title: Influence of amide versus ester linkages on the properties of eight-armed PEG-PLA star block copolymer hydrogels.
abstract: Water-soluble eight-armed poly(ethylene glycol)-poly(l-lactide) star block copolymers linked by an amide or ester group between the PEG core and the PLA blocks (PEG-(NHCO)-(PLA)(8) and PEG-(OCO)-(PLA)(8)) were synthesized by the stannous octoate catalyzed ring-opening polymerization of l-lactide using an amine- or hydroxyl-terminated eight-armed star PEG. At concentrations above the critical gel concentration, thermosensitive hydrogels were obtained, showing a reversible single gel-to-sol transition. At similar composition PEG-(NHCO)-(PLA)(8) hydrogels were formed at significantly lower polymer concentrations and had higher storage moduli. Whereas the hydrolytic degradation/dissolution of the PEG-(OCO)-(PLA)(8) takes place by preferential hydrolysis of the ester bond between the PEG and PLA block, the PEG-(NHCO)-(PLA)(8) hydrogels degrade through hydrolysis of ester bonds in the PLA main chain. Because of their relatively good mechanical properties and slow degradation in vitro, PEG-(NHCO)-(PLA)(8) hydrogels are interesting materials for biomedical applications such as controlled drug delivery systems and matrices for tissue engineering.
authors: Department of Polymer Chemistry and Biomaterials, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors: Sytze J
authors: SJ
authors: Buwalda
authors: Pieter J
authors: PJ
authors: Dijkstra
authors: Lucia
authors: L
authors: Calucci
authors: Claudia
authors: C
authors: Forte
authors: Jan
authors: J
authors: Feijen
mesh_terms: D000577:Amides / Q000737:chemistry*; D001672:Biocompatible Materials; D004952:Esters / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D011091:Polyesters / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D012212:Rheology
chemical_list: D000577:Amides; D001672:Biocompatible Materials; D004952:Esters; D020100:Hydrogels; D011091:Polyesters; D011108:Polymers; D011092:Polyethylene Glycols; C033616:poly(lactide)