Lecture 4/5 Slide Deck

Question 1

What are the Classes of Biomaterials?

Answer 1

1. Polymers - Long Chain Molecules; synthetic or natural
2. Composites - Combinations of Different Materials
3. Ceramics - Clay, Cement, Glass; Insulating; often hard and brittle
4. Metals - Large numbers of non-localized electrons; good conductors, non-transparent; strong but deformable

Question 2

What condition does protein fold change with?

Answer 2

Temperature

Question 3

A biomaterial must fulfill specific requirements relevant to its use, what are these 4 considerations?

Answer 3

1. Physical and Chemical Properties
2. Biocompatibility Properties
3. Serializability
4. Manufacturing Properties

Question 4

What are some Chemical and Physical Properties?

Answer 4

Strength, Toughness, Elasticity, Flexibility, Wear, and Stability

Question 5

What are some Biocompatibility Properties?

Answer 5

Anti-thrombotic, nontoxic, nonallergenic, non-inflammatory

Question 6

Why is Sterilizability important?

Answer 6

Stability under sterilization conditions is important for prevention of disease and infection

Question 7

What are some Manufacturing Properties?

Answer 7

Ease of shaping, machining, moulding, extruding, melting, reproducibly (Availability or Scale-Up)

Question 8

What are some characterization techniques?

Answer 8

-XRD
-FTIR
-UVs/VIs
-NMR
-AFM

Question 9

Where does In-Vitro testing occur?

Answer 9

Outside system/body

Question 10

Where does In-Vivo testing occur?

Answer 10

Inside system/body

Question 11

What is the structure of metals?

Answer 11

Consist of positive ions arranged in an array within a sea of delocalized electrons

Question 12

What do metals undergo to improve their properties?

Answer 12

They are alloyed to improve their overall properties.

Alloys are combinations of one or two more elements in a homogeneous phase resulting in a material with metallic properties

Question 13

What are 2 typical failures of metallic materials

Answer 13

1. Mechanical failures (bulk issue)
2. Chemical breakdown (corrosion, etc)

Question 14

What determines metal structure?

Answer 14

Annealing (cooling from melt state) and doping (addition of alloying elements) determine the grain size, crystal packing, grain orientation and boundaries

Question 15

What are the advantages of metals?

Answer 15

1. Very high strength, fracture resistance, load-bearing capability, and toughness
2. Ductile and are easy to shape
3. Generally biocompatible but still need to be modified

Question 16

What are some disadvantages of metals?

Answer 16

1. Potential for stress shielding, occurs when a stiffer material resists applied loads and buffers or “shields” surrounding tissue from these forces 2. Stresses borne by metallic implants instead of native bone lead to loss of bone density
2. Not interplay between metal and native tissues
3. Susceptibility to corrosion

Question 17

Combinations of metals corrode via galvanic corrosion - dissimilar metal corrosion; are electrically connected in the presence of an electrolyte where the anode will corrode faster than the cathode

What is an important factor that would impact galvanic corrosion?

Answer 17

The ratio of the exposed area of the cathode to the exposed area of the cathode, a small anode-to-cathode ratio is highly undesirable

Question 18

How can galvanic corrosion be prevented?

Answer 18

Selecting materials with similar corrosion potentials, and applying a coating to both materials

Question 19

What is a major limitation with current assessments of corrosion in metallic medical devices?

Answer 19

Lack of correlation between in-vitro and in-vivo corrosion performance

Different electrolyte composition of different oxygen concentration can induce flow of a galvanic current (through the electrolyte solution) in a metallic biomaterial