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surface metabolic activity (forming, resorbing, quiescent) and thus
tissue age.
Another technique that has reemerged in the analysis of bone and,
more specifi cally, bone quality is Raman spectroscopy.
9.2 A TOOL FOR CHARACTERIZING BONE MATERIAL
One of the diffi culties in assessing the bone material quality is its hier-
archical and complicated structure. Lamellar cortical bone, for example,
comprises mineralized collagen fi bers with alternating fi ber orientation
in successive lamellae. One approach to address this issue is Raman
microspectroscopy and imaging. This offers several technical advan-
tages. It has excellent spatial resolution (0.5- 1.0
m) and, in general,
the vibrational bands are narrow so that small frequency shifts and
band shape changes often are observed easily. Raman microspectros-
copy evolved rapidly once it was pointed out that the intensity of
Raman light should be independent of sample volume and should
remain essentially constant with decreasing sample size down to the
dimension determined by the diffraction limit, and hence the wave-
length, of the laser excitation. With routine limits of detection in the
nanogram range and high molecular selectivity, micro-Raman spectros-
copy has now become a major analytical technique. It may be applied
to characterize bone material properties at the microscopic level as a
function of anatomical location and bone surface metabolic activity, the
analysis of biologically important details such as individual cement
lines, individual lamellae, and boundaries around microcracks.
Since Raman spectroscopy is nondestructive, the same specimen can
be examined by a multitude of different techniques. Information from
the mineral component and the organic matrix is obtained simultane-
ously, providing a complete picture of the major bone constituents in
the area surveyed. Because of the heterogeneous nature of bone, single-
point Raman microspectroscopy cannot adequately describe the chem-
ical microstructure of bone. Spatial information is needed. For this
reason, Raman spectroscopic imaging is increasingly popular for the
analysis of complex organized systems such as bone and teeth [65] .
Raman spectroscopy and imaging are valuable tools for the analysis of
bone, the determination of protein secondary structure, and the study
of the composition of crystalline materials. The information from the
mineral component and the organic matrix is obtained simultaneously,
creating a complete picture of bone composition.
μ
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