L3 - Biomaterials

Question 1

What is a biomaterial?

Answer 1

Nonviable material used in a medical device, intended to interact with biological systems

Question 2

What can biomaterials be used for?

Answer 2

Development of scaffolds

Question 3

What is biocompatibility?

Answer 3

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

Question 4

What is an appropriate host response?

Answer 4

Resistance to blood clotting and bacterial colonisation and normal healing

Question 5

What is a polymer?

Answer 5

Large molecule made up of chains or rings of linked monomeric units

Question 6

What are hydrogels?

Answer 6

Crosslinked polymer networks that are insoluble but swellable in aqueous medium

Question 7

What are the benefits of hydrogels?

Answer 7

Offer an environment similar to the highly hydrated state of natural tissues

Question 8

What are the two classes of natural polymers?

Answer 8

Protein based: Collagen, gelatin, silk, fibrin, elastin and soybean
Polysaccharides: Chitosan, alginates, hyaluronan, chondroitin sulfate

Question 9

What are the pros and cons of natural polymers

Answer 9

P - naturally occurring therefore biofunctional

C - Batch-to-batch variability

Question 10

What are some common synthetic polymers and what pros/cons do they have?

Answer 10

Polylactic acid (PLA), polyglycolic acid (PGA) and poly(-lactic-co-glycolic) acid (PLGA)
Can be designed for a specific purpose but are costly and run the risk of rejection

Question 11

What is a semi-synthetic polymer?

Answer 11

Hybrid molecule made by incorp of biologically active molecule onto backbone of synthetic polymer
e.g. Semi-synthetic polyethylene-glycol (PEG)-fibrinogen
PEG: density, stiffness and biodegradability
Fib: presents biofunctional domains

Question 12

Natural vs Synthetic

Answer 12

Natural:
Built in bioactivity BUT purification, cost, immunity, lack of mechanical properties, batch variations

Synthetic:
Controlled mechanical properties and degradation, easy processibility, minimal batch variation BUT difficult to predict biocompatibility

Question 13

What are the properties of biomaterials?

Answer 13

Physical/mechanical - strength, elasticity and architecture
Chemical: degrad, resorption, water content
Biological: interactions with cells, release of materials

Question 14

Bulk properties of biomaterials

Answer 14

Strength, toughness, fatigue resistance, stability

Question 15

What are surface modifications?

Answer 15

Overcoating biomaterial with molecules of different properties to optimise function

Question 16

Do cells directly interact with the material?

Answer 16

No, a layer of protein (from plasma or growth media) adheres to the surface and the cells interact with this. The surface properties of the material affect what proteins are absorbed

Question 17

What is a non-fouling material?

Answer 17

Resistant to ab of pt therefore won’t adhere to cells
PEG and zwitterionic polymers
May inhib bact colonisation in medical devices

Question 18

How to cells adhere?

Answer 18

Through the receptors in their membrane

Question 19

How do cell responses vary?

Answer 19

The surface density of RGD peptides immobilised can vary which changes the cell response

Question 20

How are surfaces functionalised?

Answer 20

• Attach biomolecule to polymer

- Immobilization of integrin-binding peptides or entire protein

Question 21

Explain the study - Geometric control of cell life and death (Chen et al)

Answer 21

Background - angiogen relies of interplay of mech and chem signals. Endo cell growth is critical to angio. Increase in endo spread area accompanied by an increase in cell proliferation
HYPOTHESIS - cell shape controls cell fate in endo cells
Approach - micropatterning of fibronectin islands - cells assume shape of island
Results - extent of spreading determined whether cell underwent prolif or apop
Cells can filter the same set of chemical inputs to produce different functional outputs

Question 22

Explain the study - Shape-mediated differentiation of MSCs

Answer 22

RQ: Do changes in cell shape regulate commitment of SC to different lineages?
MSCs on islands of different shapes
Results - Flattened, spread cells = osteogenic lineage. Unspread, rounded cells commit to adipogenic lineage