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Query: UMLS:C0267964 (PAA)
 2,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The capability of a family of copolymers comprising Pluronic (PEO-PPO-PEO) surfactants covalently conjugated with poly(acrylic acid) (Pluronic-PAA) to enhance the aqueous solubility and stability of the lactone form of camptothecin (CPT) was studied. The unprotected lactone form of CPT, which possesses cytotoxic activity, is rapidly converted to the ring-opened carboxylate form under physiological conditions. Firstly, surfactant properties such as critical micellization concentration (CMC) of Pluronic-PAA copolymers were characterized. Then, the equilibrium solubility partitioning and hydrolysis of the lactone form of CPT in the presence of Pluronic-PAA in water and in human serum were analyzed. CPT solubility in polymer micellar solutions was ca. 3- to 4-fold higher than that in water at pH 5. The amount of CPT solubilized per PPO was considerably greater in the Pluronic-PAA solutions than in the parent Pluronic solution, which suggests that the drug is not only solubilized by the hydrophobic cores and also by the hydrophilic POE-PAA shells of the micelles. The equilibrium partition coefficient of the CPT lactone between Pluronic-PAA solutions and water exceeded (2-3) x 10(3). The complete solubilization of CPT and the absence of chemical interactions between CPT and Pluronic-PAA were confirmed by modulated temperature differential scanning calorimetry (MTDSC), infrared spectroscopy, and X-ray diffraction of films. The loading of CPT into the Pluronic-PAA micelles was able to prevent the hydrolysis of the lactone group of the drug for 2 h at pH 8 in water. When compared to the unprotected CPT, the kinetics of the CPT hydrolysis in human serum was about 10-fold slower in the Pluronic-PAA formulations.
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PMID:Solubilization and stabilization of camptothecin in micellar solutions of pluronic-g-poly(acrylic acid) copolymers. 1521 85

The influence of hydroxyapatite (HA) content on the setting behavior and mechanical properties of hydroxyapatite-zinc oxide-poly(acrylic acid) (HA-ZnO-PAA) composite cements were investigated as a function of HA content. The working time increased with HA content up to 45 wt % HA and then decreased whilst the setting time increased with increasing HA content. Mechanical properties were determined after storage in water at 37 degrees C for 1, 7 and 28 days. Young's moduli and compressive strength go through a maximum at approximately 30 and 45 wt % HA. Young's modulus increases with time, which is consistent with an ongoing crosslinking reaction.
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PMID:The influence of hydroxyapatite: zinc oxide ratio on the setting behavior and mechanical properties of polyalkenoate cements. 1534 37

The aim of this research was to study the influence of classic (sodium hypochlorite and chlorine dioxide) and alternative (peracetic acid [PAA]) disinfectants on the formation of mutagens in surface waters used for human consumption. For this proposal, in vivo genotoxicity tests (Comet and micronucleus assay) were performed in an experimental pilot plant set up near Lake Trasimeno (Central Italy). The effects were detected in different tissues (haemocytes for the Comet assay and gills for the micronucleus test [MN]) of Dreissena polymorpha exposed in experimental basins supplied with lake water with/without the different disinfectants. Specimen collection was performed before disinfectant input for both tests and after the start of disinfection (3 h and 20 days for the Comet assay and 10 and 20 days for micronucleus test, respectively) to assess short- and long- term exposure effects during three sampling campaigns (October 2000, February 2001, and June 2001). Seasonal differences in baseline levels of DNA migration and micronucleus frequency were observed. Raw water quality modulation on disinfection by-product formation was shown. The results of the micronucleus and Comet assays on zebra mussel cells after in situ exposure to water disinfected with the two chlorinated compounds clearly indicate DNA/by-product interaction. PAA did not induce either clastogenic/aneugenic effects or DNA damage on this bioindicator.
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PMID:Comet and micronucleus assays in zebra mussel cells for genotoxicity assessment of surface drinking water treated with three different disinfectants. 1536 24

