Polymeric drug delivery applications

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). 

In this study, we demonstrate new pH/temperature-sensitive polymers with transitions resulting from both polymer-polymer and polymer-water interactions and their applications as stimuli-responsive drug carriers [22-23], For this purpose, copolymers of (Ai,Ai-dimethylamino)ethyl methacrylate (DMAEMA) and ethylacrylamide (EAAm) [or acrylamide (AAm)] were prepared and characterized as polymeric drug delivery systems modulated for pulsatile and time release. 

Another driver for novel polymer research was the increasing complexity of polymeric drug delivery systems. An ideal polymer for these applications should serve the following requirements ... 

Jacob, J.S., et al., Polymeric drug delivery system for hydrophobic drugs, US patent application 20050249799, published on November 10, 2005. 

Drug Delivery Applications and Biological Fate of Natural Polymeric Nanoparticles... 

Interfacial Polymerization Interfacial polymerization is a process whereby very thin films or membranes, on the order of nanometer thickness, are produced by reacting two monomers at the interface between two immiscible solutions [199], Nanoparticles [200] and aqueous core capsules with very thin membranes have been produced using this method for drug delivery applications. 

Obviously, the regulatory status of polyesters means that these materials dominate the field as far as commercial development is concerned. However, there is a myriad assortment of polymers that continue to be developed for drug delivery applications. These efforts are aimed at developing new polymeric materials designed specifically to overcome obstacles in drug... 

Surface or bulk chemical reactions, including erosion and degradation are important aspects of polymeric systems. These processes can be desired, as is the case for surface modification reactions to increase, e.g., biocompatibility or drug delivery applications, while other processes are unwanted, such as ageing, degradation in harsh environments, or erosion. AFM approaches offer a unique possibility to study these processes in many cases under realistic conditions and thereby help identify the underlying mechanisms. 

Lee, P. I. and Good, W. R., Eds. Surface chemical analysis of polymeric drug delivery systems by static secondary ion mass spectrometry (SSIMS) and SIMS imaging. In American Chemical Society Symposium Series Controlled-Release Technology, Pharmaceutical Applications. American Chemical Society, Washington, DC, 1987. 

RESS is useful for materials that are soluble in CO2. Unfortunately, CO2, with no dipole moment and very low polarizability, is a very weak solvent and dissolves very few polymers. Cosolvents such as methanol or acetone can be mixed with SCFs to increase the solvating power of SCFs during RESS. In drug delivery applications, RESS has been used to prepare polymeric films, microparticles, nanospheres, liposomes, and porous foams (Figure 1). A... 

This degradation process is autocatalytic, since the g-hydroxybutyric acid that is produced catalyzes the hydrolysis reaction. To prevent abrupt degradation and erosion, a basic compound must be incorporated into the polymer. For example, sodium bicarbonate can be incorporated into a polymeric device composed of Alzamer to control the rate of polymer degradation and erosion. Although the polymer has been used for a number of drug delivery applications, it is difficult to produce and requires addition of significant amounts of a basic chemical to prevent uncontrolled degradation [21]. 

Swelling is one of the functional properties used to characterize biopolymers required for modified or controlled drug delivery systems. The biopolymers employed for modified drug delivery applications are hydrogels that form three-dimensional polymeric networks when they come into contact with water, they absorb many times their weight of water but they do not dissolve. Swelling of the ceUulosics in different biorelevant media must be established. 

FIGURE 54.23 A schematic representation of inverse miniemulsion or microemulsion polymerization for the preparation of nanometer-sized particles of water-soluble and water-swellable polymers as well as cross-linked particles in the presence of cross-linkers. (Reprinted from Polymer, 50(19), Oh, J.K., Bencherif, S.A., and Matyjaszewski, K., Atom transfer radical polymerization in inverse miniemulsion A versatile route toward preparation and functionalization of microgels/nanogels for targeted drug delivery applications, 4407-4423. Copyright 2009, with permission from Elsevier.)... 

Oh, J.K. Bencherif, S.A. Matyjaszewski, K. Atom transfer radical polymerization in inverse miniemulsion A versatile route toward preparation and funetionalization of microgels/nanogels for targeted drug delivery applications. Polymer 2009,50 (19), 4407-4423. 

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