TY - JOUR
T1 - In situ analysis of mineral content and crystallinity in bone using infrared micro-spectroscopy of the ν4 PO43- vibration
AU - Miller, Lisa M.
AU - Vairavamurthy, Vidyasagar
AU - Chance, Mark R.
AU - Mendelsohn, Richard
AU - Paschalis, Eleftherios P.
AU - Betts, Foster
AU - Boskey, Adele L.
N1 - Funding Information: We would like to thank G.L. Carr and G.P. Williams of the National Synchrotron Light Source, Brookhaven National Laboratory for their valuable input into this collaborative project and for the use of Beamline U4IR. We would also like to acknowledge the technical support of Michael Sullivan. This work is supported by the American Federation for Aging Research, A98087 (L.M.M.), the National Institutes of Health Biomedical Technology Program, P41-RR-01633 (M.R.C.), and the National Institutes of Health AR- 41325 (A.L.B., R.M.). The NSLS is supported by the United States Department of Energy under contract DE-AC02-98CH10886.
PY - 2001/7/2
Y1 - 2001/7/2
N2 - Measurements of bone mineral content and composition in situ provide insight into the chemistry of bone mineral deposition. Infrared (IR) micro-spectroscopy is well suited for this purpose. To date, IR microscopic (including imaging) analyses of bone apatite have centered on the ν1,ν3 PO43- contour. The ν4 PO43- contour (500-650 cm-1), which has been extensively used to monitor the crystallinity of hydroxyapatite in homogenized bone samples, falls in a frequency region below the cutoff of the mercury-cadmium-telluride detectors used in commercial IR microscopes, thereby rendering this vibration inaccessible for imaging studies. The current study reports the first IR micro-spectroscopy spectra of human iliac crest cross sections in the ν4 PO43- spectral regions, obtained with a synchrotron radiation source and a Cu-doped Ge detector coupled to an IR microscope. The acid phosphate (HPO42-) content and mineral crystallite perfection (crystallinity) of a human osteon were mapped. To develop spectra-structure correlations, a combination of X-ray powder diffraction data and conventional Fourier transform IR spectra have been obtained from a series of synthetic hydroxyapatite crystals and natural bone powders of various species and ages. X-ray powder diffraction data demonstrate that there is an increase in average crystal size as bone matures, which correlates with an increase in the ν4 PO43- FTIR absorption peak ratio of two peaks (603/563 cm-1) within the ν4 PO43- contour. Additionally, the IR results reveal that a band near 540 cm-1 may be assigned to acid phosphate. This band is present at high concentrations in new bone, and decreases as bone matures. Correlation of the ν4 PO43- contour with the ν2 CO 32- contour also reveals that when acid phosphate content is high, type A carbonate content (i.e., carbonate occupying OH- sites in the hydroxyapatite lattice) is high. As crystallinity increases and acid phosphate content decreases, carbonate substitution shifts toward occupation of PO43- sites in the hydroxyapatite lattice. Thus, IR microscopic analysis of the ν4 PO43- contour provides a straightforward index of both relative mineral crystallinity and acid phosphate concentration that can be applied to in situ IR micro-spectroscopic analysis of bone samples, which are of interest for understanding the chemical mechanisms of bone deposition in normal and pathological states.
AB - Measurements of bone mineral content and composition in situ provide insight into the chemistry of bone mineral deposition. Infrared (IR) micro-spectroscopy is well suited for this purpose. To date, IR microscopic (including imaging) analyses of bone apatite have centered on the ν1,ν3 PO43- contour. The ν4 PO43- contour (500-650 cm-1), which has been extensively used to monitor the crystallinity of hydroxyapatite in homogenized bone samples, falls in a frequency region below the cutoff of the mercury-cadmium-telluride detectors used in commercial IR microscopes, thereby rendering this vibration inaccessible for imaging studies. The current study reports the first IR micro-spectroscopy spectra of human iliac crest cross sections in the ν4 PO43- spectral regions, obtained with a synchrotron radiation source and a Cu-doped Ge detector coupled to an IR microscope. The acid phosphate (HPO42-) content and mineral crystallite perfection (crystallinity) of a human osteon were mapped. To develop spectra-structure correlations, a combination of X-ray powder diffraction data and conventional Fourier transform IR spectra have been obtained from a series of synthetic hydroxyapatite crystals and natural bone powders of various species and ages. X-ray powder diffraction data demonstrate that there is an increase in average crystal size as bone matures, which correlates with an increase in the ν4 PO43- FTIR absorption peak ratio of two peaks (603/563 cm-1) within the ν4 PO43- contour. Additionally, the IR results reveal that a band near 540 cm-1 may be assigned to acid phosphate. This band is present at high concentrations in new bone, and decreases as bone matures. Correlation of the ν4 PO43- contour with the ν2 CO 32- contour also reveals that when acid phosphate content is high, type A carbonate content (i.e., carbonate occupying OH- sites in the hydroxyapatite lattice) is high. As crystallinity increases and acid phosphate content decreases, carbonate substitution shifts toward occupation of PO43- sites in the hydroxyapatite lattice. Thus, IR microscopic analysis of the ν4 PO43- contour provides a straightforward index of both relative mineral crystallinity and acid phosphate concentration that can be applied to in situ IR micro-spectroscopic analysis of bone samples, which are of interest for understanding the chemical mechanisms of bone deposition in normal and pathological states.
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U2 - https://doi.org/10.1016/S0304-4165(01)00093-9
DO - https://doi.org/10.1016/S0304-4165(01)00093-9
M3 - Article
C2 - 11420138
SN - 0006-3002
VL - 1527
SP - 11
EP - 19
JO - BBA - Biochimica et Biophysica Acta
JF - BBA - Biochimica et Biophysica Acta
IS - 1-2
ER -