A new technique to efficiently entrap leuprolide acetate into microcapsules of polylactic acid or copoly(lactic/glycolic) acid.

Ogawa, Yasuaki; Yamamoto, Masaki; Okada, Hiroaki; Takatsuka, Yuichi; Shimamoto, Tsugio

doi:10.1248/cpb.36.1095

Cited by 473 publications

(159 citation statements)

References 0 publications

Supporting

Mentioning

152

Contrasting

Unclassified

Order By: Relevance

“…Small volume (Li et al, 1999;Schlicher et al, 1997) and high viscosity (Ogawa et al, 1988;Maa and Hsu, 1997) are preferable in achieving high encapsulation efficiency. It is likely that the two factors also contribute to creating stable primary emulsion.…”

Section: Stability Of Primary Emulsionmentioning

confidence: 99%

Control of encapsulation efficiency and initial burst in polymeric microparticle systems

2004

View full text Add to dashboard Cite

Initial burst is one of the major challenges in protein-encapsulated microparticle systems. Since protein release during the initial stage depends mostly on the diffusional escape of the protein, major approaches to prevent the initial burst have focused on efficient encapsulation of the protein within the microparticles. For this reason, control of encapsulation efficiency and the extent of initial burst are based on common formulation parameters. The present article provides a literature review of the formulation parameters that are known to influence the two properties in the emulsion-solvent evaporation/extraction method. Physical and chemical properties of encapsulating polymers, solvent systems, polymer-drug interactions, and properties of the continuous phase are some of the influential variables. Most parameters affect encapsulation efficiency and initial burst by modifying solidification rate of the dispersed phase. In order to prevent many unfavorable events such as pore formation, drug loss, and drug migration that occur while the dispersed phase is in the semi-solid state, it is important to understand and optimize these variables.

show abstract

Section: Stability Of Primary Emulsionmentioning

confidence: 99%

Control of encapsulation efficiency and initial burst in polymeric microparticle systems

2004

View full text Add to dashboard Cite

show abstract

“…19,26,28 The basic formulations were called M1 to M3 depending on the amount of MH in the composition. Additionally, different compositions (formulations designed from M4 to M8) were used to study the influence of the physicochemical changes on the drug entrapment.…”

Section: Preparation Of Phbv Microparticlesmentioning

confidence: 99%

“…15 Some of the commonly reported processes of preparing microparticles from biodegradable polymers include polymer phase separation, solvent evaporation and solvent extraction, supercritical fluid and spray drying techniques. [16][17][18] The double emulsion/solvent evaporation procedure proposed by Ogawa et al 19 represents an easy and reproducible method that provides uniformity of particle size. This technique has been widely used by several research groups to obtain micro and nanoparticles.…”

Section: Introductionmentioning

confidence: 99%

Physicochemical characterization of a hydrophilic model drug-loaded PHBV microparticles obtained by the double emulsion/solvent evaporation technique

