Synthesis, characterization, in vitro degradation and cytotoxicity of polyphosphazenes containing N-ethoxypyrrolidone side groups

A new biodegradable polyphosphazene (PYRMP) containing N-ethoxypyrrolidone and methoxyethoxyethoxy side groups was synthesized via a route of macromolecular substitution. The synthetic method of poly [bis[2-(2-oxo-1-pyrrolidinyl)ethoxy]phosphazene] (PYRP) was improved. The thermal properties of the polymers were investigated using differential scanning calorimetry. Degradation studies were carried out in vitro with varying pH conditions. The in vitro cytotoxicity of PYRMP and its hydrolysis products was evaluated using the methyl tetrazolium (MTT) cytotoxicity test in HepG2 cell culture. PYRMP and PYRP have low glass transition temperatures of -68.8 and -59.6 degrees C, respectively. The polymers show a higher degradation rate at pH = 5.0 than at both pH = 7.4 and 8.0. The degradation process of PYRMP in different buffer solutions is discussed. The MTT test reveals that PYRMP at concentrations below 800 mu g mL(-1) and its hydrolysis products are non-toxic to HepG2 cells. Moreover, the hydrolysis products diluted 10 times are able to promote cell proliferation. This study shows that polyphosphazene containing N-ethoxypyrrolidone subsituents provides interesting perspectives for various biomedical applications. (C) 2009 Society of Chemical Industry