Active growth factor delivery from poly(D,L-lactide-co-glycolide) foams prepared in supercritical CO2

A method for the production of microporous poly(D,L-lactide-co-glycolide) f oams containing encapsulated proteins using supercritical carbon dioxide is described. Foams generated as aqueous protein emulsions in a polymer-solve nt solution were saturated with carbon dioxide at supercritical conditions, and then suddenly supersaturated at ambient conditions causing bubble nucl eation and precipitation of the polymer. Proteins contained in the water ph ase of the emulsion were encapsulated within the foams, including basic fib roblast growth factor (bFGF), an angiogenic factor of interest in tissue en gineering applications. The release and activity of bFGF from these foams w as determined in vitro and compared with similar porous scaffolds prepared by traditional solvent casting-salt leaching techniques. Total protein rele ase rate was greater from structures made in CO, than those made by the sal t leaching technique, however a large initial burst of bFGF was released fr om the salt leached structures. This initial burst was not observed from th e polymer foams processed in CO, and active bFGF was released at a relative ly constant rate. Residual methylene chloride levels were measured in the f oams made with CO, and were found to be above the limits imposed by the US Pharmacopoeia implying that further solvent removal would be required prior to in vivo use. (C) 2000 Elsevier Science B.V. All rights reserved.