Polymeric delivery systems applications

Recent development in polymeric delivery systems for the controlled release of therapeutic agents has demonstrated that these systems not only can improve drug stability both in vitro and in vivo by protecting labile drugs from harmful conditions in the body, but also can increase residence time at the application site and enhance the activity duration of short half-life drugs. Therefore, compounds which otherwise would have to be discarded due to stability and bioavailability problems may be rendered useful through a proper choice of polymeric delivery system. 

Prokop A (1997) Micro-particulate and nano-particulate polymeric delivery system. US patent pending, 1997 also PCT application W09918934A1... 

El-Nokaly, M. A., Piatt, D. M., and Charpentier, B. A. (1993), Polymeric Delivery Systems Properties and Applications, ACS Symposium Series, Washington, DC. 

DeLuca, P.P., et al., Biodegradable polyesters for drug and polypeptide delivery, in M.A. El-Nokaly, D.M. Piatt, and B.A. Charpentier. Polymeric Delivery Systems Properties and Applications. Washington, DC American Chemical Society, 1993, pp 53-79,... 

Because these types of polymeric matrix systems are the simplest to design and the easiest to obtain approval by the Food and Drug Administration, they have been the most extensively studied in the past two decades. Numerous polymers have been evaluated for these types of drug delivery systems and although it would be impractical to present each of these polymers and its specific application to drug delivery, this chapter will review in general the types of polymers used as matrices for drug delivery (1-4). 

In addition to solvent uses, esters of lactic acid can be used to recover pure lactic acid via hydrolysis, which in-tum is used to make optically active dilactide and subsequently polylactic acid used for drag delivery system.5 This method of recovery for certain lactic acid applications is critical in synthesis of medicinal grade polymer because only optically active polymers with low Tg are useful for drug delivery systems. Lactic acid esters themselves can also be directly converted into polymers, (Figure 1), although the commercial route proceeds via ring-opening polymerization of dilactide. 

Recent developments in polymer chemistry have allowed for the synthesis of a remarkable range of well-defined block copolymers with a high degree of molecular, compositional, and structural homogeneity. These developments are mainly due to the improvement of known polymerization techniques and their combination. Parallel advancements in characterization methods have been critical for the identification of optimum conditions for the synthesis of such materials. The availability of these well-defined block copolymers will facilitate studies in many fields of polymer physics and will provide the opportunity to better explore structure-property relationships which are of fundamental importance for hi-tech applications, such as high temperature separation membranes, drug delivery systems, photonics, multifunctional sensors, nanoreactors, nanopatterning, memory devices etc. 

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. 

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