Biodegradable poly[(amino acid ester)phosphazenes] for biomedical applications

Polyphosphazene derivatives with amino acid ester side groups were prepared by reacting poly(dichlorophosphazene) with ethyl esters of amino acids and were characterizedby H-1, P-31-NMR and DSC analyses. The in vitro rate of degradation of these polymers depended on the nature of the amino acids while introducing small amounts of depsipeptide ester co-substituents increased degradation rates. The rate of hydrolytic degradation of the poly[(organo)phosphazene] materials could be controlled by the amino acid ester by the depsipeptide ester side group content and by blending poly[(amino acid ester)phosphazenes] with poly[(amino acid ester)-co-(depsipeptide ester)phosphazenes]. Poly[(glycine ethyl ester)phosphazenes] prepared from poly[(dichloro)phosphazenes] degradation rates were independent of molecular weight. Degradations of polymer blends indicate that an intramolecular catalysis of the polymer by the pendent carboxylic acid.