Controlled release drug delivery systems particles

Chitosan was also formulated in a controlled-release protein delivery system using bovine serum albumin (BSA) as a model drug. Chitosan was reacted with sodium alginate in the presence of tripolyphosphate for bead formation [94]. Parenteral administration of proteins/peptides requires repeated injections because of their extremely short biological half-life. Daily multiple injections are highly risky and require close medical supervision. On this basis, bovine serum albumin (BSA)-loaded chitosan microspheres were prepared to test the drug release behavior in buffers with different pH values. BSA-chitosan microspheres with particle sizes in the range from 5 to 10 pm... 

Zimmer, A. K., Zerbe, H., and Kreuter, J. (1994), Evaluation of pilocarpine-loaded albumin particles as drug delivery systems for controlled delivery in the eye I. In vitro and in vivo characterisation, /. Controlled Release, 32(1), 57-70. 

Fig. 27.5. Mesoporous silica nanoparticles as novel drug delivery systems, (a) Cocondensation method to form functionalized mesoporous silica structures in a surfactant template synthesis, (b) TEM image of mesoporous silica nanoparticles and sketch of a novel drug delivery particle which contains functionalized pores, closed by a gate, and is decorated with ligands for cell targeting, (c) Cell targeting by ligand-receptor interaction at the cell membrane, endosomal uptake and controlled release after pH change from early to late endosome...

Figure 2.3 IgG levels after administration of drug delivery systems in rats. Controlled-delivery systems for antibody class IgG. The insert figures show the release of antibody from the delivery system during incubation in buffered saline. The panel (a) inset shows release from poly(lactic acid) microspheres these spherical particles were 10-100/rm in diameter. The panel (b) inset shows release from a poly[ethylene-co-(vinyl acetate)] matrix these disk-shaped matrices were 1 cm in diameter and 1 mm thick. In both cases, molecules of IgG were dispersed throughout the solid polymer phase. Although the amount of IgG released during the initial 1-2 days is greater for the matrix, the delivery systems have released comparable amounts after day 5. (a) Comparison of plasma IgG levels after direct injection of IgG (open circles) or subcutaneous injection of the IgG-releasing polymeric microspheres characterized in the inset (filled circles). The delivery system produces sustained IgG concentrations in the blood [3]. (b) Comparison of plasma IgG levels after direct intracranial injection of IgG (open squares) or implantation of an IgG-releasing matrix (filled squares) [4]. The influence of the delivery is less dramatic in this situation, probably because the rate of IgG movement from the brain into the plasma controls the kinetics of the overall process.

Both natural and synthetic polymers are widely used in drug dehvery systems. Polymers have inherent flexibility in that they can be synthesized and modified to provide versatile properties to meet the desired controlled drug release profile and biocompatibility. Material performance is highly linked to strength [1], porosity [2], particle size [3], amor-phousity [4], biocompatibility [5], and dissolution properties [6], etc. In order to understand, predict, and improve the performance of polymeric drug delivery systems, various characterization techniques are required, and these are detailed in the following sections of this chapter. 

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