Polymers, biodegradable selection

It was our intention in formulating this book to take selected polymers that have been widely studied and provide a comprehensive review of their properties, synthesis, and formulations. We hope that this will be useful to individuals who have been in the field for a long time and who would like to have all the information together in one place, as well as to individuals who are new to the field and would like to understand more about the various properties of biodegradable polymers. 

Table 5.13 Selected Mechanical Properties of Some Biodegradable Polymers...

The chapters are selected from the papers presented at two Pharmaceutical Technology Conferences Monte Carlo in 1989 and Veldhoven, The Netherlands, in 1990 and reflect the current state of the art. Chapters 1-8 deal with matrix systems and 9 to 11 with multiparticulate formulations. Chapters 12, 13 and 14 examine opportunities with biodegradable polymers. While the oral route remains the major application, topical (Chapter 8), ophthalmics (Chapters 15-16) and implants (Chapters 16 and 17) are also discussed. 

An 1H-NMR method to determine the fcdecay of selected biodegradable polymers was developed by Benz et al. (2). In this experiment the biodegradable polyketal formed using 5,6-epoxy-2-one-hexane and having an Mn of 13,350 Da was hydrolyzed at 25°C for 16 hours using formic acid in dg-THF (tetrahydrofuran) while collecting spectra at 60 minutes/spectrum. 

Selected examples of therapeutic peptide and protein including vaccines which have been encapsulated into biodegradable polymer-based microspheres are discussed in this section. Besides what is mentioned below, many other proteins and vaccines have been encapsulated in biodegradable polymers, so a glimpse of ongoing... 

As discussed above, enzymes have been used to synthesize biodegradable polymers. Russell and co-workers demonstrated that the molecular weight and polydis-persity of polyesters synthesized by lipases in supercritical solvents can be controlled by selecting the fluid s density, which in turn is controlled by pressure and temperature.The fluid density dictates the solubility of polymer hence, upon reaching a critical size, polymers precipitate from solution. 

A number of reviews cover what has been achieved over the past 20 years in the field of soluble polymers as potential drug carriers.The polymers selected for preparing macromolecular prodrugs can be categorized according to (1) the chemical nature (vinylic or acrylic polymers, polysaccharides, poly(a-amino acids)) (2) the back bone stability (biodegradable polymers, stable polymers) (3) the origin (natural polymers, synthetic polymers) and (4) the... 

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