Liquid photocurable biodegradable copolymers: in vivo degradation of photocured poly(epsilon-caprolactone-co-trimethylene carbonate).

Liquid photoreactive poly(epsilon-caprolactone-co-trimethylene carbonate)s endcapped with a coumarin group [coumarinated poly(CL/TMC)s] were prepared using tetra-functional hydroxylated substances such as pentaerythritol or four-branched poly(ethylene glycol), b-PEG. These coumarinated copolymers are tetra-branched and exist as a viscous liquid (MW 5 x10(3) approximately 7 x 10(3)). They were photocured by ultraviolet (UV) light irradiation to obtain a swelling or nonswelling solid under water, depending on the type of initiator used. The resultant films were implanted into the subcutaneous tissues of rats for up to 5 months. The photocured b-PEG-based copolymer was completely degraded and sorbed within a 1 month. On the other hand, surface-eroding degradation of pentaerythritol-based, coumarinated poly(CL/TMC) progressed with implantation time, and minimal recruitment of neutrophils, macrophages, and multinucleated giant cells was observed over the implantation period. Among the pentaerythritol-based copolymers, the fastest surface erosion was observed for the copolymer with the highest epsilon-caprolactone content. Microfabricated films with microarrays in which photoconstructs were stereolithographically prepared, using three different coumarinated copolymers at different regions, showed that upon implantation there was regionally differentiated biodegradation of microarrays, and the degree of region-specific biodegradation depended on the type of photocured copolymer. The observed tendency for biodegradation was in good agreement with that observed during implantation of individual films in vivo. This study also demonstrates that the use of multi-material-arrayed films enables the determination of different responses in vivo using only one sample.