The Experts below are selected from a list of 2073 Experts worldwide ranked by ideXlab platform
Roland Bodmeier - One of the best experts on this subject based on the ideXlab platform.
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drug release from and sterilization of in situ cubic phase forming Monoglyceride drug delivery systems
European Journal of Pharmaceutics and Biopharmaceutics, 2010Co-Authors: Abid Riaz Ahmed, A Dashevsky, Roland BodmeierAbstract:Since a Monoglyceride-based cubic phase is too viscous to be injected parenterally, mixtures of Monoglyceride, water and water-miscible cosolvents were investigated as low viscosity injectable in situ cubic phase-forming formulations. Upon contact with the release medium, a highly viscous cubic phase formed rapidly and served as an extended release matrix for the oligonucleotide drug. Extended drug release was obtained with all formulations. The drug release followed the square root of time relationship indicating a diffusion-controlled release mechanism. The release depended on the type of cosolvent and followed the order of ethanol > PEG 300 > 2-pyrrolidone > DMSO. Higher water or Monoglycerides contents decreased the drug release because of an increased viscosity and increased swollen matrix thickness. The bioburden of different commercially available Monoglycerides and of the prepared in situ cubic phase-forming formulations met USP XXIII requirements. Monoglycerides can be successfully sterilized by gamma irradiation or by autoclaving and the in situ cubic phase-forming formulations by autoclaving and aseptic filtration. The Monoglycerides and in situ cubic phase-forming formulations retained their phase behaviour and release properties after sterilization.
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effect of dissolution media and additives on the drug release from cubic phase delivery systems
Journal of Controlled Release, 1997Co-Authors: Chinming Chang, Roland BodmeierAbstract:Abstract Unsaturated Monoglycerides such as monooleate or monolinoleate form a physically stable, highly viscous cubic phase in contact with excess aqueous medium. The swelling and release properties of drug-loaded Monoglyceride matrices were evaluated with regard to the development of an oral sustained release delivery system. The swelling capacity of the amphiphilic Monoglyceride matrix was higher in 0.1 M pH 7.4 phosphate buffer than in 0.1 N HCl. However, the drug release was opposite in trend, with propranolol HCl being released at a slower rate in pH 7.4 buffer. This was attributed to the presence of free fatty acids in the Monoglyceride matrix, which were ionized at pH 7.4, but unionized in 0.1 N HCl. The formation of insoluble complexes with the cationic drug, propranolol HCl, at the higher pH explained the slower release. The incorporation of oleic acid in the Monoglyceride matrices further confirmed the influence of fatty acids and was a tool to manipulate the release of cationic drugs. The inclusion of oleic acid and propranolol HCl resulted in the concentration- and pH-dependent formation of other mesophases besides the cubic phase. Varying the ionic strength of the dissolution medium had a minor effect on both swelling and drug release from the nonionic, amphiphilic Monoglycerides. While the cubic phase stayed physically intact in enzyme-free simulated gastrointestinal fluids, the addition of bile salts to the pH 7.4 buffer resulted in the dispersion and disappearance of the swollen Monoglyceride phase.
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swelling of and drug release from Monoglyceride based drug delivery systems
Journal of Pharmaceutical Sciences, 1997Co-Authors: Chinming Chang, Roland BodmeierAbstract:Depending on the water content, unsaturated Monoglycerides form various liquid crystalline phases, which can be used as sustained-release carriers. The aim of this study was to investigate the water uptake of and drug release from melt-congealed Monoglyceride-based drug carriers. The water uptake of the unsaturated Monoglycerides monoolein and monolinolein followed second-order swelling kinetics and levelled off at about 50% water content, at which a highly viscous cubic phase was formed. The rapid formation of the cubic phase suggested that the drug release occurred mainly from this phase. The drug release followed the square-root of time relationship during the initial release phase. Chlor-pheniramine maleate, an amphiphilic drug was not completely released because of binding to the cubic phase. The rate of water uptake increased and the maximum water uptake decreased with increasing temperature. The drug release could be controlled by varying the surface-to-volume ratio, the drug loading, and the water content of the lipid matrix. It was independent of the source of monoolein.
Hyoe Hatakeyama - One of the best experts on this subject based on the ideXlab platform.
