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Roland Bodmeier - One of the best experts on this subject based on the ideXlab platform.
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optimised process and formulation conditions for extended release dry polymer powder coated pellets
European Journal of Pharmaceutics and Biopharmaceutics, 2010Co-Authors: Ildiko Terebesi, Roland BodmeierAbstract:Abstract The objective of this study was to improve the film formation and permeability characteristics of extended release ethylcellulose coatings prepared by dry polymer powder coating for the release of drugs of varying solubility. Ethylcellulose (7 and 10 cp viscosity grades) and Eudragit® RS were used for dry powder coating of pellets in a fluidised bed ball coater. Pre-plasticised ethylcellulose powder was prepared by spray-drying aqueous ethylcellulose dispersions (Surelease® and Aquacoat®) or by hot melt extrusion/cryogenic grinding of plasticised ethylcellulose. Chlorpheniramine maleate and theophylline were used as model drugs of different solubilities. The film formation process, polymeric films and coated pellets were characterised by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM) and dissolution testing. Film formation and extended drug release was achieved with ethylcellulose, a polymer with a high glass transition temperature ( T g ) without the use of water, which is usually required in dry powder coating. DMA-measurements revealed that plasticised ethylcellulose had a modulus of elasticity ( E ′) similar to the low T g Eudragit® RS. With increasing plasticiser concentration, the T g of ethylcellulose was reduced and the mechanical properties improved, thus facilitating coalescence of the polymer particles. SEM-pictures revealed the formation of a dense, homogeneous film. The lower viscosity grade ethylcellulose (7 cp) resulted in better film formation than the higher viscosity grade (10 cp) and required less stringent curing conditions. Successful extended release ethylcellulose coatings were also obtained by coating with pre-plasticised spray-dried ethylcellulose powders as an alternative to the separate application of pure ethylcellulose powder and plasticiser. The permeability of the extended release coating could be controlled by using powder blends of ethylcellulose with the hydrophilic polymer HPMC. In conclusion, dry polymer powder coating is an interesting technique to achieve extended release of drugs with varying solubility as an alternative to classical coatings obtained from organic polymer solution or aqueous polymer dispersions.
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coating of pellets with micronized ethylcellulose particles by a dry powder coating technique
International Journal of Pharmaceutics, 2003Co-Authors: Nantharat Pearnchob, Roland BodmeierAbstract:Abstract Pellets were coated with ethylcellulose powder to achieve extended release. The film forming ability of ethylcellulose powder and the effect of formulation factors (plasticizer type and concentration) and curing conditions (curing temperature and time) were investigated. The coating formulation was divided into two components consisting of a powder mixture (polymer plus talc) and a mixture of liquid materials (plasticizer plus binder solution), which were sprayed separately into the coating chamber of a fluidized bed coater (Glatt® GPCG-1, Wurster insert). The coated pellets were oven-cured under different conditions (60–80 °C, 2–24 h) without and with humidity (100% relative humidity). Propranolol hydrochloride was used as a model drug, and drug release was studied in 0.1N HCl at 37 °C (USP XXV paddle method). Despite the high glass transition temperature of ethylcellulose (133.4 °C), micronized ethylcellulose powder can be used for dry powder coating by adjusting the coating temperature, amount and type of plasticizer applied, and curing conditions. 40% plasticizer and a curing step (80 °C, 24 h) were required to achieve complete coalescence of the polymer particles and extended drug release of coated pellets. Although ethylcellulose-coated pellets had an uneven surface, extended drug release could be obtained with coating level of 15%. Because of its high glass transition temperature, ethylcellulose-coated pellets showed unchanged drug release profiles upon storage at room temperature for 3 years.
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A novel multiple-unit sustained release indomethacin-hydroxypropyl Methylcellulose delivery system prepared by ionotropic gelation of sodium alginate at elevated temperatures
Carbohydrate Polymers, 2003Co-Authors: Roland Bodmeier, Ornlaksana PaeratakulAbstract:Abstract A multiple-unit indomethacin delivery system based on hydroxypropyl Methylcellulose as the hydrophilic carrier material was developed by a novel technique using the insolubility of the cellulose ether at elevated temperatures and the ionotropic gelation of the polysaccharide, sodium alginate with calcium ions. Spherical beads were prepared by dropping hot sodium alginate solution (60°C) containing dispersed drug and dispersed hydroxypropyl Methylcellulose into the heated calcium chloride solution. Beads with a combined hydroxypropyl Methylcellulose-indomethacin solids content of up to 98% could be prepared because of the processing of a hydroxypropyl Methylcellulose dispersion rather than a solution. The beads were characterized by dissolution and scanning electron microscopy. The drug release was controlled by the viscosity grade of the hydroxypropyl Methylcellulose and the rate of polymer gelation, and could be sustained over an 8-h period.
