Effect of temperature-increase rate on drug release characteristics of dextran microspheres prepared by emulsion solvent evaporation process

Miyazaki, Yasunori; Onuki, Yoshinori; Yakou, Shigeru; Takayama, K.

doi:10.1016/j.ijpharm.2006.06.003

Cited by 38 publications

(17 citation statements)

References 20 publications

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“…Rapid solvent removal allows the polymer to precipitate quickly, entrapping most of the drug within the polymer matrix 29. Applying reduced pressure30,31 or increasing the temperature32–34 can expedite solvent removal. Elevated temperature, however, can result in low particle yield, larger particle size, decreased encapsulation efficiency, and coarser morphology 33.…”

Section: Discussionmentioning

confidence: 99%

Core fucosylation is required for midline patterning during zebrafish development

Seth

Machingo

Fritz

et al. 2010

Developmental Dynamics

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Complex carbohydrates represent one of the most polymorphic classes of macromolecules, but their functions during embryonic development remain poorly defined. Herein, we show that knockdown of FucT8, the fucosyltransferase responsible for adding an a1,6 fucosyl residue to the core region of N-linked oligosaccharides, results in defective midline patterning during zebrafish development. Reduced FucT8 expression leads to mild cyclopia, small forebrains, U-shaped somites, among other midline patterning defects. One of the principal FucT8 substrates was identified as Apolipoprotein B (ApoB), the major scaffold protein that is responsible for assembly and secretion of lipoprotein particles in vertebrates. In Drosophila, lipoprotein particles are thought to facilitate cell signaling by serving as a transport vehicle for lipid-modified cell signaling proteins, such as hedgehog. In this regard, knockdown of ApoB expression in zebrafish embryos leads to similar midline patterning defects as those seen in FucT8 morphant embryos. Furthermore, preliminary studies suggest that ApoB facilitates Sonic hedgehog signaling during zebrafish development, analogous to the function of lipoprotein particles during hedgehog signaling in Drosophila. Developmental Dynamics 239:3380-3390,

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Section: Discussionmentioning

confidence: 99%

Core fucosylation is required for midline patterning during zebrafish development

Seth

Machingo

Fritz

et al. 2010

Developmental Dynamics

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“…In contrast, we achieved remarkable performance by combining the poor solvent addition method and the temperatureincrease method as described herein. By concomitant use of the temperature-increase method, 3) the solvent evaporation rate from the droplets to the dispersion medium was accelerated, and the polymer dissolved in the emulsion was rapidly deposited, forming a rigid outer-shell on the surface of the emulsion. Thereby, the drug and water would remain within the polymer shell.…”

Section: Discussionmentioning

confidence: 99%

“…In a previous study, we illustrated the effect of temperature-increase rate in the solvent evaporation process (referred to as the temperature-increase method hereafter) on the drug release property of the microspheres. 3) In this method, the preparative vessel was heated up at the constant rate in order to evaporate the dispersed solvent. By means of the temperature-increase method, microspheres showing constant drug release were prepared over a short period of time.…”

mentioning

confidence: 99%

Effect of Amount of Water in Dispersed Phase on Drug Release Characteristics of Dextran Microspheres Prepared by Emulsion-Solvent Evaporation Process

