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At least 775 records · Page 43Linked to original sources
PubMed2002

Formulation optimization and stability study of transdermal therapeutic system of nicorandil.

The aim of this research investigation was to fabricate acrylate-based stable transdermal therapeutic system (TTS) of nicorandil, which could deliver drug through transdermal route. Monolithic TTS was fabricated in pressure sensitive adhesives (PSAs)--(a) terpolymer (PSA1) of 2-ethylhexyl acrylate, methyl methacrylate, and acrylic acid, (b) copolymer (PSA2) of 2-ethylhexyl acrylate, methyl methacrylate, acrylic acid, and vinyl acetate, and (c) Eudragit E100 pressure sensitive adhesive (PSA3). To enhance the flux of nicorandil, skin permeation enhancer N-methyl-2-pyrrolidone (NMP) was investigated at different concentrations (0.05-5%) in PSAs. Fabricated TTS was evaluated for in-vitro release and skin permeation through guinea pig skin. Maximum flux of nicorandil was observed from Eudragit E100 based TTS and kept for stability study at refrigeration, 25 degrees C/30% RH and 30 degrees C/60% RH. Patches were evaluated for various physicochemical parameters. Formulation was observed to be relatively more stable at refrigeration. Shelf life of the formulation was found to be 270, 270, and 30 days at refrigeration, 25 degrees C/30% RH and 30 degrees C/60% RH conditions, respectively. Nicorandil could be successfully derived from Eudragit E100 based TTS, but attention needs to be given to improve its chemical stability in formulation.

Acrylates↗
PubMedDate not supplied

Recognition and selective binding of DNA by ionenes of different charge density.

The ability of aliphatic ionenes to recognize and bind DNA or poly(methacrylic acid) (PMA) in the equimolar mixture of these polyanions was studied by fluorescence quenching technique. Within a particular system, the selectivity of competitive interactions was shown to be determined by a component with the lowest degree of polymerization (DP). Ionene polycations with lowest DP values did not exhibit pronounced selectivity in binding DNA or PMA with higher values of DP. Increase in ionene DP resulted in a steady increase in selectivity of interaction and ultimately in almost exclusive binding of one of the two polyanions. The ability of the ionene to recognize and bind DNA in the mixture of polyanions was shown not to correlate with the affinity of the ionene to DNA in their binary mixture. Although ionenes with a higher charge density exhibited preferential binding to PMA, the ionenes with the lowest charge density selectively bound DNA.

Biocompatible Materials↗
PubMed2004

Modification of a supported lipid bilayer by polyelectrolyte adsorption.

Addition of a weak polyelectrolyte, poly(methacrylic acid) (PMA), to a supported phospholipid bilayer made from 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) depresses the melting temperature and alters the morphology of the bilayer in the gel phase. Ellipsometry measurements show that PMA adsorption lowers the phase transition temperature by 2.4 degrees C. Atomic force microscopy (AFM) showed no visible contrast in the fluid phase (above the melting temperature) but a rich morphology in the gel phase. In the gel phase, adsorption leads to formation of significantly less mobile phospholipid islands and other defects. One consequence of this lower mobility is a decrease in the implied cooperativity number of the phase transition, N, when polymer is added. Additionally, AFM images of the gel-phase bilayer show a highly defected structure that anneals significantly more slowly than in the absence of adsorbed polymer. Tentatively, we suggest that PMA preferentially decorates island and defect edges of the DMPC bilayer.

Adsorption↗
PubMed2001

A systematic examination of the morphogenesis of calcium carbonate in the presence of a double-hydrophilic block copolymer.

In this paper, a systematic study of the influence of various experimental parameters on the morphology and size of CaCO3 crystals after room-temperature crystallization from water in the presence of poly(ethylene glycol)-block-poly(methacrylic acid) (PEG-b-PMAA) is presented. The pH of the solution, the block copolymer concentration, and the ratio [polymer]/[CaCO3] turned out to be important parameters for the morphogenesis of CaCO3, whereas a moderate increase of the ionic strength (0.016 M) had no influence. Depending on the experimental conditions, the crystal morphologies can be tuned from calcite rhombohedra via rods, ellipsoids or dumbbells to spheres. A morphology map is presented which allows the prediction of the crystal morphology from a combination of pH, and CaCO3 and polymer concentration. Morphologies reported in literature for the same system but under different crystallization conditions agree well with the predictions from the morphology map. A closer examination of the growth of polycrystalline macroscopic CaCO3 spheres by TEM and time-resolved dynamic light scattering showed that CaCO3 macrocrystals are formed from strings of aggregated amorphous nanoparticles and then recrystallize as dumbbell-shaped or spherical calcite macrocrystal.

