Speaker: Henrik Birkedal, Department of Chemistry & iNANO, Aarhus University, Denmark.

Date: 2010-03-17

Time: 14:15 - 15:00

Place: Lecture hall C, Chemistry department, Getingevägen 60, Lund, Sweden.

Abstract: Bone has a highly complex structure and is organized hierarchically from the atomic to the centimeter length scale – sort of like a molecular-scale Eiffel tower. It consists mainly of calcium phosphate nanocrystals and collagen type I fibers. The structure of bone determines its mechanical properties and hence its propensity for fracture. Bone structure is well understood down to around 10 micrometer; below this length scale many uncertainties remain. However, it is exactly at these length scales that bone quality is determined; i.e. the factors determining the risk of fracture.

We use small angle X-ray scattering (SAXS) to probe the structure of bone on the 1-100 nm length scale. By raster scanning the sample in the X-ray beam, maps of bone nanostructure can be obtained with a resolution corresponding to the X-ray beam diameter [1]. Using SAXS on bone, one is sensitive to the bone nanocrystals [2]. Two types of information can be obtained: the orientation of the crystallites and their thickness. Our methodologies for obtaining this information will be presented.

We will discuss examples of applications of SAXS on bone focusing on two distinct bone systems: the structural organization of growth plates, the loci of bone formation in growing juveniles [3], [4], and on Sr-treatment of osteoporosis [5].

1. Paris, O., From diffraction to imaging: New avenues to study the hierarchical structure of biological tissues with X-ray microbeams. Biointerphases 2008, 3, FB1-FB26.
2. Fratzl, P.; Fratzl-Zelman, N.; Klaushofer, K.; Vogl, G.; Koller, K., Nucleation and growth of mineral crystals in bone studied by small-angle X-ray scattering Calc. Tissue Int. 1991, 48, 407-413.
3. Bünger, M. H.; Li, H.; Zou, X.; Langdahl, B.; Nygaard, J. V.; Bünger, C. E.; Besenbacher, F.; Pedersen, J. S.; Birkedal, H., Nanostructure of growing bones. In prepartion for Bone 2010.
4. Bünger, M. H.; Foss, M.; Erlacher, K.; Hougaard, M. B.; Li, H.; Zou, X.; Langdahl, B.; Bünger, C.; Birkedal, H.; Besenbacher, F.; Pedersen, J. S., Nanostructure of the neurocentral growth plate: Insight from scanning small angle X-ray scattering, atomic force microscopy and scanning electron microscopy. Bone 2006, 39, 530-541.
5. Bünger, M. H.; Oxlund, H.; Hansen, T. K.; Sørensen, S.; Bibby, B. M.; Thomsen, J. S.; Langdahl, B. L.; Besenbacher, F.; Pedersen, J. S.; Birkedal, H., Strontium and Bone Nanostructure in Normal and Ovariectomized Rats Investigated by Scanning Small-Angle X-Ray Scattering. Calc. Tissue Int. 2010, in press.

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