Lecture 12 Organic templating of inorganic materials and bone biomimesis.pdf

Molecular Principles of Biomaterials Spring 2003
Lecture 12: Organic templating of anic materials and bone biomimesis
Last time: interfacial biomineralization and biomimetic anic chemistry
Today: biological strategies for anic templating anic materials
anic template materials
Biomimesis of bone
Reading: S. Mann, ‘Biomineralization: Principles and Concepts of anic Materials
Chemistry,’ Ch. 6, pp. 89-124 (2001)
Biological strategies for anic templating anic materials
Alteration of barriers to nucleation
• Organic surfaces alter free energy barrier to nucleation (Mann Science 1993)
∆G*
∆Gnuc
o Reminder of free energy of nucleation (homogeneous, but principle applies to heterogeneous surface
nucleation as well):
2 4 3 ∆Gv
∆Gnuc =∆Gsurface −∆Gbulk = 4πr σ−πr
3 Vm
ƒ Where ∆Gv is the free energy change for formation of the solid per mole from the ions, and Vm is the
molar volume of the nucleated solid
Lecture 12 – anic Biomaterials 1 of 13
Molecular Principles of Biomaterials Spring 2003
• How are free energy barriers modified anic templates? (Mann 1993) Complementarity in:
1. Surface lattice geometries
2. Spatial charge distributions
3. Polarity of hydration layers
4. Defect sites
5. Bonding chemistry
ƒ Coordination environment of metal ion in crystal mimicked by binding anic surface groups
o Matching lattice geometries:
Organic templating layer
New crystal
(Mann et al. 1993)
o Matching charge distributions:
ƒ Case of calcium cabonate: different crystal structures and crystal orientations nucleated on different
charge surfaces
Lecture 12 – anic Biomaterials 2 of 13
Molecular Principles of Biomaterials Spring 2003
o Templates used by nature:
ƒ Proteins
ƒ Lipids
ƒ harides
o Process is universal for templated nucleation:
ƒ Material: carbonates, phosphates silica, ice
ƒ Template: carboxy-rich moieties hydrogen-bonding