Polymeric drug delivery systems micelles

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... 

In many cases in drug development, the solubility of some leads is extremely low. Fast dissolution rate of many drug delivery systems, for example, particle size reduction, may not be translated into good Gl absorption. The oral absorption of these molecules is usually limited by solubility (VWIImann et al., 2004). In the case of solubility limited absorption, creating supersaturation in the Gl Luids for this type of insoluble drugs is very critical as supersaturation may provide great improvement of oral absorption (Tanno et al., 2004 Shanker, 2005). The techniques to create the so-called supersaturation in the Gl Luids may include microemulsions, emulsions, liposomes, complexations, polymeric micelles, and conventional micelles, which can be found in some chapters in the book. 

Yan H, Tsujii K (2005) Potendal applicadon of poly(N-isopro-pylacrylamide) gel containing polymeric micelles to drug delivery systems. Colloids Surf B Biointerfaces 46 142—146. 

Polymeric micelles are called the new generation of colloid drug delivery systems [28]. In an aqueous medium, block and random copolymers associate into micelles with a structure similar to that of surfactants. Active substances which are insoluble or poorly soluble in water can be built into the lipophilic part of the micelle in two ways i) with dialysis and ii) with the emulsion method (see Figure 18.4). 

The fifth advantage is separated functionality. Polymeric micelles are composed of two phases inner core and outer shell. Various functions required for drug delivery systems can be shared by these structurally separated phases. Each phase can play different roles in drug delivery. As shown in... 

Nasongkla N, Bey E, Ren J, Ai H, Khemtong C, Guthi JS, Chin SF, Sherry AD, Boothman DA, Gao J. 2006. Multifunctional polymeric micelles as cancer targeted, MRI ultra sensitive drug delivery systems. Nano Lett 6 2427 2430. 

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