Emulsification-evaporation processes preparation

J. Jaiswal, S. K. Gupta and J. Kreuter, (2004). Preparation of biodegradable cyclosporine nanoparticles by high-pressure emulsification-solvent evaporation process. J. Control Release, 96(1), 169-178. 

One of the major drawbacks of liposomes is related to their preparation methods [3,4]. Liposomes for topical delivery are prepared by the same classic methods widely described in the literature for preparation of these vesicles. The majority of the liposome preparation methods are complicated multistep processes. These methods include hydration of a dry lipid film, emulsification, reverse phase evaporation, freeze thaw processes, and solvent injection. Liposome preparation is followed by homogenization and separation of unentrapped drug by centrifugation, gel filtration, or dialysis. These techniques suffer from one or more drawbacks such as the use of solvents (sometimes pharmaceutically unacceptable), an additional sizing process to control the size distribution of final products (sonication, extrusion), multiple-step entrapment procedure for preparing drug-containing liposomes, and the need for special equipment. 

Core-sheath nanofibers of PEG-PLA and PEG can be prepared by electrospinning a water-in-oil emulsion in which the aqueous phase consists of a PEO solution in water and the oily phase is a chloroform solution of an amphiphilic PEG-PLLA diblock copolymer. The fibers obtained are composed of a PEO core and a PEG-PLA sheath with a sharp boundary in between. By adjusting the emulsion composition and the emulsification parameters the overall fiber size and the relative diameters of the core and the sheath can be changed. As shown in Fig. 5.15, a mechanism is proposed to explain the process of transformation fi-om the emulsion to the core-sheath fibers, i.e., the stretching and evaporation induced de-emulsification. In principle, this process can be applied to other systems to... 

Liu R, Ma GH, Wan YH, Su ZG. 2005a. Influence of process parameters on the size distribution of PLA microcapsules prepared by combining membrane emulsification technique and double emulsion-solvent evaporation method. Colloids Surf B 45 144-153. 

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