1. AMORPHOUS CALCIUM PHOSPHATE FOR BI-PHASE CERAMICS PREPARATION D. Rabadjieva 1, S. Tepavitcharova 1, R. Gergulova 1, R. Titorenkova 2, E. Dyulgerova 3, O. Petrov 2 didiarab@svr.igic.bas.bg November, 2010, Bulgaria IGIC-BAS 1 Institute of General and Inorganic Chemistry, BAS 2 Institute of Mineralogy and Crystallography, BAS 3 Dental Medicine Faculty, University of Medicine, Sofia

2. INTRODUCTION AmorphousCalciumPhosphate ACP Ca(H 2 PO 4 ) 2.H 2 O Ca(HPO 4 ) 2.2H 2 O Ca 8 (PO 4 ) 4 (HPO 4 ) 2.5H 2 O Ca 10 (PO 4 ) 6 (OH) 2 Ca(H 2 PO 4 ) 2  -Ca 3 (PO 4 ) 2 a -Ca 3 (PO 4 ) 2 Ca 4 (PO 4 ) 2 О Ca(HPO 4 ) 2 November, 2010, Bulgaria

3. Importance for the Biological system They are the main inorganic component of body hard tissues Biological apatite  Nano-sized  Poorly crystallized  Non-stoichiometric hydroxyapatite  Including Na, K, Mg, Cl, F and CO 3 INTRODUCTION CALCIUM ORTHOPHOSPHATES (COPh) November, 2010, Bulgaria

4. INTRODUCTION BIOMIMETIC APPROACH Biological mineralization (biomineralization) process of in vivo formation of inorganic minerals Deposition and Growing of Calcium Phosphates in the organic matrix in the body fluids medium November, 2010, Bulgaria

5. AIMS To study the biomimetic synthesis and transformations of X-ray ACP in conventional, revised and modified with Glycine SBF in order to elucidate some elementary processes of hard tissue mineralization and of the influence of micro- environmental surroundings on synthesis and transformation processes. November, 2010, Bulgaria

6. EXPERIMENTS BIOMIMETIC SYNTHESIS SBFc-Cam K 2 HPO 4 SBFc-Pm CaCl 2 K 2 HPO 4 EXPERIMENTAL CONDITIONS Ca/P = 1.67 pH 11.5 (KOH) Room temperature; Fast mixing Filtering Washing (water : acetone = 1:1) Freezing -18 o C November, 2010, Bulgaria

7. EXPERIMENTS THERMODYNAMIC CALCULATIONS Precipitation phaseSolutions DATABASE for K,  H of the reaction for complex formation and precipitation pH, t o C, Initial solution concentrations INPUT CALCULATION DAVIES equations, OUTPUT PHREEQCI computer program November, 2010, Bulgaria

8. Mg Na K Cl Ca/PO 4 mmol/g 0.13 0.20 0.45 0.03 1.51 Enamel, Dentin and Bone 0.02 - 0.29 0.22 - 0.39 2.10 -4 - 0.02 0.03 – 0.1 1.6–1.7RESULTS ACP precipitation Compositions of the initial precipitated solid phase XRD powder data and IR spectra November, 2010, Bulgaria

9. RESULTS ACP precipitation Formation of Posner clusters Ca 9 (PO 4 ) 6 covered with hydrated shell CO 3 2- ions from the solution compete with and partially replace the PO 4 3- ions RESULT  Ca vacancies Ca vacancies could be occupied by free Na +, K + and Mg 2+ ions from the solution RESULT  Ca w Mg x Na y K z (PO 4 ) v (CO 3 ) 6v November, 2010, Bulgaria

10. RESULTS ACP precipitation Thermodynamic calculated saturated indices (SI) SI = lg(IAP/K) where IAP is an ion activity product, and K is a solubility product. November, 2010, Bulgaria

11. SUMMARY ACP precipitation Ionic substitution Co-precipitation Incorporation of maternal solution LEAD TO  precipitation of calcium deficient, X-ray amorphous phosphate  mineral composition similar to those in the hard tissues (enamel, dentin, and bone mineral) November, 2010, Bulgaria

12. EXPERIMENTS BIOMIMETIC TRANSFORMATION SBF Conditions  SBFc, SBFr, SBFg (~SBFc + Glycine)  37 o C, pH 7.3;  Static regime; Solid/liquid ratio 4 g/l ;  Duration – 1, 2, 4, 6, 24 h, 3, 10, 30 days;  SBF solution changes - after 3-rd day November, 2010, Bulgaria

13. RESULTS ACP transformation KINETIC STUDIES Kinetic profile of PO 4 3-, Ca 2+ and Mg 2+ contents in liquid phases after different maturation times PO 4 3- Ca 2+ Mg 2+ November, 2010, Bulgaria

14. RESULTS ACP transformation KINETIC STUDIES Kinetic profile of Ca/PO4 and Mg/Ca ratios in solid phases after different maturation times Ca/PO4 Mg/Ca November, 2010, Bulgaria

15. RESULTS ACP transformation XRD STUDIES XRD powder data of solid phases after different maturation times November, 2010, Bulgaria

16. RESULTS ACP transformation THERMODYNAMIC STUDIES Pr Mg(OH) 2 + Mg 3 (PO 4 ) 2.8H 2 O+ MgCO 3.Mg(OH) 2.3H 2 O+ CaCO 3 + Ca 3 (PO 4 ) 2 (am)+ Ca 8 H 2 (PO 4 ) 6.5H 2 O+ Ca 9 Mg(HPO 4 )(PO 4 ) 6 + Ca 10 (PO 4 ) 6 (OH) 2 + M(m) - 0 M(eq) - 0 Calculated saturated indices (SI) November, 2010, BulgariaRESULTS ACP transformation

17. ACP transforms into poorly crystalline apatite in the studied SBFs microenvironments. ACP transformationSUMMARY The SBF composition influences the rate of polymorphous phase transformation. Both HCO 3 - ions and Glycine accelerate the transformation rates but the effect is more pronounced by SBF with Glycine The phase transformations leaded to changes in the chemical compositions of solid and liquid phases. Thermodynamic simulations reveal that these phenomena could be explained by the processes of dissolution/crystallization/co- crystallization/ion-exchange. November, 2010, Bulgaria

18. RESULTS Preparation of bi-phase products XRD analysis of the calcinated at 600 o C precursor 18.1 wt. % Mg-substituted  -TCP and 81.9 wt. % HA 47.2 wt. % Mg-substituted  -TCP and 52.8 wt. % HA

19. BIOMIMETIC APPROACH FOR PREPARATION OF MODIFIED CALCIUM PHOSPHATES i)precursor precipitation in SBF; ii)precursor maturation in SBF; iii)calcination of the maturated samples at 600 o C.