BME213 Sem 1 & 2 Flashcards
Define Biomaterials
A material intended to interface with biological systems to evaluate, treat, augment or replace any tissue, organ or function of the body
What are the 6 requirements for implantable biomaterial?
- Non-toxic
- Non-carcinogenic
- Non-allergic
- Non-inflammatory
- Biocompatible
- Biofunctional for its lifetime
What is In vitro testing?
Means within a glass, observable in a test tube.
Yields important fundamental information about certain elements of cellular and molecular interactions with biomaterials
What is in-vivo testing?
Means within the living body
Assessment is based on the cumulative physiological response of the tissue to the biomaterial
– Complex wound healing process
– Chronic inflammation response
– Modelling of surrounding tissue
– Blood-material interaction.Official
What are the phases of wound healing?
- Coagulation
- Inflammation
- Proliferation
- Repair and Remodelling
Describe coagulation in wound healing
When injury occur, there’s a loss in structural integrity of the tissue and disruption to the blood vessel network. Hence, coagulation is triggered to prevent bleeding.
Damaged tissues release a pound called THROMBIN into the blood stream
This compound catalyses the conversion of soluble fibrinogen to insoluble fibrin which forms a matrix to trap platelets and many vasoactive and chemotactic factors
Trapped aggregate of platelets secrete various mediators of wound healing and facilitate further processes such as cellular attachment and clot formation
Ability to form clot -> impt to stop local bleeding : failure may lead to excessive blood loss
When an implant is added, what does the body experience?
- “Dead space” surrounding the implant
- Soluble agents released by the implant (eg ions, polymer fragments)
- Insoluble particulate material released from the material (wear debris)
- Chemical interactions of biological molecules with the implant interface
- Alterations in the strain distribution in tissue
Explain the inflammation phase of wound healing
Characterised by the release of various mediators to the injured site
Involves the (excessive flows )exudation of fluid and plasma proteins to increase the dilation and permeability of the vessel wall. This in turn facilitates the rapid influx of more mediators
Also involves the immigration of cells such as neutrophils, macrophages and foreign body giant cells to the affected site
The warm, swelling and tenderness of the injured tissue after a fall or sprain is the physical symptoms of inflammation
Neutrophils are the predominant cell types present in an acute inflammation and play a vital role in the wound healing process
Neutrophils are unable to regenerate their enzymes and decay after phagocytosis, Hence the introduction of macrophages cells is important in the initial wound healing phase
Macrophages cells are bigger, live longer, and capable of regenerating enzymes to continuously degrade and remove damaged and dead tissues components (including dead neutrophils) from the injured site
– Macrophages are the characteristic cells of chronic inflammation
What is foreign body reaction?
Biomaterial or implant is much bigger than the cells, the macrophages are unable to fully engulf it for phagocytosis.
In turn, they fuse and combine to form foreign body giant cells at the implant-tissue interface
This phenomena is commonly known as the foreign body reaction
Describe the proliferation phase of wound healing.
Proliferation refers to the growth and multiplication of new cells
In wound healing, it is stimulated by multiple growth factors released in the inflammation phase and main aim is to repair or replace the damaged tissue
Proliferation produces granulation tissue which comprises:
*A loose matrix of: fibrin (predominately)/ collagen/elastin
*Containing: macrophages/ fibroblasts/ in-growing blood vessels
– In deep wounds, where there is extensive loss of cells, this granulation tissue serves as a temporary matrix allowing in-growth of new tissues
What kind of bonding is found in metals, and how does it affect their properties?
Metallic bonding (delocalized electrons around metal ions).
This results in high electrical and thermal conductivity, ductility, malleability, luster, and moderate to high melting points.
List 3 important mechanical properties. Give examples why these properties are important with relations to an application.
- Strength – Ability to withstand forces without breaking.
• Example: Steel in bridges must support heavy loads without deforming. - Toughness – Ability to absorb energy and deform without fracturing.
• Example: Car bumpers absorb impact during collisions to protect passengers. - Hardness – Resistance to surface deformation or wear.
• Example: Cutting tools need hardness to maintain sharp edges and resist wear.
How does grain structure affect mechanical property of a metal?
Grain structure influences strength, hardness, and ductility:
• Smaller grains (fine-grained structure): Increase strength and hardness (due to grain boundary strengthening) but reduce ductility.
• Larger grains (coarse-grained structure): Improve ductility but reduce strength.
• Grain boundaries act as barriers to dislocation movement, which strengthens the metal (Hall-Petch relationship).
Example: Cold-worked or heat-treated metals with refined grains are stronger and more wear-resistant.
What kind of bonding is found in ceramics, and how does it affect their properties?
Ionic and/or covalent bonding.
These strong, directional bonds make ceramics hard, brittle, electrically insulating, chemically resistant, and capable of withstanding high temperatures.
What kind of bonding is found in polymers, and how does it affect their properties?
Covalent bonds within chains and weak van der Waals or hydrogen bonds between chains. This gives polymers low density, flexibility, low melting points, electrical insulation, and thermal sensitivity.
What kind of bonding is found in composites, and how does it affect their properties?
Mixed bonding depending on the materials used (e.g., polymer matrix + ceramic or metal fibers).
This enables customized properties like high strength-to-weight ratio, improved toughness, and durability for specific applications.
Describe the 3 processes of proliferation
Proliferation consists of three simultaneous processes
• Matrix production
• Angiogenesis
• Epithelization
Proliferation (Matrix production)
– Fibroblasts first migrate to the affected site and are activated to produce large amounts of fibrin. The fibrin combines with other protein components such as collagen and elastic to form the loose matrix
– As the fibroblasts are aligned to the wound axis, cell-to-cell links are formed which contribute to the contraction of the wound. This also gives the wound
its early form.
Proliferation (Angiogenesis)
– Angiogenesis is the growth of new blood vessel
– The disruption of blood vessel network resulted in low oxygen content and low pH at the injured site.
These are believed to be the main stimulus to angiogenesis
– The growth of vessel starts from capillary buds sprouting from blood vessels adjacent to the wound and extend into the wound space. This is an important process to restore normal blood flow to the
affected tissue
Proliferation (Epithelization)
– Epithelization involves the migration of epithelia cells from edges of the wound to proliferate in the wound site, thereby closing the wound
