Drug delivery systems micelles

FIGURE 10.3 Schematic presentation of lipid based drug delivery systems. Micelles (right) are composed of a solid lipid core with the polar heads exposed to the aqueous environment. Liposomes (left) are particles with a hpid bilayer surrounding an aqueous core. Drug can be encapsulated in the hydrophobic regions of the lipid particle, in the aqueous environment of the liposome, or adsorbed to the surface of the lipid particle. 

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... 

Solubilization of vinylpyrrolidone, acrylic acid, and A,A -methylene-bis-acrylamide in AOT-reversed micelles allowed the synthesis in situ of a cross-linked polymer with narrow size distribution confined in the micellar domain. These particles displayed high entrapment efficiency of small hydrophilic drugs and have been considered interesting drug delivery systems [239],... 

Recently, biodegradable polymers have been used to fabricate macro- and nanometer scale self-assembled systems such as microspheres (MSs), nanospheres (NSs), polymer micelles, nanogels, and polymersomes (Fig. 1). These have attracted growing interest because of their potential utility for drug delivery systems (DDS), tissue engineering, and other applications. To construct these self-assembled systems... 

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. 

In order to design and facilitate a reversibly temperature-responsive micelle fora drug delivery system, Chung et al. (1997, 1999) and Cammas et al. (1997) conducted extensive research on the... 

Block Copolymers are macromolecules which are composed of blocks usually in linear as it shown in Fig. 3.20, where it is illustrated a classical block copolymer. Main block copolymers are amphiphilic block copolymers having united hydrophilic blocks to hydrophobic blocks. Amphiphilic block copolymer have surfactant properties and form different kinds of associations, such as micelles, nanospheres, nanocapsules and polymersomes This tipe of association can act like excellent vehicles of several active principles. The composition, aggregate formation and the different applications of these materials have been reviewed [112], Figure 3.20 also illustrates the nanoparticulate drug delivery systems formed by amphiphilic block copolymers and their general characteristics. 

The spherical self-assembly in aqueous solution originates from the mushroom shape of the molecule. Moreover, when hydrophobic molecules are present, the micelle includes them as guest molecules, acting as a molecular capsule. As selective adsorption of Pcs to cancer cells has been used as a tool for PDT, these micelles hold potential as drug delivery systems. 

Mtiller-Goymann, C. C. (2004), Physicochemical characterization of colloidal drug delivery systems such as reverse micelles, vesicles, liquid crystals and nanoparticles for topical administration, Eur. J. Pharm. Biopharm., 58(2), 343-356. 

Hagan, S. A., et ai. (1996), Polylactide-poly(ethylene glycol) copolymers as drug delivery systems. 1. characterization of water dispersible micelle-forming systems, Langmuir, 12(9), 2153-2161. 

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. 

Nishiyama, N. Kato, Y. Sugiyama, Y. Kataoka, K. Cisplatin-loaded polymer-metal complex micelle with time-modulated decaying property as a novel drug delivery system. Pharm. Res. 2001, 18, 1035-1041. 

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