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preparation and characterization of polyurethane foams using a palm oil based polyol
Bioresource Technology, 2008Co-Authors: Ryohei Tanaka, Shigeo Hirose, Hyoe HatakeyamaAbstract:Polyurethane (PU) foams were prepared using a palm oil-based polyol (PO-p). At the first stage, palm oil was converted to Monoglycerides as a new type of polyol by glycerolysis. A yield of the product reached 70% at reaction temperature of 90 °C by using an alkali catalyst and a solvent. At the second stage, PU foams were prepared from mixtures of the polyol and polyethylene glycol (PEG) or diethylene glycol (DEG) and an isocyanate compound. Characterization of the foams was carried out by thermal and mechanical analyses. The analyses showed that the chain motion of polyurethane becomes more flexible at the higher PO-p content in the whole polymer, which indicates that the Monoglyceride molecules work as soft segments. The study here may lead to a development of a new type of polyurethane foams using palm oil as a raw material.
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preparation and characterization of polyurethane foams using a palm oil based polyol
Bioresource Technology, 2008Co-Authors: Ryohei Tanaka, Shigeo Hirose, Hyoe HatakeyamaAbstract:Polyurethane (PU) foams were prepared using a palm oil-based polyol (PO-p). At the first stage, palm oil was converted to Monoglycerides as a new type of polyol by glycerolysis. A yield of the product reached 70% at reaction temperature of 90 degrees C by using an alkali catalyst and a solvent. At the second stage, PU foams were prepared from mixtures of the polyol and polyethylene glycol (PEG) or diethylene glycol (DEG) and an isocyanate compound. Characterization of the foams was carried out by thermal and mechanical analyses. The analyses showed that the chain motion of polyurethane becomes more flexible at the higher PO-p content in the whole polymer, which indicates that the Monoglyceride molecules work as soft segments. The study here may lead to a development of a new type of polyurethane foams using palm oil as a raw material.
J. Isabel Di Cosimo - One of the best experts on this subject based on the ideXlab platform.
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mgo based catalysts for Monoglyceride synthesis from methyl oleate and glycerol effect of li promotion
Applied Catalysis A-general, 2011Co-Authors: Cristián Alejandro Ferretti, C R Apesteguia, J. Isabel Di CosimoAbstract:Abstract The synthesis of Monoglycerides (glyceryl monooleates) by heterogeneously catalyzed glycerolysis of an unsaturated fatty acid methyl ester (methyl oleate) was studied on MgO and Li-promoted MgO catalysts. Several MgO-based catalysts with different Li loadings were prepared by incipient wetness impregnation and characterized by XRD, N2 physisorption, and FTIR and TPD of CO2 among other techniques. Promotion of MgO with lithium, a basic promoter, affected the textural and structural properties of the resulting oxides so that more crystalline MgO phases with decreased surface area were obtained at increasing Li contents. Furthermore, the addition of Li generated new strong base sites because of formation of dispersed surface Li2O species, and thereby increased the total base site density of parent MgO. Li-containing MgO catalysts efficiently promoted the glycerolysis reaction, achieving high Monoglyceride yields (70–73%) at 493 K. The initial Monoglyceride formation rate increased linearly with the Li content on the sample following the enhanced overall catalyst base strength. Although conversions at the end of the run were ≈100% for all the catalysts, the Monoglyceride selectivity slightly decreased with the Li loading, probably as a consequence of the less surface affinity for glycerol adsorption that facilitates competing Monoglyceride re-adsorption and transformation to diglycerides by consecutive glycerolysis or disproportionation reactions.
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Monoglyceride synthesis by glycerolysis of methyl oleate on solid acid-base catalysts
Chemical Engineering Journal, 2010Co-Authors: Cristián Alejandro Ferretti, Agostina Soldano, J. Isabel Di CosimoAbstract:Abstract The synthesis of Monoglycerides by glycerolysis of methyl oleate, an unsaturated fatty acid methyl ester, was studied on acid–base solid catalysts as an alternative to the current commercial technology that uses liquid base catalysts. Initially, the reaction conditions such as catalyst particle size and stirring rate required for operating the four-phase semi-continuous reactor under a kinetically controlled-regime were determined. Then the optimization of the reaction parameters for achieving high Monoglyceride yields was performed using MgO. MgO compared favorably with the corresponding homogeneously catalyzed process. In fact, when using high reaction temperatures (493–523 K), glycerol/methyl oleate molar ratios between 2 and 6, and catalyst/reactant ratios of about 30 g/mol, glycerolysis of methyl oleate yields up to 77% Monoglycerides in 2 h, a much higher value than those usually obtained via the liquid base-catalyzed homogeneous process (40–60%). The acid–base site requirements for the glycerolysis reaction were investigated using single oxides with different electronegativities. A good correlation was found between the catalytic activity and the base site density. In addition, results show that glycerolysis of methyl oleate requires strong base sites such as those of MgO.
Ryohei Tanaka - One of the best experts on this subject based on the ideXlab platform.
