Drug delivery applications

The simplest configuration of a controlled release device is where a drug is either dissolved in high concentration or suspended as particles in a monolithic polymer such as a cylindrical polymer fiber. The release of the drug from it may occur via  

Diffusive transfer through the polymer matrix to the surrounding tissue. 

Release of the dissolved or suspended drug due to slow biodegradation or erosion of the surface layers of the fiber. 

Slow release of covalently bonded drug via hydrolytic cleavage of the linkages. 

Expressions for the kinetics of diffusion of solutes through pol5miers have been extensively discussed by Crank (1980). These are derived primarily by assuming that Pick s Law applies the concentration gradient of the drug inside and outside the pol5mier matrix is the driving force for diffusive transfer  

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Ranade, S.V., Richard, R.E., and Hehnus, M.N. Styrenic block copolymers for biomaterial and drug delivery applications, Acta Biomater., 1, 137, 2005. 

For many drug delivery applications, the preferred method of delivery of the dosage form is by injection. For controlled release applications, the most frequently used approach to allow this method of administration is to prepare microspheres of the polymer containing the drug to be delivered. Several different techniques have been developed for the preparation of microspheres from polyanhydrides. 

It was therefore particularly inteipesting to investiage whether it would be possible to replace BPA by various derivatives of L-tyrosine as monomeric building blocks for the synthesis of poly-(iminocarbonates). In order to be practically useful in drug delivery applications, the replacement of BPA by derivatives of tyrosine must give rise to mechanically strong yet fully biocompatible polymers. 

Amphipathic peptides contain amino acid sequences that allow them to adopt membrane active conformations [219]. Usually amphipathic peptides contain a sequence with both hydrophobic amino acids (e.g., isoleucine, valine) and hydrophilic amino acids (e.g., glutamic acid, aspartic acid). These sequences allow the peptide to interact with lipid bilayer. Depending on the peptide sequence these peptides may form a-helix or j6-sheet conformation [219]. They may also interact with different parts of the bilayer. Importantly, these interactions result in a leaky lipid bilayer and, therefore, these features are quite interesting for drug delivery application. Obviously, many of these peptides are toxic due to their strong membrane interactions. 

N. Kossovsky, A. Gelman, E. Sponsler, H. Hnatyszyn 1994, (Surface modified nanocrystalline ceramics for drug delivery application), Biomaterials 15, 1201. 

Biodegradable polyurethanes have been proposed and studied before (9-72). The difference in our study is the inclusion of a phosphoester linkage instead of the commonly used polyester component. This seems to provide more flexibility as the side chain of the phosphate or phosphonate can be varied. For controlled drug delivery applications, drugs can be linked to this site to form a pendant delivery system. Moreover, for certain medical applications, fast degradation rate is obtainable by the introduction of these hydrolyzable phosphoester bonds. With the LDI based polyurethanes, drugs or other compounds of interest can also be coupled to the ester side chain of the lysine portion. 

Another class of environmentally sensitive materials that are being targeted for use in drug delivery applications is thermally sensitive polymers. This type of hydrogel exhibits temperature-sensitive swelling behavior... 

Poly(2-hydroxyethyl methacrylate) (PHEMA) has been the most widely used polymer in drug delivery applications. It is an extremely hydrophilic... 

In the last few years there have been new creative methods of preparation of novel hydrophilic polymers and hydrogels that may represent the future in drug delivery applications. The focus in these studies has been the development of polymeric structures with precise molecular architectures. Stupp et al. (1997) synthesized self-assembled triblock copolymer, nanostructures that may have very promising applications in controlled drug delivery. Novel biodegradable polymers, such as polyrotaxanes, have been developed that have particularly exciting molecular assemblies for drug delivery (Ooya and Yui, 1997). 

Bioerodible polymers offer a unique combination of properties that can be tailored to suit nearly any controlled drug delivery application. By far the most common bioerodible polymers employed for biomedical applications are polyesters and polyethers (e.g., polyethylene glycol), polylactide, polyglycolide and their copolymers). These polymers are biocompatible, have good mechanical properties, and have been used in... 

We have already mentioned a few of the polyanhydride chemistries that have been studied in drug delivery applications. Tables II through VII present some of the polyanhydrides that have been explored for drug... 

It is important to characterize the thermal properties of polyanhydrides that are proposed for drug delivery applications, as changes in crystallinity... 

Forbes B, Ehrhardt C (2005) Human respiratory epithelial cell culture for drug delivery applications. Eur J Pharm Biopharm 60(2) 193-205. 

Fenske DB, Maurer N, Cullis PR. Encapsulation of weakly-basic drugs, anti-sense oligonucleotides and plasmid DNA within large unilamellar vesicles for drug delivery applications. In Torchilin VP, Weissig V, eds. Liposomes A Practical Approach. 2nd ed. Oxford Oxford University Press, 2002, Chapter 6. 

A.L. Klibanov, Microbubble contrast agents Targeted ultrasound imaging and ultra-sound-assisted drug-delivery applications. Invest. Radiol. 41 (2005) 354-362. 

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