Lecture 8: Biocompatibility

Question 1

1. Give the definitions of Bioinert, bioresorbable, biocompatible and bioactive.

Answer 1

Bioinert materials are ones which do not initiate a response or interact when introduced to biological tissue. A Bioabsorbable polymer is a chemical compound used in orthopedic implant devices that eventually dissolves and is absorbed by the body. Biocompatibility with living tissue or a living system by not being toxic, injurious, or physiologically reactive and not causing immunological rejection. Bioactive produces a biological response.

Question 2

2. What do R and S phrases mean and what are they used for?

Answer 2

is a system of hazard codes and phrases for labeling dangerous chemicals and compounds.The R/S statement of a compound consists of a risk part (R) and a safety part (S), each followed by a combination of numbers.

Question 3

3. How does the NFPA work? What does a higher number mean?

Answer 3

The National Fire Association has developed

has developed a color-coded number system called NFPA 704.

Blue = health hazard

Yellow = stability

Flammability = red

number is more severe

Question 4

4. What do LD50 and LC50 mean? How are these numbers obtained?

Answer 4

LD50 = The dose required to kill 50% of cells

LC50 = The concentration required to kill 50% of cells.

Test on animals.

Question 5

5. Mention six factors that can control cell fate and describe how you could control this in an implant.

Answer 5

1. -> biocompatible (immunecompatible)
2. -> biodegradable (into nontoxic products)
3. -> stiffness - make it to match mechanical properties of the tissue
4. -> porosity
5. -> topography - surface
6. -> hydrophobic/hydrophilic - surfactant

Question 6

What is Simulated Body Fluid and how is this used to predict the success of implants? Specify what kind of implants you are talking about.

Answer 6

A simulated body fluid (SBF) is a solution with an ion concentration close to that of human blood plasma, kept under mild conditions of pH and identical physiological temperature.

SBF can be used as an in vitro testing method to study the formation of an apatite layer on the surface of implants so as to predict their in-vivo bone bioactivity.

Question 7

7. In general terms, explain how the Live/Dead cells double staining assay works and describer how it is used to evaluate biomaterials.

Answer 7

A mixture of two dyes, each of which stains different portions of a tissue or cell.

The live cells dyes are membrane permeant and fluoresce at a particular frequency.

The dead cell dyes are membrane impermeant and bind to DNA and flouresce at a different frequency.

Question 8

8. In general terms, explain how the MTT assay works and describe how it is used to evaluate biomaterials.

Answer 8

The MTT assay is a colorimetric assay for assessing cell adhesion, proliferation and cell metabolic activity.

Enzyme -> reflect the number of viable cells present

Question 9

How can a biomineralization assay be performed: in different cells; and in different materials?

Answer 9

-

Question 10

10. What is the meaning of: osteogenic, osteoconductive, osteoinductive?

Answer 10

osteogenic - relating to the formation of bone.

osteoconductive - guides bone formation

osteoinductive - induces bone formation

Question 11

11. What is the critical defect size and how is this used to evaluate bone implants?

Answer 11

the minimum size of a fracture that will still heal naturally.

Question 12

12. How would you test the osteogenic, osteoconductive, osteoinductive properties of a new biomaterial?

Answer 12

SEM - Osteogenic