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PubMedDate not supplied

Characterization of nanostructure of stimuli-responsive polymeric composite membranes.

To elucidate the mechanism of stimuli-responsive permeability and to optimize the design, the nanostructure of polymeric composite membranes, developed in our laboratory, was characterized. The membranes were prepared to contain various amounts of stimuli-responsive nanoparticles of poly(N-isopropylacrylamide-co-methacrylic acid), with or without polyelectrolyte coating. Scanning electron microscopy and X-ray photoelectron spectroscopy were used respectively to examine the morphology and surface chemical composition, whereas atomic force microscopy and laser scanning confocal microscopy were employed to characterize the in situ surface and internal structure of the membranes in aqueous media of various pHs. The porous structure was evidenced in the presence of the nanoparticles. The surface content of the nanoparticles increased with increasing particle concentration while the polyelectrolyte coating was nearly undetectable. AFM images revealed that the particles in the membranes shrank with a concomitant increase in pore size as the buffer pH decreased. LSCM results indicated that particles were distributed through the membrane as interconnected clusters.

Acrylamides↗
PubMed1999

Effects of long-term sub-lethal concentrations of dental monomers on THP-1 human monocytes.

Studies have shown that monomers from dental resins are acutely cytotoxic, but little is known of their long-term effects at sub-lethal concentrations. The current study determined the long-term effects of sub-lethal concentrations of TEGDMA (triethyleneglycol dimethacrylate) and Bis-GMA (bisphenol-glycidylinethacrylate), two common dental monomers, on the in vitro cellular proliferation, succinic dehydrogenase activity, and total cellular protein production of monocytes. Human THP-1 monocytes were exposed to concentrations of 100, 200, and 400 micromol l(-1) of TEGDMA or 1, 5, and 25 micromol l(-1) Bis-GMA for 5 weeks. Controls received only vehicle solutions of ethanol. Each week cellular proliferation (hemocytometer), succinic dehydrogenase (SDH) activity (MTT) and total cellular protein (bicinchoninic acid) were assessed. The results were compared with ANOVA and Tukey intervals (alpha = 0.05). TEDGMA had no proliferative or cellular protein effects, but increased SDH activity 20-60% in week 1 (p < 0.05). SDH activity then decreased 40% in week 2, followed by a gradual increase of 30-40% over week 3-5 (p < 0.05). Bis-GMA reduced proliferation by 40-60% from 1-5 weeks exposure (p < 0.05). However, SDH activity and total protein per cell were not affected. There was some indication of increased SDH activity after 5 weeks (20-30%, p < 0.05). Sub-lethal concentrations of TEGDMA and Bis-GMA have significant long-term effects on monocytes at low-dose 5-week exposures in vitro. Each monomer acted differently.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2003

Coating uniformity and coating efficiency in a Bohle Lab-Coater using oval tablets.

The aim of this study was the examination of the influence of tablet size (two different sized oval tablets), batch size, pan speed and inclination of the rotation axis on the coating uniformity and efficiency in a Bohle Lab-Coater BLC 5. The coating uniformity was appraised using the mass variance, the dissolved amount of acetaminophen after 2 h in hydrochloric acid pH 1.0 at a polymer loading of 3 mg/cm(2) and the minimum amount of polymer for an enteric coating. The mass variance of the final tablets decreased with increasing pan speed. There was a linear and quadratic effect in the case of small oval tablets and a linear effect for the large tablets. The minimum amount of polymer required for gastric resistance depends on the pan speed for both tablet sizes. The dissolved amount of acetaminophen after 2 h in simulated gastric fluid was influenced linearly by the batch size for both kind of tablets. In the case of the large oval tablets it was also influenced by the pan speed, the batch size and the inclination of the rotation axis. The dissolved amount of acetaminophen increased with increasing pan speed and batch size. A relation between the coating process efficiency and the investigated influence variables could not be established.

Acetaminophen↗
PubMed2005

A comparative in vitro assessment of the drug release performance of pH-responsive polymers for ileo-colonic delivery.