Calcium Carbonate↗
PubMed2001

Cytotoxicity of dental composite components and mercury compounds in pulmonary cells.

The cytotoxic potentials of the dental composite components triethyleneglycoldimethacrylate (TEGDMA) and 2-hydroxy-ethylmethacrylate (HEMA) as well as mercuric chloride (HgCl2) and methyl mercury chloride (MeHgCl) were investigated. Proliferating A549 and L2 cell monolayers were cultured in the absence or presence of composite components or mercurials. Twenty-four hours later the tetrazolium salt XTT (sodium 3'-[1-phenyl-aminocarbonyl)-3,4-tetrazolium]bis(4-methoxy-6-nitro)benzenesulphonic acid) was added. Formazan formation was quantified using a microtiter plate reader. EC50 values were obtained as half-maximum-effect concentrations from fitted curves. EC50 values were in A549 cells (mean values +/- standard deviation; n = 12; micromol/l); HEMA 8854+/-1882; TEGDMA 1821+/-529; HgCl2 41+/-7 and MeHgCl 27+/-3. EC50 values in L2 cells were: HEMA 191+/-28; TEGDMA 112+/-16; HgCl2 25+/-6 and MeHgCl 8+/-6. All tested substances induced a dose-dependent loss of viability in A549 and L2 cells after 24 h. The EC50 values of both mercurials were significantly (p < 0.05) lower compared to the values of both composite components. TEGDMA was about 5-fold (A549 cells) and about 2-fold (L2 cells) more toxic compared to HEMA. It is to be assumed that the risk of lung cell damage by dental composite components is even more unlikely.

Acrylic Resins↗
PubMed2002

Physicochemical behavior and cytotoxic effects of p(methacrylic acid-g-ethylene glycol) nanospheres for oral delivery of proteins.

The challenges faced to orally deliver therapeutic agents with unfavorable physicochemical properties, such as proteins, have been the primary motivation for the design and development of novel oral delivery systems that could circumvent biological barriers. In this work, we examined complexation-sensitive hydrogel nanospheres composed of poly[methacrylic acid-grafted-poly(ethylene glycol)] (P(MAA-g-EG)), on a model biological environment. For this purpose, a gastrointestinal cell culture model, the Caco-2 cell line, was employed to investigate the cytotoxic effects of the polymeric carrier and its effects on the cell monolayer integrity. The determination of the cytotoxic effects of the polymer network on the cell monolayer was performed by a colorimetric assay and by the counting of viable cells using the trypan blue exclusion method. Electrophysiological measurements were performed to measure the transepithelial electrical resistance changes in the monolayers in the presence and absence of the nanosphere suspension. The examination of the physicochemical interactions of the P(MAA-g-EG) nanosphere system with Caco-2 cell monolayers revealed that these systems possessed low cytotoxicity and were capable of opening the tight junctions between epithelial cells, therefore significantly reducing the transepithelial electrical resistance.

Administration, Oral↗
PubMed2004

Exceptional gas permeation selectivity of a glued Langmuir-Blodgett bilayer by pH control.

The monolayer properties of 5,11,17,23,29,35-hexakis[(N,N,N-trimethylamonium)-N-methyl-37,38,39,40,41,42-hexakis-n-hexadecyloxy-calix[6]arene hexachloride (1) have been characterized over aqueous solutions of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) as a function of pH. At high pH values (e.g., pH 10), such monolayers show relatively low surface viscosities. At low pH (e.g., pH 4.4), these monolayers exhibit relatively high surface viscosities. The barrier properties of single Langmuir-Blodgett bilayers of 1, which have been ionically cross-linked (i.e., "glued together") with PAA were found to correlate with changes in surface viscosity. Thus, bilayers that were fabricated under low pH conditions exhibited high permeation barriers and high permeation selectivity with respect to He and N(2). Given the extreme thinness of these glued bilayers (ca. 6 nm), the optimized He/N(2) selectivity of ca. 1000 is extraordinary. These results, taken together, demonstrate the feasibility of fine tuning the surface viscosity of monolayers of 1, and also the barrier properties of corresponding glued bilayers, by adjusting the pH of an aqueous subphase that contains a weak polyacid.

Acrylic Resins↗
PubMed1994

Two-dimensional high-performance liquid chromatography using monodisperse polymer beads containing segregated chemistries prepared by pore size specific functionalization. Single-column combinations of size exclusion or ion exchange with reversed-phase chromatography.

