Novel Surface Coatings Using Oxidized Glycosaminoglycans as Delivery Systems of Bone Morphogenetic Protein 2 (BMP-2) for Bone Regeneration

Tissue engineering of bone requires the delivery of growth factors in a localized, sustained manner. Here, chitosan is used as polycation, while heparin and chondroitin sulfate are employed either as native or oxidized polyanions for formation of multilayers by layer-by-layer technique. The use of oxidized heparin and oxidized chondroitin sulfate permits additional stabilization by cross-linking through imine bond formation between amino groups of polycations and aldehydes of oxidized glycosaminoglycans (oGAGs). Since these multilayers are highly hydrophilic, adhesion of C2C12 myoblasts is improved either by the use of a specific 4 + 9 pH regime with native glycosaminoglycans or a terminal collagen I layer in case of oGAGs. Adhesion and proliferation studies with C2C12 myoblasts, seeded either on bone morphogenetic protein (BMP-2) loaded or non-loaded multilayers, show that intrinsic cross-linking in oGAG-based multilayers supports cell adhesion, spreading, proliferation, and subsequent cell differentiation into osteoblasts. This is related to higher thickness and roughness of multilayers made of oGAGs compared to their native counterparts studied by ellipsometry and atomic force microscopy. Taken together, oGAG multilayer systems provide stable surface coatings and are useful as biocompatible reservoirs for sustained release of BMP-2, paving the way for coating implants and scaffolds for repair and regeneration of bone.