The aim of this study was to investigate the in vitro dissolution characteristics of pH-responsive polymers in a variety of simulated fluids. Prednisolone tablets were fabricated and coated with the following polymer systems: Eudragit S (organic solution), Eudragit S (aqueous dispersion), Eudragit FS (aqueous dispersion) and Eudragit P4135 (organic solution). Dissolution tests were conducted using a pH change method whereby tablets were transferred from acid to buffer. Three different buffer media were investigated: two compendial phosphate buffers (pH range 6.8-7.4) and a physiological buffer solution (Hanks buffer) with very similar ionic composition to intestinal fluid (pH 7.4). There was considerable drug release from tablets coated with Eudragit P4135 in acid, prompting discontinuation of further investigations of this polymer. Eudragit S (organic solution), Eudragit S (aqueous dispersion) and Eudragit FS on the other hand prevented drug release in acid, though subsequent drug release in the buffer media was found to be influenced by the duration of tablet exposure to acid. At pH 7.4 drug release rate from the polymer coated tablets was similar in the two compendial media, however in the physiological buffer, they were found to differ in the following order: Eudragit S (aqueous dispersion)>Eudragit FS>Eudragit S (organic solution). The results indicate that the tablets coated with the newer Eudragit FS polymer would be more appropriate for drug delivery to the ileo-colonic region in comparison to the more established Eudragit S. More importantly, however, dissolution in the physiological buffer was found to be markedly slower for all the coated tablets than in the two compendial buffers, a result akin to reported slower dissolution of enteric coated tablets in vivo. There is therefore the need to adequately simulate the ionic composition of the intestinal fluid in the dissolution media.

Body Fluids↗
PubMedDate not supplied

Immobilization of whole-cell penicillin G acylase by entrapping within polymethacrylamide beads.

Escherichia coli ATCC 11105 containing the periplasmic penicillin G acylase was entrapped within a copolymer of methacrylamide and N,N'-methylenebisacrylamide. A solution of monomer that was made up from methacrylamide and N,N'-methylenebisacrylamide dissolved in buffer was mixed with lyophilized cells and ammonium persulfate. This suspension was then pumped drop by drop into in soybean oil supplemented with 0.06% (v/v) 3-(dimethylamino)-propionitril. During submerging in the oil phase, the droplets were hardened and induced to polymerize within the droplets. Particles with a volume ranging from 0.013-0.017 mL per bead containing a biomass concentration up to 38.0 g/L were prepared. The optimal condition for the deacylation of penicillin G to 6-aminopencillanic acid (6-APA) catalyzed by the immobilized whole-cell penicillin G acylase was found to be 45 degrees C and pH 8.0. Product inhibition of this enzyme by 6-APA could be eliminated by controlling pH value at 8 during the course of penicillin G hydrolysis using a pH-stat. Conversion determined by the pH-stat method were 0.3% higher than that by p-dimethylaminobenzaldehyde method. Cell concentration in the matrix was found to be an important factor influencing the maximum velocity and the specific activity retained in the matrix. A kinetic model, in which the mass transfer resistances as a result of external film mass transfer and pore diffusion were assumed to be negligible, could properly describe the hydrolysis of penicillin G by the cells entrapped within the polymethacylamide beads.

Cell Count↗
PubMed2004

The effects of water and acetone-based dentin adhesives on apical microleakage.

In this study, the aim was to assess the in vitro apical microleakage of a resin-based sealer used with two different adhesives. Thirty nine freshly extracted maxillary incisors were used. The teeth were decoronated at the cemento-enamel junction with a water-cooled fissure bur. Chemo-mechanical debridement of the root canals was accomplished with the step-back technique. The smear layer was removed by 19% ethylenediamine tetra acetic acid (EDTA). The roots were then divided into three experimental groups of thirteen teeth in each. Specimens in group 1 were filled with gutta-percha, AH Plus sealer, and water-based adhesive system (Syntac Single Component). Group 2 specimens were filled with gutta-percha, AH Plus sealer, and acetone-based dentin adhesive (Prime & Bond NT ). Specimens of group 3 were filled with only gutta-percha and AH Plus sealer (no adhesive was applied). The teeth were immersed into 2% methylene blue solution. Apical sealing qualities were assessed by measuring the linear dye penetration with a stereomicroscope. Dentin tubule penetration was observed under scanning electron microscopy (SEM). Results showed no statistically significant difference between the materials used, however, the leakage in group 2 was less than group 1 and 3.

