Biodegradable poly(D,L-lactic acid)-poly(ethylene glycol)-monomethyl etherdiblock copolymers: structures and surface properties relevant to their use as biomaterials

To obtain biodegradable polymers with variable surface properties for tissu e culture applications, poly(ethylene glycol) blocks were attached to poly( lactic acid) blocks in a variety of combinations. The resulting poly(D,L-la ctic acid)-poly(ethylene glycol)-monomethyl ether (Me.PEG-PLA) diblock copo lymers were subject to comprehensive investigations concerning their bulk m icrostructure and surface properties to evaluate their suitability for drug delivery applications as well as for the manufacture of scaffolds in tissu e engineering. Results obtained from H-1-NMR, gel permeation chromatography , wide angle X-ray diffraction and modulated differential scanning calorime try revealed that the polymer bulk microstructure contains poly(ethylene gl ycol)-monomethyl ether (Me.PEG) domains segregated from poly(D,L-lactic aci d) (PLA) domains varying with the composition of the diblock copolymers. An alysis of the surface of polymer films with atomic force microscopy and X-r ay photoelectron spectroscopy indicated that there is a variable amount of Me.PEG chains present on the polymer surface, depending on the polymer comp osition. It could be shown that the presence of Me.PEG chains in the polyme r surface had a suppressive effect on the adsorption of two model peptides (salmon calcitonin and human atrial natriuretic peptide). The possibility t o modify polymer bulk microstructure as well as surface properties by varia tion of the copolymer composition is a prerequisite for their efficient use in the fields of drug delivery and tissue engineering. (C) 2000 Elsevier S cience Ltd. AII rights reserved.