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ph independent release of a weakly basic drug from water insoluble and soluble matrix tablets
Journal of Controlled Release, 2000Co-Authors: A Streubel, J Siepmann, A Dashevsky, Roland BodmeierAbstract:Abstract Weakly basic drugs or salts thereof demonstrate pH-dependent solubility. The resulting release from conventional matrix tablets decreases with increasing pH-milieu of the gastrointestinal tract. The aim of this study was to overcome this problem and to achieve pH-independent drug release. Two different polymers were used as matrix formers, the water-insoluble and almost unswellable ethylcellulose (EC), and the water-soluble and highly swellable hydroxypropyl Methylcellulose (HPMC). Two different approaches to solve the problem of pH-dependent release of weakly basic drugs are demonstrated in this paper. The first one is based on the addition of hydroxypropyl Methylcellulose acetate succinate (HPMCAS, an enteric polymer), the second one on the addition of organic acids such as fumaric, succinic or adipic acid to the drug–polymer system. The first approach failed to achieve pH-independent drug release, whereas the addition of organic acids to both matrix formers was found to maintain low pH values within the tablets during drug release in phosphate buffer (pH 6.8 or 7.4). Thus, the micro-environmental conditions for the dissolution and diffusion of the weakly basic drug were almost kept constant. The release of verapamil hydrochloride from tablets composed of ethylcellulose or HPMC and organic acids was found to be pH-independent.
D D L Chung - One of the best experts on this subject based on the ideXlab platform.
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high electric permittivity of polymer modified cement due to the capacitance of the interface between polymer and cement
Journal of Materials Science, 2018Co-Authors: Min Wang, D D L ChungAbstract:The electric permittivity is a material property that relates to the dielectric and electromagnetic behaviors. This work reports the effect of polymer admixtures on the permittivity (2 kHz) of cement paste. The permittivity is increased significantly by the addition of either Methylcellulose (dissolved) or latex (styrene–butadiene, not dissolved), due to the capacitance of the interface between polymer and cement. The permittivity is effectively modeled by a material-level equivalent circuit model that comprises cement, polymer and cement/polymer interface in parallel. The series model is not effective. For both Methylcellulose and latex, the cement and cement/polymer interface dominate the contributions to the permittivity, while the polymer contributes little. The contributions of polymer and cement/polymer interface increase monotonically with increasing polymer/cement ratio, while the contribution of cement decreases monotonically. Methylcellulose at the highest proportion of 1.4% by mass of cement gives permittivity 52, whereas latex at the highest solid latex proportion of 14% by mass of cement gives permittivity 43. For the same polymer/cement ratio, the permittivity is much higher for Methylcellulose than latex. The difference between Methylcellulose and latex is due to the much greater contribution of the cement/polymer interface to the permittivity for Methylcellulose than latex, as caused by the nanoscale morphology of the Methylcellulose and the consequent large cement/polymer interface area. At the same polymer/cement ratio, the fractional contribution from the cement/polymer interface is greater for Methylcellulose than latex, though those from the polymer and cement are greater for latex than Methylcellulose.
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carbon fiber reinforced cement mortar improved by using acrylic dispersion as an admixture
Cement and Concrete Research, 2001Co-Authors: Jingyao Cao, D D L ChungAbstract:Cement mortar reinforced by short carbon fibers was improved by using acrylic dispersion as an admixture in the amount of 15% by mass of cement. The improvement of the tensile properties (particularly strength and ductility) was more than those attained by using Methylcellulose, styrene acrylic, or latex as admixtures. Acrylic was effective whether silica fume was present or not. However, for lowering the electrical resistivity, Methylcellulose in combination with silica fume was most effective.
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microstructural and mechanical effects of latex Methylcellulose and silica fume on carbon fiber reinforced cement
Aci Materials Journal, 1997Co-Authors: Pohsiu Che, D D L ChungAbstract:The effect of Methylcellulose, silica fume, and latex on the degree of dispersion of short carbon fibers in cement paste was assessed. This degree, as indicated by the ratio of the measured volume of electrical conductivity to the calculated value, and the effectiveness of the fibers in enhancing the tensile/flexural properties attained by using Methylcellulose and silica fume were higher than those attained by using Methylcellulose alone or latex. Methylcellulose was superior to latex in giving a high degree of fiber dispersion at fiber volume fractions < 1 percent, as measured by this technique. Latex resulted in superior tensile-flexural properties and lower content and size of air voids than Methylcellulose. With the fiber content fixed at 0.53 vol. percent, the degree of fiber dispersion, as measured by this technique, decreased with increasing latex-cement ratio. As a result the flexural toughness decreased monotonically with increasing latex-cement ratio and the flexural strength attained a maximum at an intermediate latex-cement ratio of 0.15. In contrast, both flexural toughness and strength increased monotonically with increasing latex-cement ratio when fibers were absent.
