Some applications of polymeric systems in drug delivery

Ethyl acrylate 2-Ethylhexyl acrylate Isooctyl acrylate 

Different film coats applied to tablet surfaces can lead to quite different rates of solution. 

Pressure-sensitive silicone adhesives are formed from the most highly crosslinked 

Other pressure-sensitive adhesives used in transdermal delivery device include those shown in Table 8.f f. 

6 Some applications of polymeric systems in drug delivery 

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Some applications of polypyrrole, such as drug delivery devices, require specific ion transport. Control of the ion transport process requires determination of the identity of the mobile ion, which is complicate by the fact that there are several ions present in the system. Moreover, Shimidzu and co-woiicers [138,139] demonstrated that ion transport in polypyrrole can be modified by the use of polymeric anions as dopants. Miller and Zhou [140] proved that the electrochemical switching of polypyrrole could achieve controlled release of small anions (such as CIO4), while the incorporation of an immobile polyanion (such as polystyrene sulfonate) resulted in cation transport. The polyanions become trapped within the polypyrrole matrix due to their large size and, perhaps more important, their entanglement with the polypyrrole chains. This increases the stability and mechanical strength of polypyrrole and improves electrical conductivity and electroactivity [141,142]. Therefore it has been of significant interest in the polymerization of pyrrole in polyanion electrolyte solutions [143,144]. 

Among the many classes of polymeric materials now available for use as biomaterials, non-degradable, hydrophobic polymers are the most widely used. Silicone, polyethylene, polyurethanes, PMMA, and EVAc account for the majority of polymeric materials currently used in clinical applications. Consider, for example, the medical applications listed in Table A.l most of these applications require a polymer that does not change substantially during the period of use. This chapter describes some of the most commonly used non-degradable polymers that are used as biomaterials, with an emphasis on their use in drug delivery systems. 

Some new trends can be recognized in the points such as the interaction of short-lived active species in some spatial distributions measured by spin echo and pulse radiolysis methods. The application of polymers for drug-delivery systems is here discussed with reference to low temperature radiation polymerization techniques. Ion beam irradiation of polymers is also reviewed for which further research is becoming important and attractive for so-called LET effects and high density excitation problems. In the applied fields the durable polymers used in strong and dense irradiation environments at extremely low temperature are here surveyed in connection with their use in nuclear fusion facilities. 

Surfactant aggregates (microemulsions, micelles, monolayers, vesicles, and liquid crystals) are recently the subject of extensive basic and applied research, because of their inherently interesting chemistry, as well as their diverse technical applications in such fields as petroleum, agriculture, pharmaceuticals, and detergents. Some of the important systems which these aggregates may model are enzyme catalysis, membrane transport, and drug delivery. More practical uses for them are enhanced tertiary oil recovery, emulsion polymerization, and solubilization and detoxification of pesticides and other toxic organic chemicals. 

Another remarkable feature of responsive polymeric systems is that interactions on the molecular scale (the stimulus of some sort) lead to macroscopically detectable changes that are finally employed for the function (e.g., directed delivery of drugs). As the molecular-scale interactions and macroscopic function are so intimately linked it is noteworthy that rather few studies have dealt with the nanoscopic level of these materials. This may be due to the fact that many conventional methods of physical polymer characterization may simply not be able to resolve the many different, often counteracting interactions [18, 49, 50]. In processes like a response of any kind, solvent-polymer, solvent-solvent, and polymer-polymer interactions all play a cmcial role. Better understanding of the structure and interactions on the nanoscale is not only of value in itself but it may also shed light on similar processes in biomacromolecules and may aid the design and control of responsive polymers with respect to their applications [8, 48, 49]. These applications can be counted to the above-mentioned societal need of health, as responsive polymers are hot candidates for, e.g., drug or nucleic acid delivery purposes. 

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