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MAT3430 > Material/Biological Interactions > Flashcards

Material/Biological Interactions Flashcards

1
Q

What are the potential causes of biomaterial failure?

A 
• Material
 – toxicology 
– surface properties and biointeractions 
– mechanical 
– biostability 
• Fabrication/Design 
• Surgery
 • Infection 
• Patient biochemistry and physiology 
• Patient compliance
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2
Q

How might cells in the body react to a biomaterial?

A
  • Inflammatory response
  • Immune response
  • Death (toxicity)
  • Sensitivity (allergic response)
  • Encapsulation – to protect body from objec
  • Cancer
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3
Q

What are the types of biocompatibility?

A
  • Bioinert
  • Biodegradeable
  • Bioresorbable
  • Bioactive
  • Biocompatible
  • ‘3rd generation’ Biomaterials
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4
Q

What is the definition of biocompatible?

A

Ability to be in contact with a living system without producing an adverse effect. (IUPAC)
Ability of a material to perform with an appropriate host response in a specific application (D. Williams and ESBiomat)

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5
Q

What are five examples of bioreactions?

A

protein adsorption macrophage adhesion protein retention phagocytosis lipid adsorption macrophage release bacterial adhesion neutrophil attachment
platelet adhesion biodegradation hemolysis angiogenesis platelet activation cell spreading expression of genes fibrous encapsulation

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6
Q

In an implant, what can the reaction be to?

A
  • Material itself
  • Residues form processing/ packaging/ sterilisation
  • Degradation products
  • Infection induced by/ carried on the biomaterial
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7
Q

What is the Sequence of host reactions following implantation of medical devices?

A
  • Injury
  • Blood-material interactions
  • Provisional matrix formation
  • Acute inflammation
  • Chronic inflammation
  • Granulation tissue
  • Foreign body reaction
  • Fibrosis/fibrous capsule development
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8
Q

What is the Summary of biomaterial reaction processes?

A

1) implantation
2) protein adsorption (>1 seconds)
3) cellular infiltration (60 minutes)
4) Release of cytokins and chemokines from cell (1-5 days)
5) recruitment of tissue repair cells (5-15 days)
6) fibrous encapsulation andd granulation tissue formation (3-4 weeks)

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9
Q

What cells does an acute response to a biomaterial involve?

A

neutrophils

leucocytes

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10
Q

What cells does an chronic response to a biomaterial involve?

A

macrophages

foreign body giant cells

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11
Q

What is the common immune response to biomaterials?

A 
innate immunity (i.e. not involving antibodies) 
although materials can be antigenic (allow antibody binding)
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12
Q

What is the complement system?

A

Small proteins found in the blood that when stimulated to break down initiate cytokine activity and innate immunity

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13
Q

What is the role of complement proteins?

A

make holes in pathogen membranes

recruit phagocyte

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14
Q

What are the two type of complement pathways?

A

classical pathway

alternative pathway

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15
Q

What is the early response of the body to a biomaterial?

A

involves complement

1) endothelial cell lining capillaries near injured site release enzymes
- plasma protein C2 changes conformation -> cleaved into fragments = C3b fragments
2) complement attacts neutrophils

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16
Q

What is the role of C3b?

A

1) attaches to biomaterial and when leucocytes migrate to the area they attach to the INSOLUBLE C3b, Immunoglobulins attach too
2) acts as a catalyst in the break down of c5 producing C5a which is a SOLUBLE ligand (binding protein) for leucocytes

17
Q

What is the role of C5a in the complement system?

A

can invoke adverse response to extracorpeal hemadialysis

18
Q

What happens when the complement attracts neutrophils?

A

neutrophils bind C51

  • associated with acute inflammatory response (minutes -> 1-2days)
  • become hyperadherent by increase CR3 (integrin CD11b/CD18) surface expression
  • attache to vasculature via endothelial ICAMs
  • chemotactic to C5a: migrate to inflammation site
19
Q

What is hyperadherent?

A

cells with adhere strongly

20
Q

What is chemotactic to C5a?

A

cells will migrate to the area attracted by the biochemicals

21
Q

How do foreign body giant cells evolve from macrophages?

A

monocyte -> macrophage -> giant cell

blood -> soft or hard tissue -> biomaterial/tissue interface -> biomaterial

22
Q

How does macrophage response depend on size of the material?

A

Large materials create ‘frustrated phagocytosis’

cannot engulf and digest - instead extracellular degradation

23
Q

What is encapsulation?

A

Nearly all biomaterials end up encapsulated by fibrous capsule

24
Q

What is the exception to encapsulation of biomaterials?

A

bone implants with good bone/implant interface and porous materials with cells include

25
Q

What happens if an immune reaction goes out of control?

A

allergy
allergen->antigen presenting cell-> Tcell -cytokines->Blymphocyte -IgE synthesis->plasma cell+unbound IgE -> Mast Cell+allergen = release of inflammatory mediators

26
Q

What is an allergen?

A

be protein that binds to the material not necessarily material itself

27
Q

Can implants cause tumours?

A

Yes but relatively rare
Associated with the fibrous foreign body tissue
The worse the inflammation reaction the higher the chance of tumour

28
Q

How can biomaterials encourage bacterial growth?

A

1) bacteria compete with cells to adhere to surface
- similar mechanisms: better adapted to nonviable surfaces
- resistant to antibiotics (different surface expression)

29
Q

What are the most common bacterial infections with which biomaterials?

A 
polymeric biomaterials (S.epidermis) 
metallic biomaterials (S.aureus)

have receptors for fibronectin and collagen

30
Q

How does a material enncourag Biofilm formation?

A

1) community of bacteria adherent to implant
2) very resistant to antibiotics
3) need to have bacteria-resistamt surfaces or localised delivery of antibiotics

31
Q

What are the ideal mechanical properties of a biomaterial?

A

want strong durable material but shielding cells form mechanical stimuli can cause cell death.

32
Q

What is the ideal surface roughness of a biomaterial?

A

roughness encourages bacteria and macrophages but also improves cell and tissue bonding to surface.

33
Q

What is the ideal Chemical composition of a biomaterial?

A

want the ‘right’ proteins to attach (adhesive/non adhesive?) antibacterial surface but not toxic to bodies own cells

MAT3430 (12 decks)

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