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preparation and characterization of polyurethane foams using a palm oil based polyol
Bioresource Technology, 2008Co-Authors: Ryohei Tanaka, Shigeo Hirose, Hyoe HatakeyamaAbstract:Polyurethane (PU) foams were prepared using a palm oil-based polyol (PO-p). At the first stage, palm oil was converted to Monoglycerides as a new type of polyol by glycerolysis. A yield of the product reached 70% at reaction temperature of 90 °C by using an alkali catalyst and a solvent. At the second stage, PU foams were prepared from mixtures of the polyol and polyethylene glycol (PEG) or diethylene glycol (DEG) and an isocyanate compound. Characterization of the foams was carried out by thermal and mechanical analyses. The analyses showed that the chain motion of polyurethane becomes more flexible at the higher PO-p content in the whole polymer, which indicates that the Monoglyceride molecules work as soft segments. The study here may lead to a development of a new type of polyurethane foams using palm oil as a raw material.
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preparation and characterization of polyurethane foams using a palm oil based polyol
Bioresource Technology, 2008Co-Authors: Ryohei Tanaka, Shigeo Hirose, Hyoe HatakeyamaAbstract:Polyurethane (PU) foams were prepared using a palm oil-based polyol (PO-p). At the first stage, palm oil was converted to Monoglycerides as a new type of polyol by glycerolysis. A yield of the product reached 70% at reaction temperature of 90 degrees C by using an alkali catalyst and a solvent. At the second stage, PU foams were prepared from mixtures of the polyol and polyethylene glycol (PEG) or diethylene glycol (DEG) and an isocyanate compound. Characterization of the foams was carried out by thermal and mechanical analyses. The analyses showed that the chain motion of polyurethane becomes more flexible at the higher PO-p content in the whole polymer, which indicates that the Monoglyceride molecules work as soft segments. The study here may lead to a development of a new type of polyurethane foams using palm oil as a raw material.
Chinming Chang - One of the best experts on this subject based on the ideXlab platform.
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effect of dissolution media and additives on the drug release from cubic phase delivery systems
Journal of Controlled Release, 1997Co-Authors: Chinming Chang, Roland BodmeierAbstract:Abstract Unsaturated Monoglycerides such as monooleate or monolinoleate form a physically stable, highly viscous cubic phase in contact with excess aqueous medium. The swelling and release properties of drug-loaded Monoglyceride matrices were evaluated with regard to the development of an oral sustained release delivery system. The swelling capacity of the amphiphilic Monoglyceride matrix was higher in 0.1 M pH 7.4 phosphate buffer than in 0.1 N HCl. However, the drug release was opposite in trend, with propranolol HCl being released at a slower rate in pH 7.4 buffer. This was attributed to the presence of free fatty acids in the Monoglyceride matrix, which were ionized at pH 7.4, but unionized in 0.1 N HCl. The formation of insoluble complexes with the cationic drug, propranolol HCl, at the higher pH explained the slower release. The incorporation of oleic acid in the Monoglyceride matrices further confirmed the influence of fatty acids and was a tool to manipulate the release of cationic drugs. The inclusion of oleic acid and propranolol HCl resulted in the concentration- and pH-dependent formation of other mesophases besides the cubic phase. Varying the ionic strength of the dissolution medium had a minor effect on both swelling and drug release from the nonionic, amphiphilic Monoglycerides. While the cubic phase stayed physically intact in enzyme-free simulated gastrointestinal fluids, the addition of bile salts to the pH 7.4 buffer resulted in the dispersion and disappearance of the swollen Monoglyceride phase.
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swelling of and drug release from Monoglyceride based drug delivery systems
Journal of Pharmaceutical Sciences, 1997Co-Authors: Chinming Chang, Roland BodmeierAbstract:Depending on the water content, unsaturated Monoglycerides form various liquid crystalline phases, which can be used as sustained-release carriers. The aim of this study was to investigate the water uptake of and drug release from melt-congealed Monoglyceride-based drug carriers. The water uptake of the unsaturated Monoglycerides monoolein and monolinolein followed second-order swelling kinetics and levelled off at about 50% water content, at which a highly viscous cubic phase was formed. The rapid formation of the cubic phase suggested that the drug release occurred mainly from this phase. The drug release followed the square-root of time relationship during the initial release phase. Chlor-pheniramine maleate, an amphiphilic drug was not completely released because of binding to the cubic phase. The rate of water uptake increased and the maximum water uptake decreased with increasing temperature. The drug release could be controlled by varying the surface-to-volume ratio, the drug loading, and the water content of the lipid matrix. It was independent of the source of monoolein.