An estimated eleven million people in the United States have at least one medical device implant. Two types of implants, fixation devices (usually fracture fixation) and artificial joints, are used in orthopaedic treatments and oral and maxillofacial procedures: they account for 51.3 percent of all implants. Between these two groups of implants, 77 percent are fixation devices and 23 percent are joint replacement prostheses. When treating fractures, repair of large bone defects is a major reparative problem. Of the 1,230,000 fractures that are treated with osteosynthesized materials each year in the US, approximately 80 percent of these require adjuvant grafting. Among the joint replacement procedures, hip and knee surgeries represented 90 percent of the total, and were performed 310,000 times in the US in 1988. Currently, an increasing number of these procedures are revision surgeries with their concomitant need for bone grafting. Current approaches to these difficult bone repair problems include utilization of autografts, allografts and synthetic grafts. However, by virtue of the limitations associated with these biological and synthetic grafts, tissue-engineering approaches are continuously gaining ground as viable long-term solutions for bone repair and reconstruction procedures. In the context of bone repair, tissue engineered products can comprise a resorbable biomaterial scaffold, cells, and biological signaling molecules. In this project, the investigators propose to study scaffolds with grafted biological groups and focus exclusively on cellular adhesion. The hypothesis is that the efficacy of the adhesion itself depends upon both the molecular characteristics of the ligand, as well as the properties of the substrate to which the ligand is grafted. The research examines the initial events of adhesion by using model material surfaces with molecularly engineered attachment peptides. Highly reproducible surfaces can be made and, therefore, interfacial control can be achieved by using self-assembled monolayers to direct the conformation and density of grafted attachment peptides. These model surfaces also enable studying the co-adsorption or sequential adsorption of calcium phosphate and peptides. Thus, fundamental relationships among surface chemistry, the structure of reacting material surfaces, grafted peptides, and osteoblast attachment can be elucidated. This knowledge is then used to explain the behavior of materials that are clinically used today and novel material concepts are proposed for use in bone reconstruction therapies.