Separation media for the complete separation of complex samples that require a combination of size exclusion or ion-exchange with reversed-phase chromatographic modes in a single column have been prepared from size monodisperse 10 microns poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads using a pore size specific functionalization process. To achieve the first combination of chromatographic modes, the large pores of the beads were selectively hydrolyzed to diols using aqueous poly(styrenesulfonic acid), while highly hydrophobic octadecyl groups were introduced into the small pores by reaction of the remaining epoxide groups with octadecylamine. These beads provide excellent protein recoveries and may be used for the direct injection separation of samples containing both hydrophilic proteins and hydrophobic drugs. Beads containing diethylamino groups in the large pores and octadecyl functionalities in the small pores were also prepared by size-selective modification. A plot of log k' against ionic strength of the mobile phase for these beads shows the absence of hydrophobic interactions and documents the clean ion-exchange mechanism of protein separation. Examination of the small pores in both types of separation media confirmed that their hydrophobicity was sufficient to allow the separations of small molecules in reversed-phase mode. Column packed with these dual-chemistry beads exhibited high efficiencies and were used successfully for the separations of proteins and alkylbenzenes or drugs.

Animals↗
PubMed2001

Synthesis and characterization of methacrylic derivatives of 5-amino salicylic acid with pH-sensitive swelling properties.

The purpose of this study is to develop novel colon-specific drug delivery systems with pH-sensitive swelling and drug release properties. Methacrylic-type polymeric prodrugs with different content levels of 5-amino salicylic acid (5-ASA) were synthesized by free radical copolymerization of metacrylic acid (MAA), polyethylene glycol monomethacrylate (PEGMA), and a methacrylic derivative of 5-ASA (methacryloyloxyethyl 5-amino salicylate [MOES]). The copolymers were characterized, and the drug content of the copolymers was determined. The effect of copolymer composition on the swelling behavior and hydrolytic degradation was studied in simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.2). The swelling and hydrolytic behavior of the copolymers was dependent on the content of MAA groups and caused a decrease in gel swelling in SGF or an increase in gel swelling in SIF. Drug release studies showed that increasing content of MAA in the copolymer enhances the hydrolysis in SIF but has no effect in SGF. The results suggest that hydrogen-bonded complexes are formed between MAA and PEG pendant groups and that these pH-sensitive systems could be useful for preparation of a controlled-release formulation of 5-ASA.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2002

Preparation of poly(methacrylic acid-g-poly(ethylene glycol)) nanospheres from methacrylic monomers for pharmaceutical applications.

Nanospheres of poly(methacrylic acid-grafted-poly(ethylene glycol)) were prepared by solution/precipitation polymerization. As colloidal drug delivery carriers, they present unique properties that render them promising candidates for oral protein delivery. The polymerization was carried out in water and the resulting suspension was freeze-dried. As with many colloidal systems, the freeze-dried suspension showed strong agglomeration after drying. The effects of preparation conditions on the particle size and redispersion were investigated using photon correlation spectroscopy. Furthermore, the ability of different types and concentrations of stabilizers (cryoprotectants and steric stabilizers) in preventing this phenomenon was addressed. Pluronics, block copolymers widely used as nonionic surfactants, were the most effective in stabilizing the particles during the freeze-drying process. Pluronic P123, however, increased significantly the particle size of the nanospheres. On the other hand, lyophilizates obtained in the presence of Pluronic F68 had good redispersion properties and no change in particle size was observed.

Drug Compounding↗
PubMed2006

Balance of hydrophobic and electrostatic forces in the pH response of weak polyelectrolyte capsules.

A detailed study of the role of solution pH and ionic strength on the swelling behavior of capsules composed of the weak polyelectrolytes poly(4-vinylpyridine) (P4VP) and poly(methacrylic acid) (PMA) with different numbers of layers was carried out. The polyelectrolyte layers were assembled onto silicon oxide particles and multilayer formation was followed by zeta-potential measurements. Hollow capsules were investigated by scanning electron microscopy and atomic force microscopy. The pH-dependent behavior of P4VP/PMA capsules was probed in aqueous media using confocal laser scanning microscopy. All systems exhibited a pronounced swelling at the edges of stability, at pHs of 2 and 8.1. The swelling degree increased when more polymer material was adsorbed. The swollen state can be attributed to uncompensated positive and negative charges within the multilayers, and it is stabilized by counteracting hydrophobic interactions. The swelling was related to the electrostatic interactions by infrared spectroscopy and zeta-potential measurements. The stability of the capsules as well as the swelling degree at a given pH could be tuned, when the ionic strength of the medium was altered.

