ratio of PA to SAN25 was held at 7/3; and in all cases the polyamide formed the continuous phase. From experiments using a Brabender batch mixer or an extruder as the mixing device, a reduction of dispersed particle size was observed with the addition of as little as 0.1 wt% IA. It was revealed from the experiments using a Brabender batch mixer that more than 0.5 wt% IA was necessary to prevent domain coalescence. The blends containing 1 wt% or more IA show necking and considerable plastic deformation. Transmission electron microscopy revealed that the normally brittle SAN25 particles were transformed into elongated shapes and undergo shear yielding under certain circumstances as the specimens experienced plastic deformation during stress–strain testing. Although the macroscopic elongation at break and the particle distortion ratio, which is defined as the ratio of the major axis to the minor axis of the elongated particles, are somewhat correlated, the local deformation in the neck region is much larger than the elongation at break. Thus, the ultimate capability for plastic deformation of the IA compatibilized blends is much larger than the overall elongation at break. The distortion ratio of the particles was observed to be as high as 6–7. There seems to be a relationship between the SAN25 particle size and the extent of plastic deformation realized. These experiments, however, do not differentiate the effect of diminishing particle size from increasing adhesion between the phases. Thus, it is not possible to assign unambiguously the dominant factor that permits the plastic deformation of the brittle SAN phase.

Thermal behaviour of acrylonitrile copolymers having methacrylic and itaconic acid comonomers

The effect of comonomers, methacrylic (MAA 3–6mol%) and itaconic acid (IA 2–3mol%) on the glass transition temperature, Tg, hydration melting and thermo-oxidative stabilization of acrylonitrile copolymers has been studied by differential scanning calorimetry (DSC). While, two Tg‘s were observed, near 70 and 140°C, for PAN homopolymer, copolymers showed another baseline shift below 70°C. The melting point, Tm, of PAN and copolymer, P(AN/IA) containing 3.2mol% of IA, has been reduced to 186 and 158°C, respectively, in high-pressure DSC. The copolymers showed two distinct melting peaks in the first heating cycle, but the melt on subsequent cooling exhibited a single exotherm due to crystallization. The melting point of IA copolymer (158°C) was found to be lower than that of MAA copolymer (164°C) and PAN homopolymer (186°C). Tm further decreases with increase in the comonomer content. In the second heating cycle, observed Tm is higher than that noted in the first heating run, indicating some amount of physical transformations. The enthalpy of fusion, ΔHf decreases with the incorporation of comonomers, e.g. it is maximum for PAN homopolymer (57.8Jg−1) and minimum for P(AN/IA) copolymer (26Jg−1) having 3.2mol% of IA content. The lower entropy of fusion (ΔSf) of copolymers indicates that they are less mobile in the molten state. DSC of copolymers run in air atmosphere, at a heating rate of 10°Cmin−1, shows a broader exotherm compared to homopolymer. But, the broadening of exotherm seems to be more in P(AN/IA) polymers than P(AN/MAA) and the onset of cyclization shifts to a lower temperature as compared to PAN. The activation energy of nitrile cyclization, Ea, for PAN is found to be 30kcalmol−1. For copolymer P(AN/IA), IA=3.2mol%, Ea is 18kcalmol−1.

The biology of airway dendritic cells.

Recent work from our laboratory has identified a network of constitutively class II MHC (Ia) bearing dendritic cells (DC) within the epithelium of the conducting airways of laboratory animal species and in humans. The density of DC within the respiratory tract is highest in those areas exposed to greater amounts of inhaled antigen and further work has identified these DC as being critically important in controlling the induction of immune responses within the airways. The DC population in the airway epithelium is renewed every 48-72 h; this represents a more rapid turnover than DC in other tissues which are exposed to a smaller antigenic load. In addition to these results we will discuss other work which shows that airway DC are a very reactive population, comparable with neutrophils in their response to acute inflammatory stimuli and that their numbers and Ia content can be modulated following exposure to topical and systemic steroids. Finally we will discuss the development of these cells after birth and how this may influence the pathogenesis of immune regulated diseases such as asthma and allergic rhinitis.

Thermal properties of polyacrylonitrile copolymers having various chemical compositions

1. The thermal oxidative degradation of PAN fibres having an IA content from 1.2 to 6.4% in the copolymer has been studied by the DTA method.