Lecture 4/5 Slide Deck Flashcards
What are the Classes of Biomaterials?
- Polymers - Long Chain Molecules; synthetic or natural
- Composites - Combinations of Different Materials
- Ceramics - Clay, Cement, Glass; Insulating; often hard and brittle
- Metals - Large numbers of non-localized electrons; good conductors, non-transparent; strong but deformable
What condition does protein fold change with?
Temperature
A biomaterial must fulfill specific requirements relevant to its use, what are these 4 considerations?
- Physical and Chemical Properties
- Biocompatibility Properties
- Serializability
- Manufacturing Properties
What are some Chemical and Physical Properties?
Strength, Toughness, Elasticity, Flexibility, Wear, and Stability
What are some Biocompatibility Properties?
Anti-thrombotic, nontoxic, nonallergenic, non-inflammatory
Why is Sterilizability important?
Stability under sterilization conditions is important for prevention of disease and infection
What are some Manufacturing Properties?
Ease of shaping, machining, moulding, extruding, melting, reproducibly (Availability or Scale-Up)
What are some characterization techniques?
-XRD
-FTIR
-UVs/VIs
-NMR
-AFM
Where does In-Vitro testing occur?
Outside system/body
Where does In-Vivo testing occur?
Inside system/body
What is the structure of metals?
Consist of positive ions arranged in an array within a sea of delocalized electrons
What do metals undergo to improve their properties?
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
What are 2 typical failures of metallic materials
- Mechanical failures (bulk issue)
- Chemical breakdown (corrosion, etc)
What determines metal structure?
Annealing (cooling from melt state) and doping (addition of alloying elements) determine the grain size, crystal packing, grain orientation and boundaries
What are the advantages of metals?
- Very high strength, fracture resistance, load-bearing capability, and toughness
- Ductile and are easy to shape
- Generally biocompatible but still need to be modified
What are some disadvantages of metals?
- 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
- Not interplay between metal and native tissues
- Susceptibility to corrosion
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?
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
How can galvanic corrosion be prevented?
Selecting materials with similar corrosion potentials, and applying a coating to both materials
What is a major limitation with current assessments of corrosion in metallic medical devices?
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
