Copolymers of 1,5-dioxepan-2-one and L- or D,L-dilactide: in vivo degradation behaviour

Copolymers of 1,5-dioxepan-2-one (DXO) and L- or D,L-dilactide have been synthesized and characterized. The molar ratio of the two monomers was around 20/80 of DXO and L- or D,L-lactide respectively. In vivo studies on rats revealed significant differences in tissue response between the semicrystalline DXO/L-LA copolymer and the amorphous DXO/D,L-LA copolymer. The materials were characterized pre- and post-implantation by size-exclusion chromatography (SEC), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), and light-microscopy. Degradation seems to follow an autocatalytic hydrolysis mechanism. The amorphous copolymer was degraded at a faster rate and gave a less pronounced foreign body reaction as compared to the semicrystalline one.