Microcapsules spherical-surfaced

A large variety of drug delivery systems are described in the literature, such as liposomes (Torchilin, 2006), micro and nanoparticles (Kumar, 2000), polymeric micelles (Torchilin, 2006), nanocrystals (Muller et al., 2011), among others. Microparticles are usually classified as microcapsules or microspheres (Figure 8). Microspheres are matrix spherical microparticles where the drug may be located on the surface or dissolved into the matrix. Microcapsules are characterized as spherical particles more than Ipm containing a core substance (aqueous or lipid), normally lipid, and are used to deliver poor soluble molecules... 

The appearance of the individual microcapsules is shown in Fig. 1. Most individual microcapsules are approximately spherical and show a surface made up of deposited plates of poly(DL-lactic acid) in which the drug is embedded. Many of the larger microcapsules are cemented together by further plates of poly(DL-lactic acid). The effect of compression on these microcapsules is shown in Fig. 2. At a compressive force of 2 kN (Fig. 2(a)) the electron micrograph of the tablet fracture surface shows that the microcapsules, while distorted, remain essentially intact and rounded, with a relatively open porous structure to the tablet as a whole. At 10 kN force (Fig. 2(b)) the microcapsules at the fracture are flattened, cracked and distorted so that the fracture surface shows a far less open, porous aspect. Both of these microcap tablets have a very different appearance from that produced by the simple mixture (Fig. 3), where the individual plates of poly(DL-lactic acid) are mixed with the drug crystals in an open structure from which release would be easily... 

The outer shape of the microcapsules depends on the type of material in the core and the method of depositing the wall material. Microcapsules may be smooth, spherical particles and grape-like conglomerates or irregular particulates with smooth or rough surfaces. 

EC microcapsules containing Rosemary oil or limonene were obtained by phase separation method. According to this procedure, EC microcapsules without oil could also be produced. This could be explained due to EC inter cial activity, which stabilizes the formed emulsion. Surfactant-fiee multiple emulsions using EC as a polymeric emulsifier have already been reported by Melzer and collaborators [8]. From the scanning electron micrographs shown in Fig. 1 it is observed that EC microc g)sules had regular spherical sh, the size of microcapsules varied and that the surface was porous. 

Coating thickness is sometimes difficult to measure conveniently due to the fine size of some powders and to the unevenness of the surface of some granular materials. A reasonably estimate of the coating thickness for spherical microcapsules can be calculated using the following expression (Dewettinck, 1977) ... 

Scanning Electron Microscopy - Silica microcapsules are studied by ESEM. The spherical particles have average diameters ranging from 1-30 pm, shown in - Figure 15. The shells of microparticles present a smooth surface. 

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