Week 11 Flashcards
materials found in biological systems (e.g., nature) that could be used in biomedical applications
natural biomaterials
What are two examples of natural biomaterials?
- jade stones –> replace tooth
- coral –> bone graft
What are the 4 advantages of natural biomaterials?
- cell attachment
- enhance mechanical properties of synthetic biomaterials
- bind and deliver macromolecules
- improved biocompatibility
What are 3 disadvantages of natural biomaterials?
- increased immunogenic
- structural complexity
- degraded by enzymes
What are 3 applications of natural biomaterials?
- tissue engineering
- regenerative medicine
- wound healing
- antibacterial coatings - medical devices
- bioprosthetic implants
- heart valves
Natural biomaterials can mimic the properties of what two materials?
- polymers
- ceramics
What are 5 examples of protein-based natural biomaterials?
- collagen
- gelatin
- silk fibroin
- fibrin
- elastin
What are 7 examples of polysaccharide-based natural biomaterials?
- chitosan
- starch
- alginate
- hyaluronan
- chondroitin
- sulfate
- dextran
This type of natural biomaterial is a protein that is exclusively found in animals and is the most abundant protein in the human body
collagen
What is collagen a part of?
extracellular matrix
What is the main function of collagen?
provide structural support for connective tissues
What are the two primary features of collagen?
- act as glue connecting tissues
- strength and structural integrity
What is the primary protein of the skin?
collagen
Collagen is a type of connective tissue found in what 4 parts of the body?
- bone
- dentin
- tendon
- ligaments
Collagen makes up ___% of muscle tissue
1-2%
How many different types of collagen have been identified?
28
Each different molecular type of collagen is unique in what 4 ways?
- composition
- structure
- function
- tissue specificity
What are the two major types of collagen which make up 90% of the collagen in the body?
- Type I
- Type V
What type of collagen is found in dentin?
Type I
Describe the hierarchy of collagen
amino acids –> expand and grow and form helices –> tropocollagen –> crosslinking –> fibrils –> multiply fibrils –> fibers
What is the primary function of cross-linking?
side-by-side packing of fibrils to increase strength
What happens if cross-linking is inhibited?
tensile strength is drastically reduced
What happens to the amount of cross-linking as you age?
it increases
Describe the mechanical response of collagen
this is what the trend will look like if you apply a stress to break the collagen fiber
“toe region” –> tangled and you begin to stretch it
“linear region” –> collagen fibers are all in a line with eachother
“failure” –> collapse
What is the most abundant type of collagen in the human body?
type I
What type of collagen is the predominant form used in biomaterials application?
type I
Where are 8 places type I collagen is found?
- skin
- dentin
- cornea
- blood vessels
- bone
- tendon
- ligament
- fibrocartilage
What does type I collagen aggregate into?
fibrils
What does the diameter of type I collagen depend on?
- age
- tissue
(50 nm - 500 nm)
Describe type I collagen in teeth
forms a dense network array of individual thin fibrils, with an interfibrillar matrix
type II collagen
Where is type 2 collagen found?
articular cartilage
What 4 things is type II collagen made of?
- proteoglycans
- glycoprteins
- non-collagenous proteins
- water
What two things does the fibrillar network of type II allow?
- cartilage to entrap proteoglycan aggregate
- provide tensile strength to tissue
Another name for type II collagen
cartilage
This type of collagen is composed of 3 identical peptide a-chains (homotrimer)
type III collagen
What does type III collagen resemble?
other fibrillar collagens in structure and function
Describe the proteins in type III collagen
long, inflexible, triple-helical domain
Type III collagen accounts for ___ of collagen in adult skin
20%
Where is type III collagen found?
- skin of newborns
- blood vessels
- ligaments and internal organs
Where is type IV collagen found?
- eye lens
- blood vessels
- kidneys
- basal lamina
Describe the overall arrangement of type IV collagen
sloppy with kinks
True or false: Type IV collagen does not form fibril or fibers
True
What does Type IV collagen form?
meshes or networks which filter cells, molecules and light
Compare the 4 types of collagen
Where is collagen isolated from?
- animals
- bovine
- equine
- porcine - human
- cadaver
- placentas
Collagen is found in combination with what 3 things?
- growth factors
- silicones
- fibroblasts
What 3 forms are collagen found as?
- meshes
- gels
- mats
Collagen is ideally found without tissues or cells, also known as
contamination
What are collagen scaffolds used for?
bone regeneration and tissue enginering
What are collagen scaffolds often mixed with to improve performance?
hydroxyapetite
Describe 4 biomedical applications of collagen
This is a type of connective tissue protein with rubber-like properties
elastin
Natural elastin is (soluble/insoluble) extracellular matrix
insoluble
Where is elastin found (5 places)?
- skin
- bladder
- lungs
- arteries
- invertebral discs
What 3 things are of major importance in elastin?
- elasticity
- flexibility
- strength
The structure of elastin is primarily compose of
small non-polar amino acid residues
- glycine, valine, alanine, proline
In elastin, the interchain crosslinks form
desmosine residues
What kind of coil confirmation does elastin posess?
irregular
Elastin fibers consist of an albuminoid protein called
elastin
What are two properties of elastin fibers?
- pliable
- elastic
Elastin fibers can be stretched to ___% of their original length without breaking and then return to its original state
150%
Compare collagen and elastin
collagen dominated tissue will behave more like a ceramic (more stiff)
elastin dominated is more soft and will get really elongated
What are the 3 properties of elastin?
- insoluble due to crosslinks
- hydrophobic due to amino acids (75%)
- resistant to enzymatic, chemical, and physical degredation
Cross-links in elastin can be modified to do what 3 things?
- prevent mineralization
- promote cell adhesion and growth
- control degradation rate
How much elastin is in the lung?
30%
How much elastin is in the skin?
3%
How much elastin is in ligaments and arteries?
50-70%
Flexibility allows the organs to undergo what 3 things?
- strain and deformation without rupture
- store energy from deformation
- recover when stress is removed
What are the biomedical applications of elastin?
What are the monomers of chitosan?
monosaccharides
What is chitosan derived from?
chitin
Where is chitin found?
- cell walls of fungi
- cuticles of insects
- exoskeletons of shellfish
This is made up of a long linear polymeric chain of N-acetyl-d-glucosamine
chitin
How is chitosan formed from chitin?
deacetylation (remove acetyl group)
removal of acetyl functional group from chitin with hydroxides and high temperature
deacetylation
What 3 things does the removal of the acetyl from the glucosamine allow?
- tighter packing
- increase crystallinity
- solubility (DDA>50%)
What are the 4 favourable properties of chitosan?
- minimal foreign body reaction
- dissolves in water
- available side groups can attach to molecules (i.e., growth factors)
- mechanical and biodegredation controllable through polymer length, porposity, and DDA
What are the 5 features of chitosan?
What is commercial chitosan used for?
- repair focal cartilage lesions
- wound dressing for blood loss
a family of non-branched anionic polysaccharide copolymers that are derived from psuedomonas and axotobacter bacteria
alginate
True or false: alginate can be found in marine algae such as brown seaweed
true
What are two other names for alginate?
- alginic acid
- algin
What are the 2 alginate monomers?
What are the favourable properties of alginate?
In alginates, which residues can undergo acetylation? Which can’t?
acetylation - mannuronic acid residues
no acetylation - guluronic residues
What is the range of solutions for alginates?
slimy and viscous
Describe alginate impression material