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Mechanical and physical properties of demineralized and deproteinated bones
Ekaterina Evdokimenko, Po-Yu Chen , Joshua Vasquez, Robert Urbaniak and Joanna McKittrick
Mechanical and Aerospace EngineeringMaterials Science and Engineering Program
UC San Diego
Ana Castro-Cesena and Gustavo A. Hirata,Center for Nanoscience and Nanotechnology
UNAM
Introduction
• Loss of bone (osteoporosis) and demineralization occurs as bones age
• Osteoporosis is a major cause of bone fractures• The mineral/collagen interaction is important in
understanding how this affects the bone fractures
• Mechanical properties of bones rely primarily on characteristics of bone mineral
Distinguishing features of bones
• Hierarchical structure
• Self-assembly/self-organization
• Synthesis under mild conditions
• Multifunctionality
• Basic building blocks– Mineral
• Calcium phosphates (hydroxyapatite Ca10(PO4)6(OH)2)
– Protein• Collagen 3
Self-assembly
Evolution, environmental
constraints
SynthesisT ~ 300 KP ~ 1 atm
Multi-functionality
Hierarchy of structure: nano,
micro, meso, macro
Adapted from E. Arzt, Mater. Sci. Eng. C, 26, 1245-1250 (2006).
Hierarchical Structure of Bone
4
tropocollagen
collagen fibrils
osteon
compact bone
cancellous bone
carbonated hydroxyapatite
Elk (Cervus canadensis)
Microstructure of bones and antlers
Bovine femur5% porosity
Elk antler9% porosity
Demineralized Bones - 100% proteins left
Deproteinated Bones - 100% minerals left
Experimental Methods
Long axis of antler/bone
Compact Bone Pictures
Untreated bone Demineralized bone
Deproteinated bone
0
20
40
60
80
100
0 2 4 6 8 10 12 14
75% Minerals Left
Compressive strain, %
-50
0
50
100
150
200
-2 0 2 4 6 8
Untreated Bone
Compressive strain, %
0
10
20
30
40
50
0 10 20 30 40 50
25% Minerals Left
LongitudinalRadialTransverse
Compressive strain, %
Compression Behavior of Compact Bone
Radial direction appears “the strongest”
direction in a bone
0
10
20
30
40
50
60
0 5 10 15 20 25
50% Minerals Left
Compressive strain, %
Compression Behavior of Compact Bone
0
20
40
60
80
100
120
140
0 10 20 30 40 50
Compression of Bone (L)
25%50%75%Untreated
Compressive strain, %
-50
0
50
100
150
200
-5 0 5 10 15 20 25
Compression of Bone (R)
25%50%75%Untreated
0
20
40
60
80
100
120
140
0 5 10 15 20 25 30
Compression of Bone (T)
25%50%75%Untreated
Compressive strain, %
A diagonal crack is the most common failure during the
bone compression
Mechanical Properties of Compact Bone
-0.4
-0.2
0
0.2
0.4
0.6
0.8
0.15 0.2 0.25 0.3
Log(E) - Log (Density)
LongitudinalRadialTransverse
Log (Density)
0.1
1
10
10 100
Specific Stiffness-Specific Strength
LongitudinalRadialTransverse
Specific strength, kN*m/kg
Partially demineralized bone behaves as a composite material
Mechanical Properties of Compact Bone
0
1
2
3
4
5
6
-10 0 10 20 30 40 50 60
Young's Modulus - Degree of Demineralization
LongitudinalRadialTransverse
Degree of demineralization, %
-0.4
-0.2
0
0.2
0.4
0.6
0.8
-10 0 10 20 30 40 50 60
Log(E) - Degree of Demineralization
LongitudinalRadialTransverse
Degree of demineralization, %