In vitro homogeneous and heterogeneous degradation of poly(ε-caprolactone/polyethylene glycol/L-lactide): The absence of autocatalysis and the role of enzymes

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Abstract
This study investigated the in vitro degradation behavior of poly(ϵ‐caprolactone/polyethylene glycol/L‐lactide) (PCEL) in comparison with that of three other biodegradable polymers. Polymer membranes were incubated in pancreatin solution, Ringer's solution, and distilled water at 37°C for up to 20 weeks. Characterization involved measuring weight loss, observing the morphological changes by scanning electron microscopy (SEM), analyzing molecular weight using size exclusion chromatography (SEC), and studying the crystalline structure using differential scanning calorimetry (DSC). The hydrolysis in a simple aqueous solution experienced no autocatalysis, which was attributed to the high permeability of PCEL to water‐soluble degradation products. Similar degradation rates were recorded for the PCEL and poly(L,L‐lactide) (PLLA) test membranes. In the presence of pancreatin, the PCEL membrane experienced rapid heterogeneous surface erosion likely caused by the selective loss of its surface PEG components under enzymatic action. Pancreatin also substantially increased the even physical resorption of the other test polymers by eliminating autocatalysis. This study demonstrated that autocatalysis commonly experienced by poly(α‐hydroxyl acid) can be reduced through chemical formulation or high enzyme activity. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006