SPECTROSCOPY, IMAGING, OTHER TECHNIQUES |
Magnetic Resonance Microscopy of Collagen Mineralization
Ingrid E. Chesnick 1, Jeffrey T. Mason 2, Anthony A. Giuseppetti 3, Naomi Eidelman 3 and Kimberlee Potter 1*
1 Armed Forces Institute of Pathology
2 Armed Forces Institue of Pathology
3 American Dental Association
* To whom correspondence should be addressed. E-mail: potterk{at}afip.osd.mil.
Submitted on August 30, 2007
Revised on October 26, 2007
Accepted on 21 April 2008
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Abstract |
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A model mineralizing system was subjected to magnetic resonance microscopy (MRM), to investigate how water proton transverse (T2) relaxation times and magnetization transfer ratios (MTRs) can be applied to monitor collagen mineralization. In our model system, a collagen sponge was mineralized with polymer-stabilized amorphous calcium carbonate. The lower hydration and water proton T2 values of collagen sponges during the initial mineralization phase were attributed to the replacement of the water within the collagen fibrils by amorphous calcium carbonate. The significant reduction in T2 values by day 6 (p < 0.001) was attributed to the appearance of mineral crystallites, that were also detected by X-ray diffraction and scanning electron microscopy. In the second phase, between days 6 and 13 days, MRM properties appear to plateau as amorphous calcium carbonate droplets begin to coalesce within the intrafibrillar space of collagen. In the third phase, after day 15, the amorphous mineral phase crystallized, resulting in the reduction in the absolute intensity of the collagen diffraction pattern. We speculate that MTR values for collagen sponges, with similar collagen contents, increased from 0.25 ± 0.02 for controls strips to a maximum value of 0.31 ± 0.04 at day 15 (p = 0.03) because mineral crystals greatly reduce the mobility of the collagen fibrils.
Key Words:
X-ray diffraction, biomineralization, calcite, collagen mineralization, magnetic resonance microscopy, scanning electron microscopy
