Modification of materials formed from poly(L-lactic acid) to enable covalent binding of biopolymers: Application to high-density three- dimensional cell culture in foams with attached collagen

We describe a method for increasing the hydrophilicity of materials formed from biodegradable polymers and introducing chemical functional groups on their surfaces. Poly(L-lactic acid) was blended with poly(ε-CBZ-L- lysine) at an 80:20 ratio. Films of the mixture were prepared and foams were made by solvent casting and salt leaching. Amino groups on the surface of the polymer mixture were deprotected by acid hydrolysis. As an example of the applicability of the technique for attachment of biomolecules, we covalently linked collagen to the deprotected amino groups, creating a surface capable of high density growth of a differentiated cell type (bovine adrenocortical cells). The method should be generally useful for surface modification of biodegradable polymer materials used in tissue engineering.