Acetone↗
PubMed1996

Comparative and experimental pathology of fibrosing colonopathy.

Although the occurrence of fibrosing colonopathy is temporally associated with the introduction of high-strength pancreatic enzyme supplements, its pathogenesis remains uncertain. The UK case-control study showed fibrosing colonopathy to be associated with high doses of high-strength pancreatic enzyme supplements and with a group of brands which occupy only 30% of the market. Two alternative hypotheses were proposed to explain the aetiology of fibrosing colonopathy: exposure to high levels of enzymes or to as yet unidentified components of the formulation. Comparison of the anatomical pathology of fibrosing colonopathy with that of previously encountered forms of obstructive gastrointestinal pathology, such as stricturing lesions due to potassium chloride preparations and nonsteroidal anti-inflammatory drugs, confirmed it to be a previously unencountered, long-segment lesion of the colon. Thus the use of the descriptive term 'stricture' is a misnomer leading to much clinical confusion when discussing obstructive bowel pathology in cystic fibrosis patients. Gavage studies in the rat with one of the two monomers (ethyl acrylate) forming the methacrylic acid copolymer (Eudragit L30D55) used for the enteric coating of the high-strength pancreatic enzyme supplements, have shown pathology comparable to fibrosing colonopathy. These findings prompted a series of exploratory studies in adolescent pigs. After seven days caecal gavage of Eudragit L30D55 at doses of 10, 50 or 500 mg/kg/day (comparable to human intake), extensive fibrosing colonopathy-like changes, inclusive of dense submucosal fibrosis, were noted at all dose levels in seven out of nine animals. Similar studies of the monomer components of the Eudragit L30D55 copolymer, at dose levels of 0.015 to 50 mg/kg/day, representing possible residues in Eudragit L30D55, did not produce comparable changes. The conclusion is that, although the precise mechanisms have not been elucidated, the role of enteric coatings containing Eudragit L30D55 in the pathogenesis of fibrosing colonopathy requires urgent further study.

Acrylic Resins↗
PubMed2006

Zwitterionic stationary phase with covalently bonded phosphorylcholine type polymer grafts and its applicability to separation of peptides in the hydrophilic interaction liquid chromatography mode.

A novel phosphorylcholine type zwitterionic stationary phase was synthesized by graft polymerization of 2-methacryloyloxyethyl phosphorylcholine onto the surface of porous silica particles. The resulting material possesses both negatively charged phosphoric acid and positively charged quaternary ammonium groups, which renders it a low net charge over a wide pH range. The composition of the surface grafts were determined by elemental analysis and solid state NMR, and the surface charge (zeta-potential) in different buffer solutions were measured using photon correlation spectroscopy. Separation of several peptides was investigated on packed columns in the hydrophilic interaction liquid chromatography (HILIC) separation mode. It was shown that small peptides can be separated based on hydrophilic interaction and ionic interaction between the stationary phase and analyte. The organic solvent composition, the pH and the salt concentration of the eluent have strong effects on the retention time. Compared to native silica before grafting, the newly synthesized zwitterionic material gave more stable retention times for basic peptides over pH range 3-7 due to elimination of the dissociation of silanol groups.

Acetonitriles↗
PubMed1991

The effects on the dental pulp of a composite resin and two dentine bonding agents and associated bacterial microleakage.

