amorphous calcium phosphate for bi-phase ceramics preparation d. rabadjieva 1, s. tepavitcharova 1,...

AMORPHOUS CALCIUM PHOSPHATE FOR BI-PHASE CERAMICS PREPARATION

DD. . RabadjievaRabadjieva11, , SS. . TepavitcharovaTepavitcharova11, , RR. . GergulovaGergulova11, , RR. . TitorenkovaTitorenkova22, , EE. . DyulgerovaDyulgerova33, O. Petrov, O. Petrov22

[email protected]

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


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)


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


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.


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


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


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



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



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


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)


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


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+



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



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



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)



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.



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.

amorphous calcium phosphate for bi-phase ceramics preparation d. rabadjieva 1, s. tepavitcharova 1,...

Documents

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saturated indices si