Poly , degradation profiles

Recently, Brich and coworkers (40) reported the synthesis of lactide/glycolide polymers branched with different polyols. Polyvinyl-alcohol and dextran acetate were used to afford polymers exhibiting degradation profiles significantly different from that of linear poly-lactides. The biphasic release profile often observed with the linear polyesters was smoothened somewhat to a monophasic profile. Further, the overall degradation rate is accelerated. It was speculated that these polymers can potentially afford more uniform drug release kinetics. This potential has not yet been fully demonstrated. 

The in vitro degradation profiles of several TDI poly(phosphoester-ure thanes) are shown in Figure 2. It is not possible from this study to correlate the decomposition kinetics with the chemical structure, except for the fact that biodegradability is demonstrated. The in vitro release of 5-FU from PPU-7 is shown in Figure 3. After an initial burst, a reasonably steady and sustained release followed. The UV spectrum of the released 5-FU was identical to that of pure 5-FU, suggesting the chemical integrity of the drug. 

Fig. 5 Degradation profiles (percent weight loss) of compression-molded poly[bis(p-carboxyphenoxy) propane anhydride] (PCPP) containing varying ratios of sebacic acid (SA). The copolymers were incubated in 0.1 M pH 7.4 phosphate buffer at 3TC. (From Ref. l)...

Fig. 5. Degradation profiles of compression molded poly(bis(p-carboxyphenoxy)propane anhydride] and its copolymer with sebacic acid in 0.1 M pH phosphate buffer at 37°C [from Leong, K. W., Brott, B. C., and Langer. R., J. Biomed. Mater. Res. (25). Copyright 1985 John Wiley Sons, Inc. Reprinted by permission of John Wiley Sons).

Besides the common polyhydroxybutyrate (PHB), other polymers of this class are produced by a variety of organisms such as poly-4-hydroxybutyrate, PHV, and polyhy-droxyhexanoate. PHV is a naturally occurring bacterial polyester, which was first isolated by Wallen and coworkers [172,173]. Also, PHV/PHB copolymers have been studied to make a wide range of thermally processable polyesters, which exhibit the necessary long-term degradation profile required for a degradable fracture fixation device [174]. 

Figure 7 Introducing branching into photopolymerizable poly(p-amino esters) has a dose-response effect on several physical properties of the resulting polymer, while maintaining polymerization kinetics and degradation profiles. The molar ratio of acrylates to amines was maintained at 2.4 1.

Figure 2.5 Degradation profiles for the water-soluble PYRP (polymer 1) and PCPP (polymer 4). PYRP poly[ 2s(2-(2-oxo-l-pyrrolidinyl)ethoxy phosphazene]. Combinations of the two side groups produce polymers 2 and 3 with intermediate degradation rates. Conditions pH 7.4 at 55 °C. Reproduced with permission from A.K. Andrianov, A. Marin and P. Peterson, Macromolecules, 2005, 38,19, 7972. 2005, American Chemical Society [41]...

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