Synthesis of fluorescence-labelled short-chain polyester segments for the investigation of bioresorbable poly(ester-urethane)s

The synthesis and characterization of fluorescence-labelled low-molecular-weight polyesters based on known biocompatible and degradable materials such as poly[(R)-3-hydroxybutyric acid] (PHB) and poly(epsilon-caprolactone- co-glycolide) is described. A telechelic OH-terminated poly[(R)-3-hydroxybutyric acid] ((M) over bar(n) = 2300) was modified at the end groups through esterification with BOC-glycine. After removal of the BOC protection, the so-obtained free amino groups were conjugated with dansyl chloride to obtain dansyl-labelled end groups. No degradation of the starting material was observed during the several synthetic steps, while the crystallinity of the material was not significantly affected by the modification of the end groups. Fluorescence-labelled low-molecular-weight poly(epsilon-caprolactone) and poly(epsilon-caprolactone-co-glycolide) were obtained by bulk ring-opening polymerization of the corresponding cyclic monomers (epsilon-caprolactone and diglycolide) with dansylcadaverine. Both random (amorphous) and block (semi-crystalline) copolymers were obtained depending on the presence of the catalyst (Bu2SnO). The so obtained fluorescence-labelled polyesters are promising materials for the investigation of the biocompatibility and degradation of block poly(ester-urethane)s (DegraPol(R)) with fluorescence-aided microscopic and spectroscopic techniques.