Dave Wallick - One of the best experts on this subject based on the ideXlab platform.
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Reviewing the use of ethylcellulose, Methylcellulose and hypromellose in microencapsulation. Part 3: Applications for microcapsules.
Drug development and industrial pharmacy, 2011Co-Authors: True L. Rogers, Dave WallickAbstract:This three-part review has been developed following the evaluation of literature where ethylcellulose, Methylcellulose, or hypromellose was used to make microcapsules. Parts 1 and 2 of the review are published in separate papers. Part 1 covers the various materials used to formulate microcapsules, and Part 2 covers the various techniques used to make microcapsules. In the current paper, Part 3 covers the end-use applications for which microcapsules are used. Examples of applications to be covered include modified release, improved efficacy and safety, multiparticulate compression, improved processability and stability, and taste- and odor-masking. It is hoped that formulators can use Part 3 to understand the various end-use applications of microcapsules made from these encapsulating polymers. SciFinder was utilized to perform the literature search. SciFinder leverages literature databases, such as Chemical Abstracts Service Registry and Medline. A total of 379 references were identified during the review....
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Reviewing the use of ethylcellulose, Methylcellulose and hypromellose in microencapsulation. Part 1: materials used to formulate microcapsules
Drug development and industrial pharmacy, 2011Co-Authors: True L. Rogers, Dave WallickAbstract:This review highlights references where ethylcellulose, Methylcellulose and hypromellose were used to make microcapsules. The review has been divided into three parts. This first part discusses various materials used to formulate microcapsules, such as the three encapsulating polymers as well as protective colloids, plasticizers and surfactants. The second part covers the various techniques used to make microcapsules, such as temperature-induced phase separation, emulsion solvent evaporation, solvent evaporation, film coating, and others. The third part covers the various applications for which microcapsules are used, such as modified release, improved efficacy and safety, taste- and odor-masking, and others. It is hoped that formulators can use Part 1 as a guide to the literature documenting formulation of microcapsules made from these encapsulating polymers. SciFinder was utilized to identify the pertinent literature. SciFinder leverages literature databases, such as Chemical Abstracts Service Registry ...
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Reviewing the use of ethylcellulose, Methylcellulose and hypromellose in microencapsulation. Part 2: Techniques used to make microcapsules
Drug development and industrial pharmacy, 2011Co-Authors: True L. Rogers, Dave WallickAbstract:This three-part review has been developed following the evaluation of literature where ethylcellulose, Methylcellulose or hypromellose was used to make microcapsules. Parts 1 and 3 of the review are published as separate papers. Part 1 covers the various materials used to formulate microcapsules, and Part 3 covers the various end-use applications for microcapsules. In the current paper, Part 2 covers the techniques used to make microcapsules. Examples of techniques to be covered include temperature-induced phase separation, emulsion solvent evaporation, solvent evaporation, film coating, nonsolvent addition and spray drying. It is hoped that formulators can use Part 2 to understand how to formulate microcapsules using these encapsulating polymers.SciFinder was utilized to perform the literature search. SciFinder leverages literature databases, such as Chemical Abstracts Service Registry and Medline. A total of 379 references were identified during the review. The need for a three-part review reflects the ...
Jean Paul Remon - One of the best experts on this subject based on the ideXlab platform.
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correlation between the permeability of metoprolol tartrate through plasticized isolated ethylcellulose hydroxypropyl Methylcellulose films and drug release from reservoir pellets
European Journal of Pharmaceutics and Biopharmaceutics, 2007Co-Authors: Patrick Rombout, Jean Paul Remon, Chris Vervaet, Guy Van Den MooterAbstract:The present study investigates if drug diffusion through plasticized isolated ethylcellulose (EC)/hydroxypropyl Methylcellulose (HPMC) films prepared by solvent casting can be used as a tool to develop spray-coated dosage forms. In particular, the importance of the level and type of plasticizers was investigated. The permeability of the model drug metoprolol tartrate through plasticized isolated films could be adjusted by selecting the type and amount of plasticizer in the films due to the different hydrophilicity of the plasticizers. The release of metoprolol tartrate from coated pellets is consistent with the drug diffusion through the films made up of the same polymer blends. This indicated that it is useful to test isolated films for early predictions and for formulation optimization.
