Biomaterials and Biomimetic Materials Chemistry

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Nov 14, 2013 (3 years and 6 months ago)

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Biomaterials and Biomimetic
Materials Chemistry
Biological materials
Soft tissues: cartilage, tendon, skin
Hard tissues: skeletal bones, teeth,
mollusk shells, scales
Complex, ordered, multifunctional,
naturally occurring structures
Properties refined and optimized over
evolutionary timescales
Biomineralization: synthetic pathway of
biomaterials with specific form and function
Silica wall of a radiolarian
shell microorganism
10
10
µ
µµµ
µ
µµµ
m
m
4
Nano-optics in the Biological World
Brilliant blue color of a South American
butterfly (Morphorhetenor)
Two or more layers of 100 µm ×50 µm scales
Scales composed of cuticle, a complex
biopolymer composite
Naturally occurring diffraction grating,
producing color along with pigments present
Two or three scale sizes, arranged into a
finely tiled mosaic
Each mosaic tile contains scale of a particular
size and density of scales (200 to 500 scales
per mm
2)
Chem. Rev.1999, 99, 1935
3-D Preserved
Prehistoric Insects
Recovered from shallow, lime-rich
pool in a tropical rainforest
Well-preserved due to high salinity,
keeping away scavengers
Anthropodsoft tissue mineralized
by calcium phosphate
Source of inorganicsdue to
accumulation of vertebrate material
Recovered by acid dissolution of
the limestone
Nature1996, 381, 30
Biomineralization
Delineation of the space where inorganic material is
growing by biological environments (e.g. micelles,
vesicles), at specific times in the life of the organism
Chemical regulation by transport processes; control of
supersaturationlevels, e.g. complexation/decomplexation,
pH, redox
Molecular recognition at inorganic-organic interface: at
least some complementaritybetween inorganic structure
and organic surface chemistry on which it grows
Inorganic Exoskeletons
Some classes of microscopic marine organisms possess an
exoskeleton
Scaffold for stronger, more rigid superstructures
Encloses soft interior organic tissues
Radiolaria: single-celled organisms with silica exoskeletons
Diatoms: microscopic algae called phytoplankton
Form in coastal and polar waters
Coccolithophoresare also phytoplankton, but are abundant in
warmer tropical seas and possess calcium carbonate cages
Single-celled marine alga
surrounded by close-packed
arrangement of CaCO
3
scales
Individual scales are termed
coccoliths
Radial array of complex-
shaped units
Species-specific shaped units,
composed of a well-ordered,
single crystal of calcite (ED)
Mature CaCO
3
unit
Immature coccolith
CaCO
3
crystals oriented in
same direction as final
coccolith
No upper curved sections yet:
oriented nucleation and
shape formation occur
separately in time and space
Crystal structure, size, shape,
and orientation all controlled
during growth process
Biomaterials:
Magnetotactic
Bacteria
Bacteria from freshwater and
marine mudsaccumulate on the
north sides of water drops on
microscope slide
Reverse magnetic field, bacteria
swim in opposite direction
Magnetotacticcells possess
permanent magnetic dipole moment
Magnetosomes: intracellular
particles of magnetite, Fe
3O4,
40 to 100 nm in size
Greigite, Fe
3S4, in high-sulfurous
environments
Single-domain magnetic particles
due to nanoscopicsize, and
arranged in a chain of particles to
maximize magnetic moment
Biomaterials:
Magnetotactic
Bacteria
Bacteria follow the vertical
component of the geomagnetic
field: a biomagneticcompass
Bacteria from northern
hemisphere swim along field lines,
in direction of field
Move downwards towards
sediment (nutrient) and away from
toxic, oxygen-rich shallower water
Membrane-bound vesicle
biomineralizationof nanoparticles
of controlled size, morphology,
composition and arrangement
BiomimeticMaterials Chemistry
Study of biological structures and their synthetic pathway and
function for the synthesis of new materials
Materials developed using inspiration from Nature
Honeycomb, wood fiber, spider silks, quills, nacre, bone
Drug delivery, synthetic spider silk, artificial bone, tissue engineering,
inorganic materials with complex form
Biomimeticswill engulf molecular biology and replace it as the most
challenging and important biological science of the 21st Century:
Stephen Wainright, Duke U, Dept. of Biology
Spider Silk
0.2 to 10 µm diameter tensile fibers of high
elasticity combined with high strength
(~ equal strength to steel but 1/6 density;
~ double toughness compared to Kevlar)
Withstands extensions ~ 35 to 1300% before
breakage: absorb kinetic energy of flying
insects
