Risto Hakala

Photo-cross-linked biodegradable poly(ester anhydride) networks prepared from alkenylsuccinic anhydride functionalized poly(ε-caprolactone) precursors.

Biodegradable poly(ester anhydride) networks based on linear and star-shaped poly(ε-caprolactone)-based precursors were synthesized with the aim of obtaining matrixes suitable for release of macromolecular active agents. The ring-opening polymerization yielded hydroxyl telechelic oligomers, which were end-functionalized with succinic anhydride or with alkenylsuccinic anhydrides containing 8, 12, or 18 carbons in their alkenyl chains. Before cross-linking, the acid-terminated oligomers were reacted with methacrylic anhydride to obtain methacrylated precursors containing labile anhydride bonds. The degrees of substitution for the acid functionalization and methacrylation were >93%. Cross-linking of the precursors was carried out with visible light at room temperature. Gel contents and cross-linking densities were higher for networks cross-linked from the star-shaped precursors than for networks prepared from the linear precursors. In in vitro erosion tests, the presence of the alkenyl chain slowed down the erosion rate. The networks exhibited characteristic surface erosion: the mass loss was linear, whereas the dimensions of the specimens decreased steadily. A macromolecular release study showed the release of the model compound to be linear and in proportion to the mass loss.