Biophysics↗
PubMed1989

Inhibition of bacterial growth under composite restorations following GLUMA pretreatment.

The purpose of this investigation was to test in five adult monkeys the effects of a glutaraldehyde-containing dentin bonding agent, GLUMA, on bacterial colonization in Class V cavities restored with composite resin. Experimental groups consisted of immediate placement of GLUMA and composite resin as well as placement of GLUMA or Scotchbond (control) in acid-etched cavities that had been left open to the oral environment for 48 hours. Various procedures for pretreatment of the cavities were included. Tissue specimens were prepared for light microscopy for observation of bacterial presence and pulp tissue reactions after eight days and 90 days. Bacteria were not detected in any of the 54 cavities treated with GLUMA regardless of observation period or use of enamel-etching procedure prior to placement of composite resin. When cavities were restored with composite resin without prior GLUMA pretreatment or with Scotchbond, bacteria were present under the majority of restorations at both time intervals. Pulpal inflammation of varying extent and character was seen after eight days in teeth that had been previously infected. At 90 days, pulps showed repair and healing regardless of treatment protocol. Data indicate that GLUMA has a distinct in vivo antibacterial effect that seems to prevent bacterial growth in tooth/restoration interfaces.

Aldehydes↗
PubMed2005

Cellular evaluation of oral chemotherapy carriers.

Hydrogel nanospheres composed of methacrylic acid and poly(ethylene glycol) were loaded with bleomycin and tested as a potential oral delivery system for chemotherapeutic agents. The gastrointestinal epithelium was modeled through the use of Caco-2 monolayers for studies of permeation enhancement by the carriers as well as bleomycin transport. Bleomycin efficacy following release from the carrier was evaluated with a DLD-1 tumor cell model. The nanospheres release bleomycin in response to a pH increase similar to that seen when passing from the stomach into the upper small intestine. These carriers can also increase the permeability of a model of the epithelial barrier, which would hopefully improve drug transport into the bloodstream. Efficacy studies using a tumor cell model showed retention of activity for bleomycin following loading and release from the nanospheres. The carriers described performed well during in vitro evaluation and can hopefully expand the spectrum of chemotherapeutic agents capable of being administered orally.

Administration, Oral↗
PubMed2004

Effect of salt concentration on the nanostructure of weak polyacid brush in the amphiphilic polymer monolayer at the air/water interface.

The effect of salt concentration on the nanostructure of a spread monolayer of ionic amphiphilic diblock copolymer, (diethylsilacyclobutane)m-b-(methacrylic acid)n, at the air-water interface was directly investigated by in situ X-ray reflectivity and neutron reflectivity techniques. Previously, we had found that a poly(methacrylic acid) (PMAA) hydrophilic layer under the water was not in the form of a simple polyelectrolyte brush but consisted of a dense carpet upper layer and a diffuse brush lower layer when the hydrophilic chain was long enough. Here we observed this double layer formation in the monolayer in aqueous NaCl solution at a constant surface pressure. The effect of salt added to the subphase differed with the salt concentrations, that is, below or above 0.1 M. In the presence of NaCl up to 0.1 M, both the hydrophobic layer and brush layer thicknesses decreased. On the other hand, both of them increased in the presence of NaCl above 0.1 M. Also, the carpet layer thickness was almost constant independent of the salt concentration. In addition, the brush top roughness showed a maximum in the presence of 0.1 M NaCl. The increase of the charge number on the PMAA chain and the screening effect of the Coulomb interaction by added salt ions were considered to be responsible for these phenomena.

Air↗
PubMed2002

Surface treatment of dentin with GLUMA and iron compounds for bonding indirect restorations.

The purpose of this study was to evaluate five dentin bonding systems simulating indirect restorations. The surface of bovine and human dentin was primed with a glutaraldehyde agent (GLUMA) and placed in a humidor at 37 degrees C for 168 h. In an experimental bonding system (GLUMA/CY/SB), the surfaces were etched with phosphoric acid, primed with cytochrome c, and then bonded to an acrylic rod with a self-curing resin (4-META/MMA-TBB). Specimens using two commercially available bonding systems [All-Bond 2 (AB2) and Super-Bond C & B (10-3/SB)] and two controls with and without GLUMA (GLUMA/10-3/SB and CY/SB) were also prepared. Tensile testing revealed that the bond strengths were influenced by the bonding system, 168 h dentin exposure and their interaction, but not by the tooth origin. AB2 showed the lowest bond strength. With the 10-3/SB system, exposing the dentin to humidity resulted in a decrease in bond strength. After 168 h of exposure, no significant differences were observed between 10-3/SB and CY/SB. The most effective bonding was obtained with the bonding systems of GLUMA/10-3/SB and GLUMA/CY/SB. Improved outcome is expected with these bonding systems when building up abutment teeth with indirect restorations.

