In vitro degradation of glycine/DL-lactic acid copolymers.
The in vitro degradation of glycine-DL-lactic acid copolymers was studied as a function of the composition. These polydepsipeptides were prepared by ring-opening copolymerization of 6-methyl-2,5-morpholinedione and DL-lactide. The degradation of discs of the copolymers was performed in a phosphate buffer at pH 7.4 and 37 degrees C. The decrease in molecular weight and weight was determined until complete weight loss had occurred. Poly(DL-lactide) was used as a reference material. All (co)-polymers show an immediate decrease in molecular weight, whereas the weight remains almost unchanged during a longer period of time. Decrease in weight started earlier as the glycine content of the co-polymer increased. The lactic acid content of the residual material increased during the weight loss showing a higher solubility of polymer fragments with a relatively high content of glycine residues. From the hydrolysis constants it was concluded that the degradation was best described by hydrolysis of ester bonds via a bulk erosion process, autocatalyzed by the generated carboxylic acid end groups. The rate constants varied from 4-7 X 10(-2) (day-1) for all (co)polymers. All (co)polymers show an increase in the molecular weight distribution upon weight loss.
Department of Chemical Technology, Twente University, Enschede, The Netherlands.
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J
Helder
P J
PJ
Dijkstra
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J
Feijen
D001672:Biocompatible Materials; D001673:Biodegradation, Environmental; D006868:Hydrolysis; D066298:In Vitro Techniques; D007700:Kinetics; D007773:Lactates; D019344:Lactic Acid; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008970:Molecular Weight; D011091:Polyesters; D011108:Polymers
D001672:Biocompatible Materials; D007773:Lactates; D011091:Polyesters; D011108:Polymers; C062243:glycine-lactic acid copolymer; D019344:Lactic Acid; C033616:poly(lactide)