Farago¹,

Raffin²,

Pohlmann³

et al. 2008

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

Micropartículas de poli(3-hidroxibutirato-co-3-hidroxivalerato) (PHBV) contendo um fármaco modelo hidrofílico, o cloridrato de metformina (MH), foram obtidas pela técnica de emulsão múltipla/evaporação do solvente. Diversas formulações foram preparadas, com o objetivo de investigar a influência de cada composição sobre a eficiência de encapsulação (EE). O resultado mais elevado de EE (9,76%) foi verificado quando da simultânea alcalinização e adição de NaCl na fase aquosa externa da formulação. O estudo por MEV das micropartículas revelou morfologia esférica e superfície rugosa. As intensidades de difração cristalina para as micropartículas contendo o MH foram menores do que aquelas observadas para a mistura física. Os resultados obtidos por IVTF sugerem que nenhuma ligação química foi formada entre o polímero e o fármaco. A avaliação por análise térmica indica o surgimento de interações favoráveis entre MH e PHBV. O estudo de liberação in vitro demonstrou a influência do PHBV no perfil de dissolução do MH.Poly(3-hydroxybutirate-co-3-hydroxyvalerate) (PHBV) microparticles containing a watersoluble model drug, metformin hydrochloride (MH), were obtained by a double emulsion/solvent evaporation technique. Several formulations were prepared in order to investigate the influence of each composition on the encapsulation efficiency (EE). The highest value of EE (9.76%) was obtained using simultaneously pH alkalinization and NaCl addition in the external water phase of the formulation. SEM study revealed a spherical morphology and a rough surface. The crystalline diffraction intensities for the MH-loaded microparticles were lower than that verified for the physical mixture. FTIR results suggested that no chemical bond between the polymer and the drug was formed. Also thermal analyses indicated a favorable interaction between MH and PHBV. In vitro drug release demonstrated the influence of the PHBV on the dissolution profile of MH. Keywords: PHBV, double emulsion/solvent evaporation technique, hydrophilic model drug, microparticles IntroductionBiodegradable polymeric materials have been received increasing interest due to several ecological and recycling aspects. 1,2 Among numerous microbial polyesters, poly(3-hydroxybutirate-co-3-hydroxyvalerate) (PHBV) has been widely investigated as a biocompatible material suitable for pharmaceutical and medical applications. The literature reports the use of PHBV in tissue engineering and as drug delivery systems. [3][4][5][6][7][8][9][10][11][12] Particularly, PHBV exhibits unique and interesting physicochemical features (e.g. piezoelectricity) in addition to their mechanical properties similar to the polypropylene and other widely used polyesters [e.g. poly(DL-lactide) and poly(DL-lactide-co-glycolide)]. 13 Moreover, PHBV is a less crystalline biopolymer than poly(3-hydroxybutirate), therefore an enhanced degradation rate is observed. 14 Farago et al. 1299 Vol. 19, No. 7, 2008 Several methods have been used to prepare microparticles, for both natural and synthetic polymers. 15...

show abstract

“…The particles were prepared by double emulsion solventevaporation (10,11). The primary water/oil emulsion was made by first dissolving 100 mg of PLGA in 1 ml of methylene chloride, then adding 100 l of Gd-DTPA and 100 l of VEGF.…”

Section: Microsphere Preparationmentioning

confidence: 99%

“…For the Gd-DTPA, 54% was released by day 1, 0.2%/day was released during the slow steady-state phase (days 2-16), and 5%/day was released during the rapid steady-state phase (days 18 -24). For the VEGF, 3% was released by day 1, 0.1%/day was released during the slow steady-state phase (days [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], and 6%/day was released during the rapid steady-state phase (days 24 -35). The release of VEGF slightly lags that of Gd-DTPA.…”

Section: Release Kineticsmentioning

confidence: 99%

In vitro release of vascular endothelial growth factor from gadolinium‐doped biodegradable microspheres

Faranesh

Nastley

Cruz

et al. 2004

Magnetic Resonance in Med

View full text Add to dashboard Cite

A drug delivery vehicle was constructed that could be visualized noninvasively with MRI. The biodegradable polymer poly(DL-lactic-co-glycolic acid) (PLGA) was used to fabricate microspheres containing vascular endothelial growth factor (VEGF) and the MRI contrast agent gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). The microspheres were characterized in terms of size, drug and contrast agent encapsulation, and degradation rate. The PLGA microspheres had a mean diameter of 48 ؎ 18 m. The gadolinium loading was 17 ؎ 3 g/mg polymer and the VEGF loading was 163 ؎ 22 ng/mg polymer. Electron microscopy revealed that the Gd was dispersed throughout the microspheres and it was confirmed that the Gd loading was sufficient to visualize the microspheres under MRI. VEGF and Gd-DTPA were released from the microspheres in vitro over a period of ϳ6 weeks in three phases: a burst, followed by a slow steady-state, then a rapid steady-state. Biodegradable Gd-doped microspheres can be effectively used to deliver drugs in a sustained manner, while being monitored noninvasively with MRI.

show abstract

A new technique to efficiently entrap leuprolide acetate into microcapsules of polylactic acid or copoly(lactic/glycolic) acid.

Cited by 473 publications

References 0 publications

Control of encapsulation efficiency and initial burst in polymeric microparticle systems

Control of encapsulation efficiency and initial burst in polymeric microparticle systems

Physicochemical characterization of a hydrophilic model drug-loaded PHBV microparticles obtained by the double emulsion/solvent evaporation technique

In vitro release of vascular endothelial growth factor from gadolinium‐doped biodegradable microspheres

Contact Info

Product

Resources

About