Miyazaki

Yakou

Takayama

2007

Biological & Pharmaceutical Bulletin

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The microencapsulation techniques are widely used in the pharmaceutical field.1) Among them, emulsion solvent evaporation method has taken considerable attention in recent years, and numerous methods to manipulate a drug release behavior have been reported.2) Several preparation variables influencing on the properties of microspheres have been identified, including solvent type, solvent removal rate, preparation temperature, composition and viscosity of polymer, and drug loading amount. In a previous study, we illustrated the effect of temperature-increase rate in the solvent evaporation process (referred to as the temperature-increase method hereafter) on the drug release property of the microspheres.3) In this method, the preparative vessel was heated up at the constant rate in order to evaporate the dispersed solvent. By means of the temperature-increase method, microspheres showing constant drug release were prepared over a short period of time. Although a variety of studies has been conducted, the effects of poor solvent in the dispersed phase on the physical properties and drug release characteristics are not well-documented.The aim of the current work was to evaluate the effects of poor solvent in the dispersed phase on drug release from the microspheres when the temperature-increase method was employed for the emulsion solvent evaporation process. In this study, model microspheres were prepared from theophylline (TH) and hydrophobic dextran derivative (PDME). TH was used as a representative drug since sustained-release formulations are desirable because of the short elimination half-life in humans. PDME was selected as a water-insoluble polymer; it is used for contact lenses in the industrial field. Mixtures of acetone and water were used as the dispersed phase and liquid paraffin as the continuous phase. The microspheres were characterized by their size and drug loading efficiency. The morphology of the microspheres was then observed by scanning electron microscopy. In addition, drug release was examined and its kinetics were analyzed. MATERIALS AND METHODSMaterials TH as an anhydrous form was purchased from Sigma Chemical Co. (St. Luis, MO, U.S.A.) and was used after sieving through a 200-mesh sieve (less than 75 mm). PDME was kindly donated by Meito Sangyo Co., Ltd. (Nagoya, Japan) and was used without further purification. PDME is prepared from dextran (Mw 40000) by substitution of 0.58 mol acetyl, 0.81 mol propionyl, 1.42 mol butyryl and 0.16 mol methacryloyl per anhydroglucose unit of dextran. Acetone was purchased from Wako Pure Chemical Industry, Ltd. (Osaka, Japan). Liquid paraffin conforming to JP standard was obtained from Iwaki Seiyaku Co., Ltd. (Tokyo, Japan). Sucrose-ester (DKF-10) was generously supplied by Dai-ichi Kogyo Seiyaku Co., Ltd. (Kyoto, Japan) and was used as an emulsifier. Polyoxyethylene (20) sorbitan monolaurate (Tween 20) was purchased from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). Ultra purified water generated by Direct-Q (Nihon Millipore Ltd., Tokyo, Japan) was ...

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“…Microspheres containing theophylline were prepared by an emulsion solvent evaporation process [8]. The mean diameter increased from 97 to 187 lm as the evaporation rate was decreased from 30 to 7.5°C/h.…”

Section: Microsphere Preparationmentioning

confidence: 99%

Novel Preparation and Properties of Microspheres involving a Hydrocarbon‐Perfluorocarbon Solvent Extraction Process

et al. 2010

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Microspheres were prepared using a hydrocarbon-perfluorocarbon solvent extraction process. The effects of solidification conditions on the properties of the microspheres were investigated. The emulsion flow velocity into the solidification vessel was found to have the greatest effect on the final particle size. Smaller particles were formed when the emulsion flow velocity into the solidification vessel was increased. However, mixing conditions during the solidification and the solidification temperature were also found to greatly affect the particle size of the microspheres. The initial droplet size distribution, created in the emulsification step, changed during the solidification phase, which happened partly because the emulsion stability was poor. Increasing the stirrer speed in the solidification vessel led to the production of smaller particles. At higher temperatures, larger particles were formed due, in part, to the particles forming hollow cores. Solidification conditions also strongly affected the compactness of the particles. More compact particles were produced at 10°C than at higher temperatures, i.e., 50°C and 90°C, where hollow particles were mainly produced. More compact particles were produced at 50°C when toluene was added to the PFC used in the solidification step. This result was attributed to the slower mass transfer of toluene from the solidifying droplets into the continuous phase.

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Effect of temperature-increase rate on drug release characteristics of dextran microspheres prepared by emulsion solvent evaporation process

Cited by 38 publications

References 20 publications

Core fucosylation is required for midline patterning during zebrafish development

Core fucosylation is required for midline patterning during zebrafish development

Effect of Amount of Water in Dispersed Phase on Drug Release Characteristics of Dextran Microspheres Prepared by Emulsion-Solvent Evaporation Process

Novel Preparation and Properties of Microspheres involving a Hydrocarbon‐Perfluorocarbon Solvent Extraction Process

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