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Biologische Systeme und Medizin Vortrag: Fr., 11:30–11:50 F-V59
Nanostructure and mechanics in hierarchical biocomposites: applications
of synchrotron X - ray microfocus scanning and in - situ diffraction and
scattering
Himadri Shikhar Gupta 1 , Oskar Paris 1 , Wolfgang Wagermaier 1 , Markus
Rueggeberg 1 , Chenghao Li 1 , Ingo Burgert 1 , Manfred Burghammer 2 , Sergio
S. Funari 3 , Christian Riekel 2 , Peter Fratzl 1
1 Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam,
Germany – 2 ESRF, Grenoble, France – 3 Beamline A2, HASYLAB-DESY,
Notkestrasse 85, Hamburg, Germany
Biological connective tissues like bone or wood are natural composite materials which
are hierarchically structured from the nanometer level to macroscopic length scales
[1, 2]. As a result, spatial variation and optimization of structural and mechanical
properties occurs at all levels, including the length scale of 0.1 µm - 10 µm. To obtain
information at this level on the micrometer level variation in the average nanostructural
properties, structural and chemical techniques like small angle X - ray scattering
(SAXS), wide - angle X - ray diffraction (WAXD) and X - ray fluorescence (XRF) can
be combined with micron sized beams, scanning setups, and thin sample sections to
generate two-dimensional spatial maps of nanostructural variations over sizes up to 50
to 100 µm. Complementary to the high spatial resolution available with a synchrotron
X - ray microbeam, time - resolved in - situ mechanical testing enables us to track
temporal variations at the molecular and supramolecular level induced, for example, by
the application of mechanical stress. In this contribution, we report some recent work
carried out by our group along these two lines. High resolution (1 µm) scanning X -
ray diffraction and scattering enabled us to reconstruct the 3 - dimensional crystallite
orientation in the individual lamellae of compact human osteonal bone, revealing a
right - handed spiralling fiber pattern [3]. Variations in the mineral particle size and
resolution could be studied at the level of individual bone packets. Two - dimensional
maps of the total SAXS intensity provided much higher contrast at the lamellar level
than microradiography measurements. The fibrillar level mechanics of parallel fibered
bone revealed a shearing mechanism at the nanometer level, between stiff fibers and
an intervening extrafibrillar matrix [4]. We highlight SAXS and WAXD measurements
of wood and bone obtained recently at the newly commissioned SAXS/WAXS/XRF
beamline at BESSY, specially designed for scanning microbeam experiments on biological
samples.
[1] O. Paris et al, Cell. Mol. Biol. 46 (2000) 993.
[2] P. Fratzl et al, J. Mater. Chem. 14 (2004) 2115.
[3] W. Wagermaier et al, Biointerphases 1 (2006) 1.
[4] H. S. Gupta et al, Nano Lett. 5 (2005) 2108.