Preparation of Poly(D,L-lactide) and Copoly(lactide-glycolide) Microspheres of Uniform Size

Abstract

In an attempt to prepare monodisperse poly(D,L-lactide) and copoly(lactide-glycolide) microspheres, a novel emulsification technique (membrane emulsification) was employed and the preparation conditions which might affect the monodispersity were evaluated. With this technique nearly monodisperse poly(D,L-lactide) and copoly(lactide-glycolide) microspheres were successfully prepared and their sizes were controllable only by making use of microporous glass membranes of different pore sizes. However, in the present system of emulsion (methylene chloride/water) the surfactant used was limited to ionic ones and the amount of polymers available for the formation of microspheres was inevitably too small in concentration to entrap sufficient amounts of drug. As for the drug release, the effect of particle size was not appreciable but the method of solvent removal gave a great influence; the solvent extraction method showed a more drug-sustaining effect than did the solvent evaporation method. The present results suggest the possibility of making drug-loaded and biodegradable monodisperse microspheres.

Size Dependence of Polymer Composition in the Surface Layer of Poly(acrylamide-co-acrylic acid) Hydrogel Microspheres

“…This should be unexpected because the mobility is independent of the particle size, if the particle size is much larger coefficient of the surface layer, e r is the relative permittivity of the solution, e 0 is the permittivity of a vacuum, C DON is than Debye length, 1/k (k is given later in Eq. [8]). The electrophoretic mobility of sample 1 (the smallest size) (see the Donnan potential of the surface layer, C 0 is the potential at the boundary between the surface layer and the sur- Table 2) changes from 02.6 to 01.5 (mm s 01 V 01 cm) in the solutions with the ionic strengths between 0.005 and rounding solution, and k is the Debye-Hückel parameter.…”

Recent developments in manufacturing emulsions and particulate products using membranes

“…After the uniform droplets were prepared, the volatile solvent such as methylene chloride, chloroform, toluene, etc was evaporated. This technique has been applied to manufacture polylactide (PLA) and poly(lactide-co-glycolide) (PLGA) biodegradable microspheres [65,128], polystyrene-poly(methyl methacrylate) (PSt-PMMA) composite microspheres [63,64], and polymer microcapsules containing magnetite (Fe 3 O 4 ) [68] or TiO 2 [66] (Table 9). Also, uniform PUU particles were prepared by solvent evaporation from PUU-xylene droplets after the PU pre-polymer underwent a chain-extending reaction at room temperature with a diamine reagent (Pz) [62].…”

Production of monodisperse water-in-oil emulsions consisting of highly uniform droplets using asymmetric straight-through microchannel arrays

“…The use of monodisperse emulsions consisting of uniformly sized droplets can improve stability against droplet coalescence, and enables the simplified interpretation of experiment results and the precise control of many emulsion properties (Mason et al 1996;McClements 2004). Monodisperse W/O emulsions have high-tech applications such as monodisperse microparticles for column chromatography (Nakashima et al 2000;Hatate et al 1995;Maciejewska and Osypiuk 2005) and monodisperse multiple emulsions, microparticles, and microcapsules as drug delivery carriers (Nakashima et al 2000;Shiga et al 1996;Nagashima et al 1998;Wang et al 2005;Chu et al 2001). W/O emulsions are usually produced using mixers, colloid mills, high-pressure homogenizers, and ultrasonic homogenizers, which apply high shear and extensional stresses to break up droplets into smaller ones (McClements 2004).…”