BIODEGRADABLE POLYPHOSPHAZENES FOR DRUG-DELIVERY

Polyphosphazene derivatives having amino acid ester side groups were p repared by reaction of poly(dichlorophosphazene) with ethyl esters of amino acids. The in vitro degradation studies demonstrated that the ra te of degradation depends on the nature of the amino acids. Introducin g small amounts of hydrolytically sensitive groups such as depsipeptid e ester or hydrolysis-catalysing moieties, such as histidine ethyl est er co-substituents, resulted in an increase of the degradation. The ra te of hydrolytic degradation of the polyphosphazene material could be controlled by the content of the hydrolytically sensitive side groups or by blending hydrolysis-sensitive polymers with more stable derivati ves. The results obtained from the in vivo implantation of biodegradab le polyphosphazenes in mice indicate that the materials are very well tolerated by the animal body. Biodegradable polyphosphazenes have been used as matrix for the design of drug delivery systems. The rate of t he in vitro release of mitomycin C from biodegradable polyphosphazenes can be controlled by changing the chemical composition of the polymer or by blending polymers of different chemical compositions.