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Materials in medicine > Sean frågor > Flashcards

Sean frågor Flashcards

1
Q

What is a parenchymal cell?

A

The cells that make up our organs and have very specific functions

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2
Q

Explain cell regeneration and repair versus fibrosis.

A

Regeneration: Parenchymal cell death with intact tissue. Restored to normal function.

Repair: Parenchymal cell death with damaged tissue. Scar formation.

Fibrosis: Causes tissue scarring. With long-term liver inflammation, excess fibrous connective tissue thickens the tissue cell walls and lead to reduced O2 supply

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3
Q

Describe ESCA as well as advantages , disadvantages and areas of application

A

X-rays are directed at a sample which causes the electrons on the surface to emit in a certain pattern that can be analysed to determine the compunds composition. Measures the binding energy of the compunds electrons.

+Surface sensitive, high resolution
-Elemental limitations, expensive, need for strong vacuum chamber

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4
Q

Describe FCC structure

A

Close packed. ABC|ABC|…. Each corner has a fraction of an atom and each side has the center of an atom. Metals.

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5
Q

Describe HCP structure

A

7-3-7 layered unit. Metals and large molecules

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6
Q

Describe BCC structure

A

One atom in middle, fraction of atoms in every corner. Metals.

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7
Q

Descibe diamond structure

A

FCC but with a 4 extra atoms connected in the middle kinda. Si, C, Ge…

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8
Q

What are the three generations of biomaterials?

A

First generation: Bio-inert materials, orthodpedic implants and dental materials

Second generation: Bio-active materials. Drug delivery and resorbable.

Third generation: Regenerative materials. Biomimicking and degradable.

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9
Q

What is biocompatibility

A

A materials ability to perform a certain task in the body and induce an appropriate host response.

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10
Q

Describe the biocompatibility pathway.

A

Biomaterial and host come in contact –> Initiation of host response –> Progression of host response –> Indaequate resolution (not tolerable) OR resolution of response (tolerable)

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11
Q

What are the main classes of materials used in the body, name their properties.

A

Polymers - Elastic, easy to produce
Natural materials (proteins, polysaccharides) - bioactivity, may resorb
Metals - Strong, ductile, may corrode
Ceramics - Biocompatible in bone, brittle
Composites - Strong, hard to make

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12
Q

What is nominal stress?

A

Force applied orthagonal to the cross sectional area of a sample (N/m2 or Pa). Tensile if elongating, compressive if shortening

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13
Q

What is nominal strain?

A

A measure of deformation as a result of stress

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14
Q

Describe each area of the stress-strain curve for
1. Titanium alloy
2. Al2O3
3. High Density Polyethylene

A

Kolla L4

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15
Q

Difference between resilience and toughness.

A

Resilience: Elastic energy that can be stored in a unit of stressed material

Toughness: Energy required to deform a unit volume of material to its breaking point. Hip implant

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16
Q

What is UTS?

A

Ultimate Tensile Strength. Maximal stress shown in the stress strain curve.

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17
Q

What is ductility?

A

Formability of a material. All biomaterials

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18
Q

What difference is there between the true and the engineered stress-strain curve?

A

True stress and strain can be obtained by scaling the applied force with reference to the actual cross-sectional area of the sample

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19
Q

What is hardness?

A

How successfully a material resist plastic deformation. Dental materials

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20
Q

What is the poisson ratio?

A

Deformation relation. Tensile stress –> Elongation and thinnification

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21
Q

What is an isotropic material?

A

Structure and properties do not vary with direction.

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22
Q

What is an anisotropic material?

A

Structure and property measurements depend on which direction the load is applied to the sample. Biological materials are most often anisotropic.

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23
Q

Explain tensile testing

A

Tests a material by acting upon it with a force and looking at properties such as toughness or resilience.

24
Q

Explain wettability and youngs equation

A

Wettability: Ability of a liquid to establish contact with a surface

Young’s equation: Ysv=Ssl+Ylv*cos(v). Ysv is interfacial tension between surface and air.

25
Q

Explain ESCA/XPS and SEM

A

ESCA/XPS: Measure binding energy. Material emits electron cause of x-ray bombing

SEM: Electron gun nips of electrons of material. Scatter plot for elemental identification. Magnifies surface millions of times.

26
Q

Name the properties which metals excel at

A

High strength, young’s modulus similar to bone, fatigue properties

27
Q

Give examples of use of metals in medicine

A

Stainless steel in bone implants, titanium screws and dental implants.

28
Q

What is fatigue? How is it measured?

A

Structrual damage that grows over time. Starts with a small nick and gets progressivly worse. Occurs without plastic deformation (no warning). Measured using rotating cantilever beam test.