The pulpal reaction associated with a composite resin alone and composite resin used in conjunction with two dentine bonding agents was studied. Class V cavities were prepared on the labial surfaces of the canine teeth of 18 male ferrets. After acid etching of the enamel margins, the cavities were restored with either a composite resin alone or in combination with one of two dentine bonding agents, Scotchbond and Gluma. One cavity in each animal was filled with Kalzinol as a control. The animals were killed after 7, 14 and 28 days. After histological processing, the pulpal changes were assessed qualitatively and quantitatively according to standard criteria. There were variations in the pulpal response at all time intervals. The responses to the two dentine bonding agents were similar to those found with composite resin alone. No pulpal inflammation was observed in the control teeth. Gram-positive micro-organisms were identified at the interface of restoration and cavity wall, or within the dentinal tubules in virtually all cases in which pulpal inflammation was observed.

Animals↗
PubMed2006

Gastrointestinal transit and mucoadhesive characteristics of complexation hydrogels in rats.

The aim of this study was to investigate the gastrointestinal (GI) transit and mucoadhesive properties of complexation hydrogels, poly(methacrylic acid-grafted-ethylene glycol). The fluorescent labeled complexation hydrogels containing different molar ratios of methacrylic acid/ethylene glycol and different particle diameters were synthesized by free radical solution polymerization. The GI transit profiles of microparticles after oral administration to rats were evaluated by determining the polymer remaining in the stomach and the small intestine. Moreover, the mucoadhesion to the duodenal mucosa was evaluated by an in situ perfusion method. The ethylene glycol content and particle size of the hydrogels influenced significantly the GI transit and mucoadhesive capacities. The microparticles composed of polymers prepared from 1:1 ratio of methacrylic acid/ethylene glycol and having diameters of <53 microm showed the strongest mucoadhesive capacity. These findings indicated that the hydrogels may be a promising tool for improving oral bioavailability of various drugs, which are poorly absorbed from the GI tract.

Adhesiveness↗
PubMed2002

Microleakage of new all-in-one adhesive systems on dentinal and enamel margins.

OBJECTIVE: The aim of this study was to compare the microleakage of new all-in-one adhesive systems on enamel and dentin margins with that of a conventional total-etch system. METHOD AND MATERIALS: Thirty buccal Class V cavities were prepared with enamel and dentin margins in 30 bovine teeth and randomly divided into three groups of 10 specimens each. Group 1 was bonded with Etch & Prime, group 2 with Prompt L-Pop, and group 3 with 35% phosphoric acid plus Prime & Bond 2.1. After being stored in an environment of 100% humidity for 24 hours, the teeth were immersed in a 50% silver nitrate solution for 24 hours and then put in a developing solution for 15 minutes. The specimens were sectioned vertically and buccolingually, and microleakage was evaluated on a scale of 0 to 3. RESULTS: For the enamel margin, statistical analysis revealed that there was no significant difference between groups 1 and 2 or groups 1 and 3 but that there was a statistically significant difference between groups 2 and 3. Statistical analysis revealed no significant difference among the groups in dentinal microleakage. CONCLUSION: Among the three adhesive systems used in this study, Prompt L-Pop provided the least microleakage in enamel; however, there was no statistically significant difference among the groups on dentin margins.

Acetone↗
PubMed2005

The properties of covalently immobilized trypsin on soap-free P(MMA-EA-AA) latex particles.

The covalent immobilization of trypsin onto poly[(methyl methacrylate)-co-(ethyl acrylate)-co-(acrylic acid)] latex particles, produced by a soap-free emulsion polymerization technique, was carried out using the carbodiimide method. The catalytic properties and kinetic parameters, as well as the stability of the immobilized enzyme were compared to those of the free enzyme. Results showed that the optimum temperature and pH for the immobilized trypsin in the hydrolysis of casein were 55 degrees C and 8.5, both of which were higher than that of the free form. It was found that K(m) (Michaelis constant) was 45.7 mg . ml(-1) and V(max) (maximal reaction rate) was 793.0 microg . min(-1) for immobilized trypsin, compared to a K(m) of 30.0 mg . ml(-1) and a V(max) of 5 467.5 microg . min(-1) for free trypsin. The immobilized trypsin exhibited much better thermal and chemical stabilities than its free counterpart and maintained over 63% of its initial activity after reusing ten times.

