1. Biomineralization what? Relatively new branch of study in bioinorganic
Extends beyond ‘biocoordination chem’ focusing on M + L
Extends length range of bio and inorg interplay
Interfaces with “hot” area of nano structures/devices/materials
Inorganic structures combined with an organic matrix

2. Biomineralization The bottom line?
Organic layers or limits between crystals gives flexibility
Patterning from carboxylate arrays
Highly Controlled precipitation
Involve complicated Equilbria

3. Biomineralization which? Major materials are: (see Table VI.1)
Calcium carbonate - crystalline as CaCO3 (calcite, aragonite)
amorphous as CaCO3.hydrate
Calcium phosphate- crystalline as Ca10(PO4)6(OH)2 (hydroxyapatite)
crystalline as Ca8(PO4)6(H)2 (octacalcium phosphate)
Silica amorphous SiO2.hydrate
Iron oxides magnetite Fe3O4
Geothite, lepidocrocite
ferrihydrite Fe2O3. hydrate

4. Biomineralization requirements Low solubility: Ca2+ preferred to Mg2+
High lattice stabilities: Ca10(PO4)6(OH)2 preferred to MgO
Thermodynamically stable:
Recall:
Lattice Enthalpy DHlattice ~ Lattice Energy, U
N Z+ Z- A e2
(1 - n)
U =
4 p eo d
N is Avogadro’s # x 1023 ion pairs/mol
Z+ Z- is the charge product
A is the Madelung constant
e2 and eo are charge on e- and permittivity constants
d is the distance (cm) between r+ and r-
n is a number, Born constant

5. Biomineralization uses Major materials are: (see Table VI.1)
CaCO3 (calcite, aragonite) structural support
amorphous as CaCO3.hydrate Ca storage
Ca10(PO4)6(OH)2 (hydroxyapatite) structural support, mech. strength
Ca8(PO4)6(H)2 (octacalcium phosphate) precursor
SiO2.hydrate structural support
magnetite Fe3O4 orientation
Geothite, lepidocrocite teeth
ferrihydrite Fe2O3. hydrate Fe storage

6. Morphogenesis: Pattern and Form in Biomineralization
Fig. 2 (a) Magnesium calcite polycrystalline concretion from the red coral Corallium rubrum showing irregular surfaces protuberances, scale bar 10 mm.
(b) the biomineral is patterned by radial and tangential constraints to give the wheel-like architecture.
(d) Radiolarian micro-skeleton consisting of a continuous spheroidal framework of amorphous silica, scale bar 10 mm.
(e) Radiolarian micro-skeleton showing how the hollow porous silica microshell is structurally connected to an internal set of radially-directed mineralized spicules; scale same as in (d).
From S. Mann, 1997

7. Limits dimension of crystal Reduces voids in crystal Inhibits cracks
The combination of inorganic structure with organic matrix can increase the strength.
The organic matrix:
Limits dimension of crystal
Reduces voids in crystal
Inhibits cracks
Matrix absorbs, dissipates energy
Patterning
Nacre (mother of pearl) in shells. Aragonite crystals formed in layers separated by protein sheets.

8. Like any other type of phytoplankton, coccolithophores are one-celled marine plants that live in large numbers throughout the upper layers of the ocean. Unlike any other plant in the ocean, coccolithophores surround themselves with a microscopic plating made of limestone (calcite). These scales, known as coccoliths, are shaped like hubcaps and are only three one-thousandths of a millimeter in diameter.
What coccoliths lack in size they make up in volume. At any one time a single coccolithophore is attached to or surrounded by at least 30 scales. Additional coccoliths are dumped into the water when the coccolithophores multiply asexually, die or simply make too many scales. Scientists estimate that the organisms dump more than 1.5 million tons (1.4 billion kilograms) of calcite a year, making them the leading calcite producers in the ocean. In large numbers, coccolithophores dump tiny white calcite plates by the bucketful into the surrounding waters and completely change its hue. In areas with trillions of coccolithophores, the waters will turn an opaque turquoise from the dense cloud of coccoliths.

9. Biologically Induced Biomineralization
context
Major role in carbon cycle:
Ca HCO3  CaCO3 + CO H2O
Calcification can parallel photosynthetic activity:
As carbon dioxide is removed, equilibrium shifts favoring carbonate.
CaCO3 deposited within cells: coral reefs.
Example of biomineralization as a secondary effect.
Another is FeS from sulfate reducing bacteria.
Biologically Induced Biomineralization

10. Biologially Induced Biomineralization
characteristics
Results from other metabolic processes
Not controlled
Amorphous or heterogeneous structures

11. Biologially Controlled Biomineralization
characteristics
Highly regulated processes
Examples: bone, teeth, shells, having specific functions
Well-defined structures (crystallinity), and shapes
Formed in vesicle compartments = functions like a flask!
Epitaxy control: matches dimensions of lattice to the amino acid template

12. Fig. VI.5 : Controls of biomineralization from supersaturated solutions
1) Gating via membrane pumps and redox processes
2) complexations w/ solubilizing agents
3) enzyme controlled concentrations
4) ionic strength (common ion effect) and activities
5) pH
6) organic matrix- mediation insoluble organic compartments
7) matrix mediated nucleation, regulated direction of lattice growth
8) Epitaxy control: match dimension of crystal to pattern of template, lattice spacing = amino acid residue spacing
9) Inhibitors C
chelation
activity
redox
ionic strength pH

13. Fig.6.4 shows different crystal morphologies of bacterial magnetite and their indexed faces. Crystal growth at different planes will produce various shapes.

