Raman Spectroscopy of Bone and Cartilage - Emerging Raman Applications and Techniques in Biomedical and Pharmaceutical Fields - page 345

The consensus from the more developed FTIR imaging is that min-
eral/matrix ratio and crystallinity increase from the center to the edge of
an individual osteon [15] and from the periosteal region to endosteal region
of cortical bone [29-31]. The collagen cross-link ratio follows the same trends
as mineral/matrix ratio and crystallinity [32], while the carbonate/phosphate
ratio and acid phosphate content are found to decrease away from the cen-
ter of an osteon, with the most marked changes in acid phosphate occur-
ring within 30 m of the osteon [15, 31]. Raman imaging of bone began with

the work of Timlin [26], who imaged trabecular bone at moderately high
definition (100

μ

× 100 and 100 × 200 pixels) and moderately high resolution

(1 . 4 m) pixels (Fig. 14.2).

In interstitial tissue, SMCR has been used to generate Raman images of
bone [33]. Two mineral factors were observed, one corresponding to normal
mineral and the other containing a peak at 952 cm − 1 , interpreted as arising
from amorphous calcium phosphate (ACP). Images of this factor showed that
ACP was located away from the edge of the osteon. The authors suggested
that ACP might be found in regions susceptible to damage or that perhaps
ACP was a result of prior damage.

μ m × 1 . 4 μ

Fig. 14.2. Factors and score images of a 275 μm × 140 μm region of mature canine
trabecular bone strut. (a )PO 4 − 3and (b ) phenylalanine. Each pixel is 1 . 4 μm ×
1 . 4 μm. Reprinted with permission from [26]