Polyanhydrides, linear

As in the alkaline phosphatase example above, p-galactosidase, an enzyme with a molecular weight of approximately 360,000, has also been incorporated into a polyanhydride and released in a well-controlled fashion. As is shown in Fig. 14, the release of 3-galactosidase was quite linear over most of the time examined, and was complete, reaching 100% release in about 800 hr. This experiment utilized 5% loaded, compression-molded wafers of PCPP-SA 9 91, 1.4 cm in diameter and 0.5 mm thick, weighing 50 mg. 

Sanders et al. (1999) attempted to lower the melting points of aromatic polyanhydrides by substituting branched alkyl groups in place of the linear alkyls of P(CPP-SA). They synthesized poly[l,2-bis(/ -carboxyphenoxy)-propane-co-sebacic acid] (P(1,2-CPP-SA)), poly[l,3-bis(/ -carboxyphenoxy)-2-methyl propane-co-sebacic anhydride] (P(CPMP-SA)), and poly[l,3-bis (/ -carboxyphenoxy)-2,2-dimethyl propane-co-sebacic anhydride] (P(CPDP SA)), all of which had melting points below 165°C. 

Femer sind eine Reihe hochmolekularer Stoffe, wie manche Polyanhydride (HS), Polystilbene (D1), Polyphenylene (M3) oder Poly-tetrafluorathylen (H2), teilweise schon von relativ niedrigen Poly-merisat ionsgraden an, in alien Losungsmitteln unloslich, obwohl sie linear aufgebaut sind. 

The degradation rates for a number of polyanhydrides are available in the literature [1, 82,83], However, recently, a new class of polyanhydrides poly(FAD-SA) have been synthesized from non-linear hydrophobic dimer of oleic acid or erucic acid and relatively hydrophilic sebacic acid. This copolymer can be prepared in various ratios of the monomers to achieve the desired degree of hydrophobicity increasing the percentage of FAD, a more hydrophobic copolymer, is obtained. Another advantage of this copolymer is its ability to be formulated as films, microspheres, and beads [84],... 

Linear polyesters of lactides andglycolides, polyfalkyl cyanoacrylates), polyanhydrides, and poly-phosphazenes are some of the polymers commonly used in the development of polymeric particles. 

The linear condensation ou-polyesters, polyanhydrides described in the proceeding papers are easily drawn out into very strong, pliable highly oriented fibers which closely simulate natural silk and cellulose fibers... [1, p. 1587]. 

Proper design calls for a polymer that will degrade by surface erosion much as a bar of soap wears away. Unfortunately, most polymers decompose by penetration of solvent into the interior of a wafer, resulting in bulk erosion. Also, the rate should be linear and predictable. The polyanhydrides form a class that degrades by hydrolysis and that can be tailored accurately to rigid specifications. For the BCNU delivery system, Langer and his collaborators chose a polyanhydride copolymer (20 80) of l,3-bis(p-carboxyphenoxy)propane sebacic acid (CPP SA). 

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