Mechanism of formation of concentrically laminated spherules: Implication to Randall’s plaque and stone formation

Fairland F. Amos,1,2 Lijun Dai,1,3 Rajendra Kumar,1,4 Saeed R. Khan5 and Laurie B. Gower1

1Department of Materials Science and Engineering, University of Florida, P.O. Box 116400, Gainesville, FL 32611, USA

2Laboratory for Chemical Physics, Center for Biomolecular Materials Spectroscopy, New York University, New York, NY 10010, USA

3Enzo Life Sciences, Inc., 10 Executive Blvd., Farmingdale, NY 11735, USA

4Division of Bioengineering, Montana Tech of the University of Montana, Butte, MT 59701, USA

5Department of Pathology, University of Florida, Gainesville, FL 32611, USA

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Quantification of the crystalline phases. The quantification of the crystalline calcium phosphates present in the precipitates was done using the Rietveld method [1-3] carried out with the “Rietquan 2.3” Quantitative Phase Analysis (QPA) software [4]. Peak shapes were modeled using the pseudo-Voigt function and two asymmetry parameters were refined. In each case four background parameters, a scale factor, five peak shape parameters, 2q offset (zero point correction), sample displacement and cell parameters were refined. The occupancy of the hydroxyl (OH-) ion was refined as one group (i.e. OH- occupancy) using the same reasoning as Knowles et al. [5] All refinements were carried out until a convergence was reached. The program was also tested for its accuracy using a three-phase mixture of known composition. The phases used were aluminum (20%), a-alumina (50%) and monoclinic-zirconia (30%). Results of the analyses showed 21.0% aluminum 49.3% Al2O3 and 29.7% ZrO2, confirming the competence of the program within an agreeable error (5% max).

Supporting Figure 1. Polarized optical micrograph of a crystallizing calcium phosphate spherulitic film grown in the presence of 50 mg/mL PD. The sample contains non- and weakly birefringent regions that start to transform into a more crystalline film.

REFERENCES

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3. Kumar R, Cheang P and Khor KA (2004) Phase composition and heat of crystallisation of amorphous calcium phosphate in ultra-fine radio frequency suspension plasma sprayed hydroxyapatite powders. Acta Mater 52: 1171-1181

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5. Knowles JC, Gross K, Berndt CC and Bonfield W (1996) Structural changes of thermally sprayed hydroxyapatite investigated by Rietveld analysis. Biomaterials 17: 639-645

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