Micro drug-delivery system

FIGURE 20-7 A micro drug-delivery system smaller than a penny can dispense medicine to a patient. 

Xylans from beech wood, corncobs, and the alkaline steeping liquor of the viscose process have been shown to be applicable as pharmaceutical auxiliaries [3]. Micro- and nanoparticles were prepared by a coacervation method from xylan isolated from corncobs [150]. The process is based on neutralization of an alkaline solution in the presence of surfactant, which was shown to influence both the particle size and morphology. They are aimed at applications in drug delivery systems. 

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... 

C. T. Rhodes, Determination of micro-pH in solid drug delivery systems, Drug Dev. Indust. Pharm, 25, 1221... 

The variety of materials which can be incorporated into polyelectrolyte multilayers makes them attractive to use as biosensors [431], Polyelectrolyte multilayers can also be formed on curved surfaces of small particles [432], After adsorption, the core particle can be chemically dissolved and a hollow polyelectrolyte capsule remains. These capsules are selectively permeable for small molecules like water or certain dyes. The permeability can be tuned externally by varying the ion strength, pH, temperature and solvent nature [433 135], Therefore, it has been suggested to use them as selective membranes for separation, as well as a possible drug delivery system. The adjustment of their size and permeability allows us to exploit them as micro- or nanocontainers for chemical synthesis and crystallization. 

Micro- and nanoparticulate drug delivery systems as well as delivery systems based on liposomes are described in detail in Chapters 9 and 10. Besides other advantages which are discussed in the mentioned chapters, these formulations are capable of protecting incorporated drugs from enzymatic degradation. 

Fig. 23 Schematic illustration of a pH-activated drug-delivery system and the pH-dependent formation of micro-porous membrane in the intestinal tract.

Alternative means that help overcome these nasal barriers are currently in development. Absorption enhancers such as phospholipids and surfactants are constantly used, but care must be taken in relation to their concentration. Drug delivery systems, including liposomes, cyclodextrins, and micro- and nanoparticles are being investigated to increase the bioavailability of drugs delivered intranasally [2]. 

Investigations into the possibilities for the formulation of the drug substance as a more complex drug delivery system such as an emulsion, liposomal, micro- or nanoparticle, or other colloidal product. 

TABLE 39.10 Micro- and Nano Drug Delivery Systems... 

Kompella UB, Koushik K. Preparation of drug delivery systems using supercritical fluid technology. Crit Rev Ther Drug 2001 18 173-199. Reverchon E. Supercritical antisolvent precipitation of micro- and nanoparticles. J Supercrit Fluid 1999 15 1-21. 

Figure 3. Microfluidic Device. (A) Time lapse illustrating repulsion the ejection of 1.9 pm fluorescent polystyrene microsphere particles from an electroactive microwell. After dissolution of the membrane, the fluorescent particles can be seen in the well. White hnes outline the gold electrodes features. Images are taken every 2 s (total of 10 s). (B) Schematic of the electroactive microwell drug delivery system developed here. Scale bar represents 2 mm. (C) Micro fluidic device with electrical leads connected to thin copper wires. Inset Magnified view of microchip from above looking at the region near the membrane. (D) To illustrate the electrokinetic transport processes involved in the ejection stage, a finite element analysis of time-dependent species transport of the system is shown. Images show cut view of species concentration every 60 s up to 300 s after the ejection process.

Maeda M, Tani S, Sano A, Eujioka K Micro-stmcture and release characteristics of the minipellet, a collagen-based drug delivery system for controlled release of protein dmgs,... 

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