Enzymes, Immobilized↗
PubMed2000

Preparation and characterization of pH-responsive polymeric micelles for the delivery of photosensitizing anticancer drugs.

pH-responsive polymeric micelles (PM) consisting of random copolymers of N-isopropylacrylamide (NIPA), methacrylic acid (MAA), and octadecyl acrylate (ODA) were prepared and characterized. The critical aggregation concentration, as determined by a fluorescence probe technique, was approximately 10 mg/L in water and phosphate-buffered saline. Phase transition pH was estimated at 5.7. The decrease in pH was accompanied by the destruction of hydrophobic clusters. Micelle size was dependent on temperature and the nature of the aqueous medium. The micelles were successfully loaded with a substantial amount of a photoactive anticancer drug, namely, aluminum chloride phthalocyanine (AlClPc). pH-responsive PM loaded with AlClPc were found to exhibit higher cytotoxicity against EMT-6 mouse mammary cells in vitro than control Cremophor EL formulation. These results show the potential of poly(NIPA-co-MAA-co-ODA) for in vivo administration of water-insoluble, photosensitizing anticancer drugs.

Acrylamides↗
PubMed2001

Azole-linked coumarin dyes as fluorescence probes of domain-forming polymers.

The binding of 7-aminocoumarins, substituted in the 3-position with heterocyclic benzimidazole or benzothiazole groups by domain-forming polymers in water has been studied. The acrylic polyelectrolyte, poly(methacrylic) acid (PMAA) was used as a solubilizing agent for coumarin dyes 6, 7, and 30 in water. The acid-base properties of these bound coumarin dyes were monitored spectroscopically on titration of aqueous solutions. Alterations in the fluorescence wavelength and intensity, quantum yields, lifetimes, and polarization are consistent with the preferential binding of the dyes in compact hydrophobic domains that form at a pH regime in which the polymer is in its protonated (uncharged) state. In this pH range (<4.0), coumarins 7 and 30 are bound as monocations, whereas coumarin 6 remains in its neutral form. Reduced quantum yields and lifetimes of fluorescence for cationic coumarins can be understood in terms of the imposition of a low-lying electron transfer state, an example of a twisted intramolecular charge transfer (TICT) intermediate. Effects of polymer microenvironment on the rate of TICT state decay (a reverse electron transfer) are observed. Coumarins of the azole type may find use as fluoroprobes of the microenvironments of proteins and other biological macromolecules and as agents for pH sensing.

Benzimidazoles↗
PubMed1998

Affinity precipitation of concanavalin A--studies of some underlying mechanisms using dynamic laser light scattering.

The final outcome of an affinity precipitation process will depend upon the efficiency of each individual stage involved: the formation of initial affinity complexes, the build-up of a precipitate and the elution of the target protein. Investigations on the first stage were done in this study utilizing a model system. The target protein was the lectin concanavalin A (Con A). Eudragit S-100, a reversibly soluble/insoluble polymer consisting of methyl methacrylate and methacrylic acid, to which the affinity ligand p-aminophenyl-alpha-D-glucopyranoside was coupled, served as the bifunctional ligand (ligand-Eudragit). Owing to the tetrameric structure of Con A, where each subunit has the ability to bind one sugar moiety, and to the multivalency of ligand-Eudragit, a network was formed between the Con A and ligand-Eudragit. It was possible to detect the initial soluble complexes formed by dynamic laser light scattering (DLLS) long before any precipitate could be analysed by transmittance measurements. The rate of complex formation was highly dependent on the ratio between lectin and ligand-Eudragit. It was further shown that the system did not reach equilibrium within the 110 min studied. When the complex formation was studied in the presence of glucose, the build-up rate was decreased to different degrees depending on the sugar concentration used. At high glucose concentrations the complex formation was completely inhibited.