Analysis of Variance↗
PubMedDate not supplied

Evaluation of dental adhesive systems with amalgam and resin composite restorations: comparison of microleakage and bond strength results.

A variety of laboratory tests have been developed to assist in predicting the clinical performance of dental restorative materials. Additionally, more than one methodology is in use for many types of tests performed in vitro. This project assessed and compared results derived from two specific laboratory testing methods, one for bond strength and one for microleakage. Seven multi-purpose dental adhesives were tested with the two methodologies in both amalgam and resin composite restorations. Bond strength was determined with a punch-out method in sections of human molar dentin. Microleakage was analyzed with a digital imaging system (Image-Pro Plus, Version 1.3) to determine the extent of dye penetration in Class V preparations centered at the CEJ on both the buccal and lingual surfaces of human molar teeth. There were 32 treatment groups (n = 10); seven experimental (dental adhesives) and one control (copal varnish, 37% phosphoric acid) followed by restoration with either amalgam or resin composite. Specimens were thermocycled 500 times in 5 degrees and 55 degrees C water with a one-minute dwell time. Bond strength and microleakage values were determined for each group. ANOVA and Student-Newman-Keuls tests demonstrated an interaction between restorative material and adhesive system with a significant difference among adhesives (p < 0.05). Using a multi-purpose adhesive system resulted in both a statistically significant increase in bond strength and a statistically significant decrease in extent of microleakage (p < 0.05). The effect of the adhesive upon both microleakage and bond strength was greater in the resin composite restorations than in the amalgam restorations. Bond strength testing was more discriminating than microleakage evaluation in identifying differences among materials.

Analysis of Variance↗
PubMed1992

An in vitro comparative analysis: scanning electron microscopy of dentin/restoration interfaces.

One hundred maxillary premolar teeth were randomly allocated to ten groups. Each group was restored with one of ten different restorative techniques. The teeth were stored in deionized water for 7d prior to longitudinal sectioning in a mesio-distal plane. Following sectioning, ten specimens from each group were chosen at random from the 20 available sections. The sectioned surfaces were polished using 600-grit SiC abrasive paper and etched for 10 s with 50% phosphoric acid to remove the smear layer produced by sectioning. Five tooth sections from the dentin bonding resin groups were allowed to dry at 20 degrees C for 24h. The glass ionomer-based groups were reimmersed in deionized water during this period. The remaining five sections from each group were replicated using an addition-cure vinyl polysiloxane impression material and an epoxy resin. A comparison was made of the sections and the replicas. All tooth specimens were sputter-coated with gold for 4 min and examined using a scanning electron microscope. Replicas were gold-coated for 3 min. Different tooth/restoration interfaces, associated with different materials, were observed. A marked difference between the replicas and tooth sections was observed for glass ionomer-based restorations but not for resin-based bonding systems. Representative samples of replicas and specimens are shown, and the significance of the observed differences is discussed.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1999

Investigation of plasma protein adsorption on functionalized nanoparticles for application in apheresis.

Particles with specific ligands for the adsorption of plasma proteins can be used in therapeutic or preparative apheresis. The development of these particles may benefit from an improved knowledge of the relationship between protein adsorption and the structure of ligands. Nanoparticles were functionalized with aliphatic diamines of increasing chain length; with the amino acids lysine, tryptophan, histidine, and their corresponding amines; and with tryptophan and histidine spaced with diamines of different length. Suitable protocols were developed for the washing of particles and the subsequent desorption of proteins adsorbed from human plasma. The adsorption pattern, as well as the quantification of the overall adsorption of proteins on these modified particles, was investigated with gel electrophoresis. This was followed by immunoblotting which yielded specific assessments of bound human serum albumin and fibrinogen. The comparison of protein adsorption with surface charge density and measured hydrophobicities yielded no simple correlations although in general more hydrophobic ligands bound higher quantities of protein. The detection of human serum albumin yielded similar results because it was observed for overall protein adsorption while the adsorption of fibrinogen expressed a different pattern. In this case, particular nanoparticles functionalized with aliphatic diamines bound significantly higher amounts of fibrinogen than all other ligands.

Adsorption↗