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hot melt extruded ethylcellulose cylinders containing a hpmc gelucire core for sustained drug delivery
Journal of Controlled Release, 2004Co-Authors: Els Mehuys, Chris Vervaet, Jean Paul RemonAbstract:The objective of the study was to develop a sustained release system consisting of a hot-melt extruded ethylcellulose pipe surrounding a drug-containing hydroxypropyl Methylcellulose (HPMC)-Gelucire 44/14 core, yielding a monolithic matrix system applicable in the domain of sustained drug release. The influence of HPMC substitution type and viscosity grade was investigated through dissolution testing and erosion studies. All sustained release systems showed a nearly constant drug release profile with only 40% of the drug released after 24 h. To achieve complete drug release after 24 h, the core formulation and the dimensions of the hollow pipe were modified. Changing the composition of the core did not result in the intended zero-order drug release. Shortening the length of the ethylcellulose cylinder accelerated drug release, while modifying the diameter did not affect the drug release rate. The drug dissolution profile and the release mechanism were independent of drug solubility. Increasing the drug loading caused a small increase of the drug release rate, but did not alter the release mechanism.
Guimes Rodrigues Filho - One of the best experts on this subject based on the ideXlab platform.
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Instituto de Química, UFU
2016Co-Authors: Júlia G. Vieira, Guimes Rodrigues Filho, Carla Da S. Meireles, A A. C. Faria, Dayane D. Gomide, Daniel Pasquini, Rosana M. N. De Assunção, Leila A. De C. Motta, Faculdade De Engenharia CivilAbstract:Abstract: Methylcellulose was produced from the fibers of Mangifera indica L. Ubá mango seeds. MCD and MCI Methylcellulose samples were made by heterogeneous methylation, using dimethyl sulfate and iodomethane as alkylating agents, respectively. The materials produced were characterized for their thermal properties (DSC and TGA), crystallinity (XRD) and Degree of Substitution (DS) in the chemical route. The cellulose derivatives were employed as mortar additive in order to improve mortar workability and adhesion to the substrate. These properties were evaluated by means of the consistency index (CI) and bond tensile strength (TS) tests. The Methylcellulose (MCD and MCI) samples had CI increased by 27.75 and 71.54 % and TS increased by 23.33 and 29.78%, respectively, in comparison to the reference sample. Therefore, the polymers can be used to produce adhesive mortars
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characterization of Methylcellulose produced from sugar cane bagasse cellulose crystallinity and thermal properties
Polymer Degradation and Stability, 2007Co-Authors: Guimes Rodrigues Filho, Rosana Maria Nascimento De Assuncao, Carla Da Silva Meireles, Julia Graciele Vieira, Daniel Alves Cerqueira, Hernane Da Silva Barud, Sidney Jose Lima Ribeiro, Younes MessaddeqAbstract:Abstract In the present work, Methylcellulose produced from sugar cane bagasse was characterized by FTIR, WAXD, DTA and TGA techniques. Two samples were synthesized: Methylcellulose A and Methylcellulose B. The only difference in the process was the addition of fresh reactants during the preparation of Methylcellulose B. The ratio between the absorption intensities of the C–H stretching band at around 2900 cm −1 and O–H stretching at around 3400 cm −1 for Methylcellulose B is higher than for Methylcellulose A, indicating that Methylcellulose B showed an increase in the degree of substitution (DS). Methylcellulose A presents a more heterogeneous structure, which is similar to the original cellulose as seen through FTIR and DTA. Methylcellulose B showed thermal properties similar to commercial Methylcellulose. The modification of Methylcellulose preparation method allows the production of a material with higher DS, crystallinity and thermal stability in relation to the original cellulose and to Methylcellulose A.
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synthesis and characterization of Methylcellulose from sugar cane bagasse cellulose
Carbohydrate Polymers, 2007Co-Authors: Rose G P Viera, Guimes Rodrigues Filho, Rosana Maria Nascimento De Assuncao, Carla Da Silva Meireles, Julia Graciele Vieira, Grasielle S De OliveiraAbstract:Abstract In the present paper, Methylcellulose was produced from cellulose extracted of sugar cane bagasse, using dimethyl sulfate in heterogeneous conditions. The infrared spectra of the cellulose and of the Methylcellulose present significant differences at the regions from 3600 to 2700 cm −1 and from 1500 to 800 cm −1 . The ratio between the absorption intensities of the O H stretching band (∼3400 cm −1 ) and the C H stretching band (∼2900 cm −1 ) in the spectra of the methylated samples is lower than that in the cellulose spectrum, evidencing the methylation of the samples. The effect of using toluene and acetone during the synthesis was studied. Without using the solvent, the degree of substitution (DS) of the methylated sample was 0.70, reaching a DS of 1.2 when using acetone. The produced Methylcellulose presents chemical and physical properties that increase its range of application and aggregate value to this agro-industrial residue.