Affinity Labels↗
PubMed2005

Thermoresponsive comb-shaped copolymer-Si(100) hybrids for accelerated temperature-dependent cell detachment.

Well-defined comb-shaped copolymer-Si(100) hybrids were prepared, via successive surface-initiated atom transfer radical polymerizations (ATRPs) of glycidyl methacrylate (GMA) and N-isopropylacrylamide (NIPAAm), for accelerated cell detachment at a lower temperature. The Si-C bonded comb copolymer consisted of a well-defined (nearly monodispersed) poly(glycidyl methacrylate) (P(GMA)) main chain, a well-defined NIPAAm polymer (P(NIPAAm) block, and well-defined P(NIPAAm) side chains. The ring opening reaction of epoxy groups of the P(GMA) main chain with 2-chloropropionic acid resulted in the immobilization of the alpha-chloroester groups (the ATRP initiators for the NIPAAm side chains) and the concomitant formation of hydroxyl groups. P(NIPAAm) acted as the thermoresponsive side chains of the comb copolymer for control of cell adhesion and detachment, while the P(GMA) main chain with hydroxyl groups provided a local hydrophilic microenvironment. The unique microstructure of the comb copolymer brushes facilitated cell recovery at 20 degrees C (below the lower critical solution temperature (LCST) of P(NIPAAm)) without restraining cell attachments and growth at 37 degrees C. The accelerated detachment of cells indicated that the underlying hydrophilic environment of the comb copolymer brushes contributed to speedy hydration of the P(NIPAAm) segments below the LCST. The thermoresponsive comb copolymer-Si(100) hybrids are potentially useful as adhesion modifiers for cells in silicon-based biomedical devices.

3T3 Cells↗
PubMed1984

Ion-exchange derivatives of Spheron. V. Sulphate and sulpho derivatives.

Using various reactions, strongly acidic derivatives of Spheron of the sulphate and sulpho types were prepared with nominal capacities between 0.37 and 2.0 mequiv./g. They were characterized by their capacities for small ions, by their static and dynamic capacities for proteins, by elemental analysis, by their working volumes and specific internal surface areas. The differences between the nominal capacities calculated theoretically from the sulphur contents and the measured values are discussed, as are the relationships between the nominal capacities for small ions and the static and dynamic capacities for proteins. The chromatographic properties of the cation exchangers are illustrated by the separation of an artificial mixture of proteins (serum albumin, chymotrypsinogen and lysozyme) at various pH values, and of a natural mixture of egg-white proteins. The separation of active enzymes is also reported. Sulphobutyl-Spheron was tested also as a catalyst for the esterification of alcohols.

Animals↗
PubMed2001

Eudragits: role as crystallization inhibitors in drug-in-adhesive transdermal systems of estradiol.

A transdermal steroidal delivery system usually contains a high concentration of drug to obtain high drug fluxes. The present investigation involved the development of drug-in-adhesive transdermal systems of estradiol using synthesized acrylate copolymer (EA) of 2-ethylhexyl acrylate and acrylic acid. The effect of several variables such as varying drug polymer ratios, effect of Eudragit RL PO and Eudragit E PO and effect of drying temperatures on prevention of drug crystallization in the formulation matrix was investigated. The systems free from drug crystals were evaluated and compared with a marketed formulation with respect to its skin permeation profile. The optimized formulation was also subjected to accelerated stability testing. Eudragit RL PO and Eudragit E PO were found to be effective as crystallization inhibitors in the transdermal matrix systems tested. Formulations fabricated with Eudragit E PO gave transparent systems with good film properties and a higher skin permeation profile as compared to that of the marketed system. Higher temperature and humidity conditions facilitated the formation of drug crystals, whereas no crystals were observed in the formulation matrix at 23+/-0.5 degrees C and at 30+/-1 degrees C for the period of 6 months studied.

Adhesives↗