This paper contributes to the comprehension of kinetic and equilibrium phenomena governing trace metal ion sorption on organic matter coated mineral particles. Sorption and desorption experiments were carried out with trivalent metal ions M(III) (M = Eu, Cm) and poly(acrylic acid) (PAA)-coated alumina colloids at pH 5 in 0.1 M NaClO4. Under these conditions, M(III) interaction with the solid is governed by sorbed PAA. The results were compared with spectroscopic data obtained by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Within less than 30 s, a state of local equilibrium is reached between M(III) and adsorbed poly(acrylic acid). M(II) bound to the organic-mineral surface and to dissolved PAA keeps five water molecules in its first hydration sphere. Interaction of M(III) with alumina-bound PAA appears to be strongerthan with dissolved PAA. With increasing contact time, a change of the metal ion speciation occurs at the organic-mineral surface. This change is explained quantitatively by kinetically controlled reactions, which succeed a rapid local equilibrium. The experimental findings suggest, in agreement with model calculations, that a part of the initially sorbed M(III) is slowly converted to a kinetically stabilized species, thereby losing water molecules from the first coordination sphere as indicated by TRLFS. This species might be assigned as a ternary Al2O3-M(III)-PAA complex. The second part of the initially bound M(II) appears to experience as well kinetically controlled reactions, however, without showing changes in the first coordination sphere. We assume that the kinetic stabilization is the consequence of rearrangement processes of the PAA at the alumina surface.
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PMID:Interaction of Eu(III)/Cm(III) with alumina-bound poly(acrylic acid): sorption, desorption, and spectroscopic studies. 1538 58

An amphiphilic heteroarm star polymer containing 12 alternating hydrophobic/hydrophilic arms of polystyrene (PS) and poly(acrylic acid) (PAA) connected to a well-defined rigid aromatic core was studied at the air-water and the air-solid interfaces. At the air-water interface, the molecules spontaneously form pancakelike micellar aggregates which measure up to several microns in diameter and 5 nm in thickness. Upon reduction of the surface area per molecule to 7 nm2, the two-dimensional micelles merged into a dense monolayer. We suggest that confined phase separation of dissimilar polymer arms occurred upon their segregation on the opposite sides of the rigid disklike aromatic core, forcing the rigid cores to adopt a face-on orientation with respect to the interface. Upon transfer onto solid supports the PS chains face the air-film interface making it completely hydrophobic, and the PAA chains were found to collapse and form a thin flattened underlayer. This study points toward new strategies to create large 2D microstructures with facial amphiphilicity and suggests a profound influence of star molecular architecture on the self-assembly of amphiphiles at the air-water interface.
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PMID:Interfacial micellar structures from novel amphiphilic star polymers. 1546 85

A novel solid-state polymer electrolyte was constructed using layer-by-layer (LbL) polyelectrolyte assembly of linear poly(ethylenimine) (LPEI) and poly(acrylic acid) (PAA), combined with a plasticization step using oligoethylene glycol dicarboxylic acid (OEGDA). This composite film exhibits a relatively high ionic conductivity of 9.5 x 10(-5) S/cm at 25 degrees C and 22% relative humidity. Detailed characterization of the composite was undertaken using grazing-angle Fourier transform infrared (GA-FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and impedance spectroscopy. After immersing the LPEI/PAA films into OEGDA aqueous solutions, the films exhibited a swelling behavior and increased surface roughness indicative of porosity induced by reorganization of ionic interactions between LPEI and PAA in acidic solution. This internal porous structure allows inclusion of OEGDA within the multilayer and increased ionic conductivity under ambient conditions due to the combined effects of plasticization of the LbL matrix by atmospheric water as well as the added mobility of ions in molten OEGDA within the composite.
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PMID:Novel solid-state polymer electrolyte consisting of a porous layer-by-layer polyelectrolyte thin film and oligoethylene glycol. 1549 Dec 16

Samples (10 by 20 by 2.5 cm) of beef carcass tissue were inoculated (10(4) to 10(5) CFU/cm2) with Escherichia coli O157: H7 that was either non-acid habituated (prepared by incubating at 15 degrees C for 48 h in inoculated filter-sterilized composite [1:1] of hot and cold water meat decontamination runoff fluids, pH 6.05) or acid habituated (prepared in inoculated water fluids mixed with filter-sterilized 2% lactic acid [LA] runoff fluids in a proportion of 1/99 [vol/vol], pH 4.12). The inoculated surfaces were exposed to conditions simulating carcass chilling (- 3 degrees C for 10 h followed by 38 h at 1 degree C). Treatments applied to samples (between 0 and 10 h) during chilling included the following: (i) no spraying (NT) or spraying (for 30 s every 30 min) with (ii) water, (iii) cetylpyridinium chloride (CPC; 0.1 or 0.5%), (iv) ammonium hydroxide (AH; 0.05%), (v) lactic acid (LA; 2%), (vi) acidified sodium chlorite (ASC; 0.12%), (vii) peroxyacetic acid (PAA; 0.02%), (viii) sodium hydroxide (SH; 0.01%), or (ix) sodium hypochlorite (SC; 0.005%) solutions of 4 degrees C. Samples were taken at 0, 10, 24, 36, and 48 h of the chilling process to determine changes in E. coli O157:H7 populations. Phase 1 tested water, SH, PAA, LA, and 0.5% CPC on meat inoculated with non-acid-habituated pathogen populations, whereas phase 2 tested water, SC, AH, ASC, LA, and 0.1% CPC on meat inoculated with acid- and non-acid-habituated populations. Reductions in non-acid-habituated E. coli O157:H7 populations from phase 1 increased in the order NT = water = SH < PAA < LA < CPC. Reductions from phase 2 for acid-habituated cells increased in the order NT = water = SC < ASC = LA = AH < CPC, whereas on non-acid-habituated cells the order observed was NT = water = SC < AH = ASC < LA < CPC. Previous acid habituation of E. coli O157:H7 inocula rendered the cells more resistant to the effects of spray chilling, especially with acid; however, the trend of reduction remained spray chilling with water = non-spray chilling < spray chilling with chemical solutions.
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PMID:Effect of simulated spray chilling with chemical solutions on acid-habituated and non-acid-habituated Escherichia coli O157:H7 cells attached to beef carcass tissue. 1550 17

