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AMORPHOUS CALCIUM PHOSPHATE FOR BI-PHASE CERAMICS PREPARATION
DD. . RabadjievaRabadjieva11, , SS. . TepavitcharovaTepavitcharova11, , RR. . GergulovaGergulova11, , RR. . TitorenkovaTitorenkova22, , EE. . DyulgerovaDyulgerova33, O. Petrov, O. Petrov22
November, 2010, Bulgaria
IGIC-BAS
1Institute of General and Inorganic Chemistry, BAS2Institute of Mineralogy and Crystallography, BAS 3Dental Medicine Faculty, University of Medicine, Sofia
INTRODUCTIONINTRODUCTION
Amorphous Calcium PhosphateACP
Ca(H2 PO
4 )2 .H
2 OC
a(HPO
4 )2 .2H
2 O
Ca8 (PO
4 )4 (HPO
4 )2 .5H
2 O
Ca
10 (PO4 )6 (O
H)2 Ca(H
2PO4)
2
-C
a 3(P
O 4) 2
a-Ca 3
(PO 4
) 2
Ca4(PO4)2О
Ca(HPO 4) 2
November, 2010, Bulgaria
Importance for the Biological system
They are the main inorganic component of body hard tissues
Biological apatite Nano-sizedPoorly crystallized Non-stoichiometric hydroxyapatite Including Na, K, Mg, Cl, F and CO3
INTRODUCTIONINTRODUCTIONCALCIUM ORTHOPHOSPHATES (COPh)
November, 2010, Bulgaria
INTRODUCTIONINTRODUCTION 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
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
EXPERIMENTS BIOMIMETIC SYNTHESIS
SBFc-Cam
K2HPO4
SBFc-Pm
CaCl2
K2 H
PO
4
EXPERIMENTAL CONDITIONS
Ca/P = 1.67pH 11.5 (KOH)Room temperature; Fast mixingFilteringWashing (water : acetone = 1:1)Freezing -18oC
November, 2010, Bulgaria
EXPERIMENTSTHERMODYNAMIC CALCULATIONS
Precipitation phase Solutions
DATABASE for K, H of the reaction for complex formation and precipitation
pH, toC, Initial solution concentrationsINPUT
CALCULATION DAVIES equations,
OUTPUT
PHREEQCI computer program
November, 2010, Bulgaria
Mg Na K Cl Ca/PO4
mmol/g 0.13 0.20 0.45 0.03 1.51 Enamel, Dentin and Bone0.02 - 0.29 0.22 - 0.39 2.10-4 - 0.02 0.03 – 0.1 1.6–1.7
RESULTSRESULTS ACP precipitation
Compositions of the initial precipitated solid phase
0 10 20 30 40 50 60 70 80 902-theta-Scale
XRD powder data and IR spectra
4000 3500 3000 2500 2000 1500 1000 500
Wavenumbers, cm-1
P-O
O-P-O
C-O
November, 2010, Bulgaria
RESULTSRESULTS ACP precipitation
Formation of Posner clusters Ca9(PO4)6 covered with
hydrated shell
CO32- ions from the solution compete with and
partially replace the PO43- ions
RESULT Ca vacancies
Ca vacancies could be occupied by free Na+, K+ and Mg2+ ions from the solution RESULT CawMgxNayKz(PO4)v(CO3)6v
November, 2010, Bulgaria
RESULTSRESULTS ACP precipitation
Thermodynamic calculated saturated indices (SI)
SI = lg(IAP/K)where IAP is an ion activity product, and K is a solubility product.
0.11 0.78 1.09 2.628.37
26.6334.19
60.18
010203040506070
Mg(
OH)2
Mg3
(PO4)2
:8H2O
MgC
O3:M
g(OH)2
:3H2O
CaCO3
Ca3(PO4)
2(am
)
Ca8H2(P
O4)6:
5H2O
Ca9Mg(
HPO4)(PO4)
6
Ca10(P
O4)6(O
H)2
November, 2010, Bulgaria
SUMMARYSUMMARY 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
EXPERIMENTSBIOMIMETIC TRANSFORMATION
SBF
Conditions
SBFc, SBFr, SBFg (~SBFc + Glycine)
37oC, 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
RESULTSRESULTS ACP transformation
0 10 20 30 40 50 60 70 800.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
SBFc SBFr SBFg
PO
43-, m
mo
l/l
time, h
0 10 20 30 40 50 60 70 800.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
3.25
3.50
Ca
2+, m
mo
l/l
time,h
SBFc SBFr SBFg
0 10 20 30 40 50 60 70 800.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
time,h
Mg2
+, m
mol
/l
SBFc SBFr SBFg
KINETIC STUDIES
Kinetic profile of PO43-, Ca2+ and Mg2+ contents in liquid
phases after different maturation times
PO43- Ca2+ Mg2+
November, 2010, Bulgaria
RESULTSRESULTS ACP transformation
KINETIC STUDIES
Kinetic profile of Ca/PO4 and Mg/Ca ratios in solid phases after different maturation times
0 10 20 30 40 50 60 70 80 90 700 750 800
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
0.050
0.055 SBFc SBFr SBFg
time, hm
ola
r ra
tio M
g/C
a0 10 20 30 40 50 60 70 80 90 700 750 800
1.40
1.42
1.44
1.46
1.48
1.50
1.52
1.54
1.56
1.58
1.60
1.62
1.64
1.66
1.68
mol
ar r
atio
Ca/
PO
4
time, h
SBFc SBFr SBFg
Ca/PO4 Mg/Ca
November, 2010, Bulgaria
RESULTSRESULTS ACP transformation
XRD STUDIES
XRD powder data of solid phases after different maturation times
SBFg
002 300
2-theta-Scale
initial
SBFc SBFr
10 20 30 40 50 60
10 20 30 40 50 60
10 20 30 40 50 60
1h
2h
4h
720h
002 300
002 300
November, 2010, Bulgaria
RESULTSRESULTS ACP transformation
THERMODYNAMIC STUDIES
PrMg(OH)2 +Mg3(PO4)2.8H2O +MgCO3.Mg(OH)2.3H2O +CaCO3 +Ca3(PO4)2(am) +Ca8H2(PO4)6.5H2O +Ca9Mg(HPO4)(PO4)6 +Ca10(PO4)6(OH)2 +
M(m)---00
M(eq)-------0
Calculated saturated indices (SI)Calculated moles of the crystallized salts
0.00E+002.00E-034.00E-036.00E-038.00E-031.00E-021.20E-021.40E-021.60E-021.80E-02
mo
les
of
cry
sta
lliz
ed
sa
lts
CaCO3Ca3(PO4)2(am)
November, 2010, Bulgaria
RESULTSRESULTS ACP transformation
ACP transforms into poorly crystalline apatite in the studied SBFs microenvironments.
ACP transformationSUMMARYSUMMARY ACP transformation
The SBF composition influences the rate of polymorphous phase transformation. Both HCO3
- 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
November, 2010, Bulgaria
RESULTSRESULTSPreparation of bi-phase products
XRD analysis of the calcinated at 600oC precursor
10 20 30 40 50 60
2-theta-Scale
72 hmatured
initial
24 hmatured
Mg-substituted--TCP
HA
18.1 wt. % Mg-substituted -TCP and 81.9 wt. % HA
47.2 wt. % Mg-substituted -TCP and 52.8 wt. % HA
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 600oC.