Fourier transform infrared (FTIR) spectroscopy is able to detect chemical bonding in materials. Here, representative spectra from (a) human bone and (b) the non-enzymatic crosslink, pentosidine, are shown. The main vibrations of pentosidine refer to C=N and C=C stretching as well as C-C and C-N stretching. These non-enzymatic cross-link vibrational regions are within human bone's amide I peak (C=O and C-N stretching, 1770-1570 cm-1) and phosphate peak (C-C and C-N stretching, 1250-1100 cm-1), respectively [50,51].