Understanding hierarchy and functions of bone using scanning x-ray scattering methods

Overview & Synopsis

Biological materials are often hierarchically structured from the nanometer to the macroscopic scale. Specific characterization methods are needed to characterize the structures at these different length scales. This chapter reviews -based on the example of bone- the use of X-ray scattering methods to explore representative and quantitative structure information as well as structure-function relations in hierarchically structured biological materials. X-ray scattering techniques are particularly well suited for the characterization of the form and organization of organic and inorganic components in those materials. When nanometer-sized structures are exposed to X-rays, details of the internal material structure can be revealed by the analysis of the resulting interference patterns. Fundamental aspects of wide and small angle X-ray scattering (WAXS and SAXS) are discussed with specific focus on bone studies. An important field of research using X-ray scattering techniques, is the in situ combination with mechanical testing, which allows investigating changes in structure under specific loading conditions. Another common application is the structural study of heterogeneities or local structures within a sample using a narrow focused X-ray beam. Furthermore, in scanning mode, where the specimen is displaced step by step across a microbeam while collecting a SAXS/WAXS pattern at each step, complex structural maps of the sample can be derived. A natural extension of the method toward imaging is described in the context of X-ray imaging with scattering contrast.