29
Q

Describe the difference between a stress-strain curve of a metal, ceramic, and polymer

A

Metal: Normal curve
Ceramic: High Youngs modulus, no deformation before fracture (straight line)
Polymer: Very high youngs modulus, followed by a drop and then flatten out before fracture.

30
Q

What are the five requirements for biometals?

A
  1. Stronger than bone
  2. Modulus close to bone (avoids stress-shielding)
  3. High strength
  4. Biocompatibility
  5. Price
31
Q

Describe the strength and youngs modulus for bone to titanium and cobalt-chromium

A

Tensile strength is much higher for the metals but the E-modulus is too high for the metals.

32
Q

Name one drawback for titanium, cobalt-chromium and stainless steel

A

Ti: Poor friction qualities
Cobalt-chromium: Prone to fatigue
Stainless steel: Moderate corrosion resistance

33
Q

Name and explain the 6 types of corrosion

A
  1. Pitting (localized corrosion)
  2. Stress-corrosion cracking (mechanical stress+corrosive environment)
  3. Intergranular (mass lost–> mech. properties reduced
  4. Crevice (deposite attack)
  5. Galvanic (direct contact with liquid)
  6. Fretting corrosion
34
Q

What environmental factors cause corrosion?

A

High oxygen, hydrogen, metallic inert ions. Presence of salt.

35
Q

In which 4 ways can we avoid corrosion?

A
  1. Materials selection
  2. Coating
  3. Avoid design with dissimilar metals in contact
  4. Environmental control. (different parts of the body are different environments)
36
Q

What are the advantages of titanium in bioapplications?

A

High reactivity –> protective oxide layer. Inertness. Mechanical properties.

37
Q

Describe the three main types of biomaterial infections.

A

Superficial immediate infections - bacteria
Deep immediate infections - After invasive surgery
Deep late infections - months after surgery, bacteria in body colonizing implant

38
Q

What is sepsis and what are symptoms?

A

Blood poisoning. Fever, rapid heart rate, sweating

39
Q

How do we prevent biomaterial associated infections using antibiotics?

A

Coating or make the biomaterial drug releasing.

40
Q

What are the 4 steps of biofilm?

A

Attachment –> expansion –> maturation –> detachment

41
Q

What does the EPS contain?

A

Extracellular DNA, polysaccharides, lipids, proteins

42
Q

Why are biofilms so hard to eradicate?

A

Bacteria dormant, as well as antibiotics reacting with the EPS

43
Q

Describe the gram negative and positive cell walls

A

Negative: Inner and outer lipid membranes
Positive: Inner lipid membrane and outer shell of peptidoglycans

44
Q

What are some strategies to prevent biofilms?

A

Non-adhesive surface, tissue integrating surface

45
Q

What are the 3 types of polymers?

A
  1. Thermoplastic: Deformable upon heating, can be melted repeatedly
  2. Thermoset: Hard and rigid upon heating. Cannot be melted
  3. Elastomers: Stretchy. Cross linked polymers
46
Q

Describe the following hydrogels and their properties:
1. chitosan 2.agarose 3.alginate 4.hyaluronic acid 5.gelatin 6.PAA 7.phema

A
  1. From crustaceans. Swelling and bioadhesive
  2. From seaweed. Used in pharmaceutical capsules
  3. From algae. Used in food
  4. From rooster comb. Cosmetic and biomedical
  5. Is a protein. Capsules. Dissolves in body
  6. Inert. Insoluable. Not absorbed
  7. Inert. Not absorbed. Withstand sterilization
47
Q

What are the 5 uses of hydrogels?

A

Implant coatings, catheter coatings, tissue engineering, wound dressing, contact lenses

48
Q

What is a gel?

A

Cotains solvents (hydrogel-water). Contains compund that is swollen and crosslinked with solvent, usually polymer.

49
Q

What are the advantages and disadvantages of hydrogels?

A

+Biocompatible, shapes itself after its site, biodegradable if needed
-Loading capacity, low tensile strength

50
Q

What are the 3 classifications of hydrogels?

A

Crosslink, charges, structure

51
Q

What is a smart gel?

A

A gel that swells up after activation by a specific action by the body

52
Q

How do we characterize gel functions?

A

Swelling, mechanical properties, rheology, diffusion, microscopy

53
Q

What are the 5 types of degradable polymer implants?

A
  1. Temporary support device
  2. Temporary barrier
  3. drug delivery device
  4. Tissue-engineering scaffold
  5. multi-functional implant
54
Q

Explain the properties of surface and bulk erosion.

A

Surface: mass loss is faster than the entering of water in the bulk. Bulk and core remains intact

Bulk: Water enters quicker than the rate of degradation. Occurs throughout material, causing uniform degradation

55
Q

What is sterility assurance level (SAL)?

A

Probability that a given implant will remain nonsterile after sterilization. Minum for implants is 10^-6

Materials in medicine (4 decks)

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