Biodegradable amphiphilic multiblock copolymers and their implications for biomedical applications

Alternating multiblock copolymers composed of short blocks of poly(ethylene oxide) (PEO) and poly(epsilon-caprolactone) (PCL) or poly(L-lactic acid) (PLLA) were synthesized by a coupling reaction. The block copolymers of relatively high molecular weights (M-n > 20,000) formed a physically crosslinked thermoplastic network, while low molecular weight polymers were water-soluble. The block copolymers demonstrated solubility in a variety of solvents including acetone, tetrahydrofuran, methylene chloride, dioxane, water/acetone mixtures, and water/ethanol mixtures. The degree of swelling, optical transparency, and mechanical property of the films, prepared by a solvent casting method, were affected by the nature of the hydrophobic block used, polymer composition, temperature, and thermal history. The crystalline melting temperatures of PCL and PLLA in the block copolymers were significantly lowered due to the chemical structure of difunctional PCL and PLLA, and partial phase mixing with PEO segments. The properties of the block copolymers may be useful for biomedical applications as well as controlled drug release formulations. When PEO/PLLA multiblock copolymers were applied as a wound healing material loaded with basic fibroblast growth factor (bFGF), the feasibility study showed improved wound healing when compared to controls of no treatment and the same wound covering without bFGF, indicating that a certain degree of the bioactivity of bFGF is preserved. (C) 2000 Elsevier Science B.V. All rights reserved.