THE BIODEGRADATION OF POLY(ESTER-ETHER-ESTER) BLOCK-COPOLYMERS IN A CELLULAR ENVIRONMENT IN-VITRO

In this paper we report about the biodegradation of tri-block poly(ester-ether-ester) copolymers obtained by reaction of preformed poly(ethylene glycol) (PEG) with two different lactone monomers, i.e. epsilon-caprolactone (CL) and L-lactide (LA). The two series of copolymers will be indicated as PCL-POE-PCL and PLA-POE-PLA. We identified and measured by HPLC analysis the amount of degradation products of the poly(ester-ether-ester) copolymers; three copolymers were tested for each series during 3-8 week experiments. The experiments were carried out both in the presence and absence of fibroblast cell populations. We evaluated at the same time the decrease of copolymer molecular mass after degradation by means of intrinsic viscosity [eta] measurements. From the [eta] measurements we can conclude that the higher the hydrophilicity of the material, the faster the rate of decrease of its intrinsic viscosity with time. The HPLC results indicate that the amount of the degradation products, i.e., respectively, the monomers 6-hydroxyhexanoic acid and L-lactic acid, is a function of both hydrophilicity of the molecule and the lateral block length. When the fibroblast cell populations were present in the same wells together with the biodegradable copolymers, signs of cellular metabolism of the degraded monomers were detected.