Fibers can be modified (spinning
conditions, feedstock, silk microstructure) to
give desired mechanical strength
Unusually low glass transition temperature;
must be very cold before silk becomes
brittle enough to break
Parachutes, bulletproof fabrics, bridge
cables, aircraft carrier bungees;
biocompatible: artificial tendons, sutures, 
Adv. Mater.1998, 10, 1185
Adv. Mater.1998, 10, 1185
Spun from concentrated, aqueous protein
solution
Proteins emerge from spider as insoluble,
water-proof, highly ordered fiber
Mechanical properties due to molecular
structure
Extensive regions of crystalline
organization: protein sheet crystals
parallel to long axis of fiber
~ 50% protein between crystalline regions
is amorphous organic polymer matrix,
crucial in structure-property relationship
Reversibly transforms to contracted state when placed in polarsolvent
Production of synthetic silk requires complete understanding of structure-
property relationship of spider silk: gene sequence, protein structure,
mechanical properties, mechanism of silk spinning
Biomaterials:
Ferritins
Ferritinmolecule: self-assembled spherical
protein shell of 24 proteins
Outer diameter 12 nm, inner diameter 8 nm
Channels to allow iron ions to pass in and
out of structure
Storage, transport and detoxification of iron
Present in many types of living organisms;
from bacteria to mammals
Native protein cavity contains 6 nm
iron(III) oxyhydroxide(ferrihydrate) or
iron(III) phosphate nanoparticles
Protein shell prevents aggregation of
inorganic particles
Biocompatible, soluble reaction vessels for
creation of small particles of new
nanophasematerials with narrow size
distribution
Reductive dissolution to
give apoferritin:
demineralized, empty
protein cages
Chemical synthesis of new
materials in cage: 78Åironsulfide, 70Åmanganese
oxide, 60Åuranyl
oxyhydroxide
Modification of native
ferritincore viachemical
treatment
Vesicle Templating of Nanoparticles
Vesicles and liposomescan vary in diameter (1 to 500 nm)
Pt, Ag, CdS, ZnS, Fe
3O4, FeOOH, Al
2O3
Science1996, 271, 1267
Vesicle-templating of a
lamellar silica
TEOS + 1,12-diaminododecane
(DADD) + EtOH+ H
2O
Inorganic material growth in
the interlayer region of
multilamellarvesicle
Layers are pillared; material
can be calcined
High degree of thermal
stability and surface area
Tissue Engineering
Development of biological substitutes that restore, maintain, or
improve tissue or organ function (bone, cartilage, blood
vessels, bladder, skin, etc.)
Specific mechanical and structural properties for proper
function
Cells as building blocks:living cells as engineering materials,
e.g. fibroblasts in skin replacement or repair; cartilage repaired
with living chondrocytes
Scaffolds:cells implanted into an artificial porous structure
capable of supporting 3-D tissue formation
Allows cells to retain its biochemical factors
Provides structural integrity
Biocompatible or biodegradable
e.g. collagen, polyesters, polylacticacid,
macroporoushydrogels
Tissue Engineering
Organ farmingneeds more complex functionality and
biomechanical stability in tissues destined for transplantation
Convergence of engineering and basic research advances in
tissue, matrix, growth factor, stem cell, developmental biology,
bioinformatics and materials science
Organ of cadaver as template
Dissolve original cells, leave protein as a scaffold
Introduce cells, creates functional organ
No rejection, no drugs necessary to suppress
immune system
Hearts, lungs, liver, brain, bones, 
Perfusion-decellularizedmatrix: using nature's platform to engineer a bioartificialheart,
Nature Medicine 2008, 14, 213
Adv. Mater.1998, 10, 1185
Artificial Bone
Bones
Provide mechanical support, protection of soft
organs, blood production (from bone marrow)
Very complex, hierarchical tissue: strong,
elastic, and self-repairing
Autografts, allografts, xenografts, ceramics,
alloys: limited options and can be rejected
Artificial Bones
Synthesized using materials on or in which
bone tissue can adhere and grow
Bone powder, metal-ceramic composites,
rattan wood, stem cells, hydrogels,
osteoblasts& osteoclasts, 
Synthesis of
Inorganic Materials
with Complex Form
Nature1996, 382, 313
Water-alkane-DDAB
bicontinuousmicroemulsion
Synthesized at 2°C, oil is frozen
Replacement of water channels
with supersaturated Ca
3
(PO
4)2
solution
Hyrdoxyapatite, Ca
10
(OH)
2(PO
4)6
,
macroporousinorganic replica
Nature 1995, 378, 47
Macroscopic
morphologies of a
mesolamellar
aluminophosphate
Solvothermally-
templated,
inorganic
liquid crystal-
templated,
hierarchical
inorganic-organic
hybrid material
Synthesis of Inorganic Materials
with Complex Form