Mucoadhesive microspheres were prepared to increase gastric residence time using an interpolymer complexation of poly(acrylic acid) (PAA) with poly(vinyl pyrrolidone) (PVP) and a solvent diffusion method. The complexation between poly(acrylic acid) and poly(vinyl pyrrolidone) as a result of hydrogen bonding was confirmed by the shift in the carbonyl absorption bands of poly(acrylic acid) using FT-IR. A mixture of ethanol/water was used as the internal phase, corn oil was used as the external phase of emulsion, and span 80 was used as the surfactant. Spherical microspheres were prepared and the inside of the microspheres was completely filled. The optimum solvent ratio of the internal phase (ethanol/water) was 8/2 and 7/3, and the particle size increased as the content of water was increased. The mean particle size increased with the increase in polymer concentration. The adhesive force of microspheres was equivalent to that of Carbopol. The release rate of acetaminophen from the complex microspheres was slower than the PVP microspheres at pH 2.0 and 6.8.
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PMID:Mucoadhesive microspheres prepared by interpolymer complexation and solvent diffusion method. 1562 Aug 70

We investigate by small-angle scattering the structural behavior in water of a family of asymmetric poly(styrene-stat-(acrylic acid))-block-poly(acrylic acid), i.e., P(S-stat-AA)-b-PAA, diblock copolymers. These diblocks are of constant block ratio and increasing molar fraction, phi(AA), ranging from 0 to 1, of acrylic acid in the first P(S-stat-AA) statistical block. We identify three types of structural behavior in water: (i) for phi(AA) </= 0.25, the structures found in water are out-of-equilibrium micelle-like objects, reminiscent of the macrophase separation in the solid state, with no reorganization upon dispersion; (ii) for phi(AA) >/= 0.50, the diblocks dispersions in water are at equilibrium. For high phi(AA), the diblocks are soluble in water, demonstrating that a transition from colloid-like objects to soluble macromolecules is achieved. Close to the transition, (phi(AA) approximately 0.50), the diblocks form objects interpreted as comprising a water-swollen core formed by the P(S-stat-AA) block, surrounded by a swollen brush composed of the majority PAA block, above a apparent critical micelle concentration. However, these diblocks do not behave as macrosurfactants, and their self-association behavior is rather interpreted as a microphase separation which can arise from the incompatibility between two polymer blocks P(S-stat-AA) and PAA placed in a common solvent water.
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PMID:Chemically tuned amphiphilic diblock copolymers dispersed in water: from colloids to soluble macromolecules. 1572 64

Densely grafted polyacrylic acids (d-PAAs) with overcrowded PAA side chains on the polyacrylate main chains were synthesized and characterized. Acryloyl poly(tert-butyl acrylate) macromonomer [M-P(tert-BA)] was prepared with a definite chain length (n=29) by atom-transfer radical polymerization (ATRP), then homopolymerization was carried out to produce densely grafted P(tert-BA)s with polyacrylate main chains of two different lengths (m=27 and 161). The two d-PAAs were obtained by hydrolyzing d-P(tert-BA)s in the presence of trifluoroacetic acid (TFA). The d-PAAs exhibit intermolecular and intramolecular hydrogen bonding between the carboxylic groups of PAA side chains in dioxane and pyridine; both were investigated using proton nuclear magnetic resonance (1H NMR) spectroscopy. The intermolecular hydrogen bonding was found to be dependent on polymer concentration, temperature, and water content. The intramolecular association between the PAA side chains was found to produce a contraction of the hydrodynamic volume of the d-PAA. Intermolecular hydrogen bonding produces aggregates, as demonstrated by dynamic light scattering (DLS). The clusters were found to shrink as the overall water concentration decreased, and this effect is tentatively explained by considering the gradient in chemical potential of water inside the clusters in comparison with the solvent phase.
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PMID:Interactions between brushlike polyacrylic acid side chains on a polyacrylate backbone in dioxane-water. 1575 57


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