14. How complicated shapes are formed Use of specific residues as template
 Asp – rich protein
Ca2+

15. How complicated shapes are formed Like a cast made from a mold
Fig Cell Walls, intracellular organelles and cellular assemblages act as scaffolds for microtubules (MT) which in turn are used as directing agents for the patterns of vesicles (V) involved in biomineralization (B).
From S. Mann 1997

16. Magnetotactic bacterial cell containing chains of magnetite (Fe3O4) crystals, ~ 100nm in length. Organized along cell walls in vesicles, added sequentially to align magnetic units.

17. BIOMOLECULAR SELF-ASSEMBLING MATERIALS
From a report of:
BIOMOLECULAR SELF-ASSEMBLING MATERIALS
Scientific and Technological Frontiers
Examples of current research inf this exciting field:
Polymer biosynthesis.
Self-assembled monolayers and multilayers. Decorated membranes. Mesoscopic organized structures. Biomineralization.
FIGURE 1 Illustration of the relationships among various aspects of biomolecular materials and their connections with the life sciences. A nucleus of broad-based research already exists, involving a variety of disciplines including chemistry, physics, biology, materials science, and engineering.

18. Debabrata R. Ray, Ashavani Kumar, Satyanarayana Reddy, S. R. Sainkar, N. R. Pavaskar and Murali Sastry*
Materials Chemistry Division, National Chemical Laboratory, Pune, India CrystEngComm, 2001, 3,
Development of protocols to grow crystals of controllable structure, size, morphology and superstructures of pre-defined organizational order is an important goal in crystal engineering with tremendous implications in the ceramics industry. Lured by the exquisite control that biological organisms exert over mineral nucleation and growth by a process known as biomineralization, materials scientists are trying to understand biomineralization and, thereby, develop biomimetic approaches for the synthesis of advanced ceramic materials.
SEM images recorded from barite crystals grown at the interface between water and hexane with stearic acid in the organic phase.
SEM images of BaSO4 crystals grown at the water–chloroform interface with stearic acid (images A and B) and octadecylamine (images C and D) as the templating molecules in the organic phase.
In the case of octadecylamine, the molecules at the interface would be positively charged at pH = 6.2 and therefore, the sulfate ions would be bound at the interface rather than Ba2+ ions as was the case with stearic acid molecules. We were interested in seeing whether the order of complexation of the ionic species prior to crystallization affected the morphology of the barite crystals grown at the liquid–liquid interface. As mentioned earlier, chloroform is denser than water and therefore the orientation of both the stearic acid and octadecylamine molecules at the liquid–liquid interface would be opposite to that in the case of water–hexane (below).

19. Fig. 4
Spiral outgrowth of calcium carbonate formed by growing crystals in the presence of 10 mg dm3 of a linear poly -aspartate of Mr 7100, scale bar 100 mm.
(b) Hierarchical morphology of BaSO4 crystals formed in a 0.5 mM aqueous solution of polyacrylate of Mr 5100; scale bar 10 mm. The cone-shaped units develop on the rim of pre-existing cones, and each cone consists of myriad BaSO4 nanofilaments (inset, scale bar 1 mm).
(c) Self-assembled helical ribbon of a silica-phospholipid biphase, scale bar 200 mm.
(d) Thin section showing a continuous silica framework produced by bacterial templating. The porous channels (white circles) are viewed end-on and are approximately 500 nm in width, scale bar 500 nm

20. A Hypothetical Model for Dental Enamel Biomineralization
1. Amelogenins are synthesized and secreted by ameloblast cells.
2. Amelogenin molecules assemble into nano-sphere structures approximately 20 nm in diameter with an anionic (negatively charged) surface.
3. The nanospheres interact electrostatically with the elongating surfaces of the enamel crystalites, acting as 20nm spacers that prevent crystal-crystal fusions. Enzymes (Proteinase-1) eventually digest away the charged surface of the nanospheres, producing hydrophobic nanospheres that further assemble and stabilize the growing crystalites.
4. Finally, other enzymes (Proteinase-2) degrade the hydrophobic nanospheres, generating amelogenin fragments and other unidentified products (?), which are resorbed by the ameloblasts.
5. As the amelogenin nanosphere protection is removed, crystallites thicken and eventually may fuse into mature enamel.