DESCRIPTION: (verbatim) Temporary scaffolds for bone formation must meet a challenging set of requirements both in vitro and in vivo. These requirements will vary depending on whether the scaffold is to be used in vivo or for subsequent surgical transplantation, or for direct incorporation into the body as a biomaterial. In either case, the scaffolds must be biocompatible, mechanically robust, and tailorable to sustain sufficient integrity during repair or bone formation, assemble to fill in all parts of the repair site in vivo to avoid voids that can result in scar tissue, and eventually degrade to nontoxic materials. Silks exhibit excellent mechanical properties and can be genetically tailored to control sequence, composition and structure/properties. This control is particularly important for peptide coupling to these surfaces for control of types, densities and homogeneity of cell adhesion and bone formation. The ability to precisely control the placement and density of these factors is an essential feature in order to fully understand relationships between these peptides and bone growth in vivo or in vitro. Our hypothesis for the proposed study is that silk based polymers, because of their unique properties, including biocompatibility, high mechanical strength yet flexible with excellent resistance to compression, and our ability to genetically tailor the structures, can provide important 2D and 3 D scaffolds for bone formation. We plan to address this hypothesis by exploring the relationships between silk structure, growth factor types and decoration, and cell responses related to bone formation. Silk proteins will be prepared, including regenerated silkworm silk and different spider silks using recombinant DNA techniques (with and without encoded RGD and cysteines). The different silk substrates will be fabricated into 2D and 3D matrices and subsequently decorated by chemical coupling bone related growth factors (PTH 1-34, BMP-2)at different concentrations and in different combinations. Complete chemical, physical, and morphological analyses of these materials (e.g., CD, FTIR, ESEM, AFM, Contact Angle, XPS, TEM)will be conducted before and after cell studies. Cell responses to these matrices will be characterized in vitro using osteoblasts and stem cells and the studies will include assays for adhesion and spreading, DNA synthesis, collagen synthesis, alkaline phosphatase, osteocalcin, bone and mineralization. Macrophage assays in vitro and osteogenic potential and inflammation assessments in rat models in vivo will provide preliminary assessments of bone formation. A rat femur model will be used to study the best candidate silk biomaterials. The outcome of these studies will be the identification of the most promising silk-decorated matrices (appropriate types, densities and combinations of growth factors, and adhesion sites) for bone formation. All phases of the planed studies are supported with Preliminary Data that to demonstrate both the feasibility of the proposed experimental directions and the potential for this type of silk scaffolding to provide a new family of matrices for bone formation and eventually orofacial repair.