Calcium Orthophosphates
AME 50571: Biomaterials (R.K. Roeder)
Calcium Phosphate Solubility Diagram
[Ca]
Ca(OH)2–H3PO4–H2O (25°C)
10-2
10-3
CaHPO4·2H2O, DCPD
CaHPO4, DCPA
Ca8H2(PO4)6·5H2O, OCP
10-4
10-5
Ca5(PO4)3OH, HA
3
4
5
6
pH
7
8
9
β-Ca3(PO4)2, β-TCP
Ca4(PO4)2O, TTCP
10
Adapted from W.E. Brown, Clin. Orthop., 1966.
AME 50571: Biomaterials (R.K. Roeder)
Cortical Bone Composition
I. aqueous body fluid (≈33 vol%)
A. water/ions
B. cells
C. proteins
II. extracellular matrix (ECM) (≈67 vol%)
structurally...
A. interstitial bone (≈33 vol%)
B. osteons or Haversian systems (≈67 vol%)
compositionally...
A. organic-osteoid (≈50 vol% or ≈30 wt%)
1. collagen (≈90 vol%)
2. non-collagenous proteins (≈10 vol%)
B. inorganic-apatite (≈50 vol% or ≈70 wt%)
AME 50571: Biomaterials (R.K. Roeder)
Hierarchical Structure of Bone Tissue
trabecular bone
proximal
human femur
R
C cortical bone
L
[210]
1.0 mm
200
µm
osteons
Haversian
canals
c-axis [001]
mineralized
collagen fibrils
(≈ 100 nm width)
a-axis [100]
apatite crystals
(≈ 50 x 25 x 3 nm)
R.K. Roeder, et al., JOM, 2008.
AME 50571: Biomaterials (R.K. Roeder)
Hierarchical Structure of Bone Tissue
J-Y. Rho, et al., Med. Eng. Phys.,1998.
AME 50571: Biomaterials (R.K. Roeder)
Hydroxyapatite Crystal Structure
Ca10(PO4)(OH)2
space group: P63/m
Bone Mineral
b
1/4
3/4
1/2
0
3/4
0.43
0.07
0
1
3/4
1/4
0.93
0.57
1/4
0.93
0.57
1/4
1/4
1/4
3/4
3/4
1/4
0.43
0.07 1/4
0
1
0.93
0.57
1/4
3/4
1/2
0
3/4
1/4
3/4
1/2
0
0
1
0.93
0.57
3/4
0.43
0.07 1/4
3/4
3/4
1/2
0
3/4
1/4
0.43
0.07
1/4
1/4
1/4
0.93 1/4
0.57
1/4
1/4
0.93
0.57
1/4
3/4
3/4
1/2
0
1/2
0
0.43
3/4 0.07
1/4
3/4
0.43
0.07
3/4
3/4
1/4
0.43
3/4 0.07
1/4
1/2
0
3/4
1/4
1/4
0.93
0.57
1/4
3/4
1/4
3/4
3/4
0.43
0.07 1/4
3/4
3/4
1/4
3/4
1/4
1/2
0
3/4
1/4
1/4
0.93
0.57
3/4
3/4
OH
O
Ca
P
0.43
0.07
3/4
• calcium deficient
• highly substituted
• low crystallinity
3/4
0
1
3/4
1/4
0.93
0.57
1/4
a
3/4
1/4
0.93 1/4
0.57
3/4
0.43
0.07
3/4
3/4
3/4
1/4
1/4
1/2
0
3/4
3/4
1/4
1/4
1/2
0
1/2
0
Adapted from Young and Elliott, Archs. Oral. Biol., 1966.
AME 50571: Biomaterials (R.K. Roeder)
Bone Mineral Composition
(Ca,M)10(PO4,CO3,Y)6(OH,Cl,F)2 where M = Mg2+, Na+, K+...
Y = HPO42-, SO42-...
Consitituents (wt%)
calcium, Ca2+
phosphorus, P in PO43Ca/P molar ratio
sodium, Na+
potassium, K+
magnesium, Mg2+
carbonate, CO32fluoride, Fchloride, Clash (total inorganic)
total organic
adsorbed H2O
Cortical Bone
24.50
11.50
1.65
0.70
0.03
0.55
5.80
0.02
0.10
65.00
25.00
9.70
Synthetic HA
39.60
18.50
1.67
trace
trace
trace
–
–
–
100
–
–
Adapted from R.Z. LeGeros., Prog. Cryst. Growth Charact., 1981.
AME 50571: Biomaterials (R.K. Roeder)
[210]
004
45
50
55
4000 3500 3000 2500 2000 1500 1000
Wavenumbers (cm-1)
60
OH
PO4
30 35 40
Two Theta (°)
a-axis
[100]
c-axis [001]
HPO4HPO4
PO4
PO4
PO4
HPO4
c-axis [001]
H 2O
25
210
002
211
300
20
H2O
15
OH
Transmittance
10
200
100
Intensity
(arbitrary units)
XRD and FT-IR Spectra for HA
500
Adapted from Roeder et al., J. Am. Ceram. Soc., 2006.
AME 50571: Biomaterials (R.K. Roeder)
XRD Spectra
x-ray detector
θ
2θ
z
x-ray source: Cu Kα radiation (λ = 1.54 Å)
• monochromatic
• parallel
λ
• coherent (in phase)
d
constructive interference requires:
n·λ = 2z where z = d·sinθ
Bragg’s Law: n·λ = 2d·sinθ
where d = interplanar spacing
a
d = ––––––––––
(cubic)
2 + k2 + l2
√h
a = lattice parameter
hkl = Miller indices
used predominately in inorganic
crystalline materials to determine:
• phase identification (crystal structure)
• composition (phase fractions)
0.9λ
• crystal size
t = –––––
where B2 = Bm2 - Bs2
B·sinθ
• lattice parameters
Bm = peak breadth measured at
• crystal orientation (texture analysis)
one-half the max. intensity
• residual stresses
Bs = that of a ref. material with
crystal size > 0.1 µm
AME 50571: Biomaterials (R.K. Roeder)
FT-IR Spectra
=O
infra-red radiation of intensity, I1
H
-O
C
I2
energy is absorbed by characteristic molecular vibrations
e.g., stretching
bending
R
R
etc.
used predominately in organic molecules and macromolecules to determine:
• ligand identification (molecular structure)
• composition
AME 50571: Biomaterials (R.K. Roeder)