Figure 3. FTIR imaging: Non-enzymatic cross-link ratio in ribated bone.

Samples of human cortical bone from the mid-diaphysis of the femur were subjected to an in vitro control or ribation treatment, the latter increases the non-enzymatic cross-links content. FTIR spectra were obtained over a 250 × 250 μm² area of bone at a 6.25-μm step size and the non-enzymatic cross-link ratio (NE-xLR), which is the area ratio of the amide-I subbands at 1678 and 1692 cm^-1, was calculated for each spectra. a) The average NE-xLR ratio was 35% higher in the ribation group in comparison to the control group (p < 0.005). The NE-xLR distribution can be seen in the FTIR images of b) control and c) ribated samples. Clearly an osteon with a low level of NE-xLR is to be seen in the upper left corner in b) and in c) a slightly diagonal cut osteon is going through the whole image from left upper corner to right lower corner with higher levels of the NE-xLR in the interstitial area (lower left corner).