Lithocholic-acid-containing poly (ester-anhydride)s

New degradable poly(ester-anhydride)s were prepared by melt polycondensation of poly(sebacic acid) (PSA), transesterified by different amounts (30-90%) of lithocholic acid (LCA), a natural hydroxy bile acid. Transes-terification of PSA is a one-pot reaction that starts with a high-molecular-weight polymer based on anhydride bonds and yields polymer based on random anhydride-ester bonds. A systematic study of the synthesis, characterization, degradation in vitro, drug release, and stability of these polymers was performed. Polymers with molecular weights (M_w) in the range of 12 000-115 000 and melting points in the range of 55-112 °C were obtained for 30-90% of lithocholic acid content. NMR and IR spectroscopic analyses indicate the formation of ester bonds in the polyanhydride backbone. The experimental results fit the calculated molecular weight, with the highest M_w, obtained for a 4:6 PSA-LCA ratio. The study shows that some of these new degradable copolymers can be potentially used as carriers for the controlled release of drugs.