Novel biodegradable polyphosphazenes containing glycine ethyl ester and benzyl ester of amino acethydroxamic acid as cosubstituents

Novel biodegradable polyphosphazenes containing glycine ethyl ester and benzyl ester of amino acethydroxamic acid as cosubstituents (PGBP) were synthesized by further modifying poly[bis(glycine ethyl ester)phosphazene] (PGP). The polymers were characterized by IR, 1H-NMR, DSC, and elemental analysis. Degradation experiments were conducted in vitro at varied pH conditions. The results indicated that the degradation of PGBP was pH-sensitive. The sample dissoluted after 1.5 days under a physiological condition (pH 7.4) but took more than 20 days under an acidic condition (pH 5–6), which was related to the content of the benzyl ester of amino acethydroxamic acid in the polymer. The “two-stage” degradation mechanism of PGBP was proposed: that the polymer first degraded to a water-soluble polymeric product with the fast break of side groups, followed by the relatively slow scission of the backbone. This property of PGBP may be useful in controlled drug-delivery systems.