Bone is fascinating to study, because it has evolved into a sophisticated material with a hierarchically complex stucture that makes it extremely resistant to fracture, given its light weight. The biomedical bone research field is an enormous endeavor � it produces thousands of scientific papers yearly. Yet the mysteries of bone’s complex structure and behaviors in health and in disease are still being unraveled, and a great deal of work remains to be done to completely understand how bone works to resist fracture.
Though a great deal is known about bone, little is known about its mechanics at the fundamental, molecular level. It is not known how all its molecular components function and interact to give bone its ability to withstand impacts. It is not known on the molecular level how the energy of an impact is dissipated nondestructively in healthy bone. And it is not known, on the molecular level, how the energy of an impact causes microcracking and fracture in unhealthy bone.
The study of bone fracture mechanisms aims ultimately to discover:
• How fracture originates in healthy bone. This naturally includes the study of the structures and mechanistic behaviors of bone components individually and in aggregate;
• How fracture propagates through bone;
• What arrests the development of fracture;
• How diseased and aged bone differ from healthy bone in responses to stresses.
Our main focus in the area of bone fracture mechanics is on characterizing the influence of adhesive noncollagenous bone proteins on overall bone toughness. Our findings so far on fracture-resisting properties of adhesive noncollagenous bone proteins are, in summary, that they exist as substantial contributors to the overall fracture toughness of bone, and that some adhesive noncollagenous bone proteins contain the sacrificial bond and hidden length mechanism. We have termed these proteins �glue�.
Please click here for a full explanation of how the sacrificial bond and hidden length mechanism works.
We use a variety of techniques to study bone fracture mechanisms, and to study the effects of the molecular bone glue on bone toughness through bone’s hierarchical scales, from the molecular nano-scale to the millimetric macro-scale:
• Nano-Micro – Imaging with AFMs and Scanning Electron Microscopes (SEMs) to explore bone building blocks and bone structures;
• Nano – AFM force spectroscopy � mechanical testing of bone protein molecules singly and in assemblies;
• Micro � Immunolabeling and staining techniques to determine the locations of �glue� molecules in bone
• Milli � Unique mechanical testers we have constructed that are combined with high-speed photography , and test 5x5x5mm trabecular bone cubes as well as single trabeculae, to see the details of bone fracture in real time under various experimental conditions. Experimental conditions are often designed to enhance glue properties. This tool is unique in that it is the only mechanical tester we are aware of that is coupled with high-speed photography.