Biomaterials

Question 1

Biomaterials - definition?

Answer 1

Non viable minerals used in medical device, intended to interact with biological systems

Question 2

What is the main problem with regards to biomaterials?

Answer 2

Rejection

Question 3

What is meant by biocompatibility?

What can be included in the aspects of a ‘good host response’?

Answer 3

Ability of a material to perform an appropriate host response to a specific application

• Resistance to clotting - Normal healing - Resistance to bacterial colonisation

Question 4

What first brought about the need for biomaterials?

Answer 4

CATARACTS - natural clouding of the optic lense –> suggested need for a synthetic substance to be implanted without an immune response

Question 5

How did the field evolve (1, 2 and 3rd generations)

Answer 5

1st gen materials - bioinertness
2nd - bioactive material
3rd - functional tissues!!! Meaning these were stable, non-toxic and non carcinogenic

Question 6

What was the first material to be succesful biomaterial?

Answer 6

Bioglass –> 1st material to bond seamlessly to bone

Question 7

What are polymers, providing common examples?

Answer 7

Large macromolecules made of linked monomeric units. Minimum 200,000 units, can be linear or branched, joined by single C-C bonds

Question 8

Arrangements of polymers - what are the different arrangements and different ways they are structured? Why is this important?

Answer 8

Homopolymer – one type of monomer
Copolymer - more than one type of monomer makes up polymer
The arrangement of monomers in a polymer determines the material properties

Alternating copolymer: ABABABABABAB
Block copolymer: AAABBBAAABBB

Question 9

What are the basic classes of polymer?

Answer 9

Natural - derived from nature
Synthetic - manmande
Semi-synthetic - a mixture of the two

Question 10

NATURAL POLYMER - examples?

Answer 10

Protein-based - fibrin, elastin, soybean, silk, collagen

Polysaccharides - hyalauronan, chondriotin sulfate

Question 11

SYNTHETIC POLYMER - examples?

Answer 11

Polylactic acid

Polyglycolic acid

Question 12

Semi-synthetic polymer - example?

WHat is the structural layout of these molecules

Answer 12

PEG - polyethylene glycol-fibrinogen

Synthetic monomer backbone with biologically active macromolecules

Question 13

What are the biological, chemical and physical properties of biomaterials?

Answer 13

Biological - cell interactions, release of biologically active signals
Chemical - degradability, h20 content, resorption
Physical/mechanical - influence of cell behaviour, elasticity of cells, strength

Question 14

What is meant by degradable materials and why can this be a problem?

Answer 14

Molecules can be hydrolysed and water produced, meaning the polymer is breakable.
Problem is that the smaller molecules produced in hydrolysis may be TOXIC

Question 15

What are the bulk properties of biomaterials?

Answer 15

Strength, stability, resistance to fatigue, stiffness, surface properties (important for cell-cell interactions)

Question 16

What is meant by resorbable materials?

Answer 16

Materials that are metabolisable (no trace of them is left) and can be eliminated from the body

Question 17

What surface modifications can be made and what properties do they need to have?

Answer 17

Overcoating –> used to cover exisiting material to create surface patterning and texture
Allows chemical or physical alterations to atoms or molecules on the cell surface
The layer must be thin, resistant to delamination and lysable

Question 18

What is a non-fouling surface?

Answer 18

Resistant to adhesion or adsorbtion by other proteins
These can be used to inhibit bacterial colonisation on a material.
PEG is an example of this

Question 19

How do cell interactions occur and what does this allow?

Answer 19

Occur via receptors in the cell membrane via RGD domains of integrins (eg fibronectin)&raquo_space; allow cellular responses to vary

Question 20

What is micrometer scale chemical patterning and why is it done?

Answer 20

Created using microstamping and microcontact printing, allows production of a patterned substrate

Question 21

Angiogenesis –> how does this process show how cell properties can determine cell fate? How was this demonstrated?

Answer 21

Angiogenesis relies on chemical and mechanical signals

• Growth of the ECM in this case is important –> increase in spread of this causes an increase in cell proliferation
• Cells grown under the same conditions but with a different cell geometry caused a variation in apoptosis and proliferation

Question 22

In an attempt to recapitulate early embryonic development (using human embryonic stem cells), what was the effect of changing cell topography?

Answer 22

Changed the cell fate –> by altering topography, you are changing the arrangement of cells post-gastrulation, which determines the cell fate