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Flashcards in Exam 1 Deck (53):
1

Mn, Mw, and PDI, what is PDI=1 mean

Mw = Weight Average molecular weight
Mn = Number average molecular weight
PDI = Mw/Mn
If PDI = 1 --> Similar length chains

2

Atactic vs. Isotactic vs. Syndiotactic

Atactic = no order = Amorphous
Isotactic = one side = partial crystalline
Syndiotactic = alternating = partial crystalline

3

Addition polymerization

Addition of mer (repeated units)
Initiation with radical species, elongation/propagation, and termination

4

Condensation polymerization involves:

Elimination of certain byproducts (usually water) as a part of the synthesis reaction

5

Yield Stress vs. Fracture Stress vs. Ultimate Stress

Yield stress = max stress in the ELASTIC region
Fracture stress = Max load at failure
Ultimate stress = max load before necking occurs (absolute max)

6

PXRD peak sizes narrow vs wide

Amorphous = Wide smooth peaks, smaller crystal size, more noise

Crystalline = narrow peaks, larger crystal size, less noise

7

Ceramics have what qualities

High compression modulus, low ductility

8

Calcium Phosphate and HA make up _____ in body

Inorganic bone -- (not ligaments)

9

HA in human body is (high/low) crystallinity
(high/low) crystallinity is more easily absorbed

Low, Low

Low Crystallinity HA is more easily absorbed

10

Galvanic Corrosion can occur (not exclusively) when:

Two different metals of DIFFERING potential are placed near each other

11

Pitting

Passivation layer is removed, leads to ion loss at the site of pitting

12

Fretting corrosion

Occurs in metallic devices due to CYCLIC LOADING over time

13

Passivation on metallic surface (increases/reduces) rate of corrosion

Reduces rate of corrosion

14

PLGA degrades to:

Acidic degradation products

15

PLGA/PPHOS composite degrades to:

Neutral byproduct, since PPHOS neutralizes the acidic byproduct of PLGA

16

Calcium Sulfate used for:

Non-load-bearing injectable bone void filler

17

Molybdenum added to stainless steel to:

Increase corrosion resistance AND Hardness

18

Contact angle goniometry measures:

Strength of adhesion and hydrophilicity

Low contact angle = higher adhesiveness

19

Is Scanning Electron Microscopy suitable for live cell analysis?

No, it kills cells -- Specimen must be conductive and in a vacuum

20

Secondary Ion Mass Spectroscopy:

Analysis of surface based on MASS AND FORCE

21

FTIR measures:

Absorbance/transmittance of IR light energy reflected back from a material's surface

22

Tg associated with: ____
Tm associated with: ____

Amorphous polymers = Tg
Crystalline polymers = Tm

23

Sterilization of UHMWPE in ABSENCE of O2 does what?

Increases resistance to wear

24

Change in pH and/or Temp are both methods for:

Desorbing proteins from a surface

25

Bulk degrading polymers, what happens:

Molecular weight is reduced, rate of water penetration exceeds rate of material breakdown - hydrophilic

26

Surface eroding polymers, what happens?

Outside of material peels away like an onion, steady degradation - hydrophobic process

27

Degradation of Poly(lactide-co-glycolide) :

Affects surrounding environment
Undergoes BULK DEGRADATION
Hydrolysis, turns to Lactic acid + Glycolic acid
Degrades a different rates depending on Polylactide:polyglycolide ratio

28

Tissue sterilization of bone allografts (Increases/reduces/eliminates) risk of disease transmission between donor and recipient:

Reduces risk, not eliminate

29

Thermoplasts vs. Elastomers vs. Thermosets, which can be recycled:

Thermoplasts and Elastomers can be recycled
ThermoSET state is SET so they can't be recycled

30

Process of killing organisms causing infection known as:

Sterilization

31

EPOCH hip components

75% less stiff than similar Co-Cr implant (less stress shielding)
Exterior is composed of Titanium Fiber mesh
Core composed of metal - surrounding polymer
Composed of: PAEK, Ti, Co-Cr

32

Nitinol

The nickel-titanium material which goes back to its shape when placed in water

33

Which surface characterization method involves the creation of secondary electrons as part of analysis:

SEM - Scanning electron microscopy

NOT FTIR or Energy dispersive spectroscopy

34

Which methods of analysis provide a "fingerprint"

X-Ray diffraction (bulk analysis)
FTIR (surface analysis)

35

Most common mechanism for degradation in biomedical polymers?

Hydrolytic degradation

36

Advantages of bone autografts:

No recipient immune response
Graft is osteoinductive - with all the growth factors
No disease transfer

37

Osteoinductive vs. Osteoconductive

Osteoinductive = growth factors, osteoblasts stimulated
Osteoconductive = will bone grow on the surface

38

What influences Ca3(PO4)2 deposition

LOW crystallinity HA easily resorbed - more deposition
NaOH and HA can increase deposition

High crystallinity HA is NOT easily resorbed by the body

39

BAK/C implants made from

Titanium Alloy

BAK/C implants are for intervertebral discs

40

Particulate debris from metallic implants results from:

Wear, Fretting, Fragmentation

41

Which metals suitable for hip replacement?

Titanium
Tantalum
Cobalt Chromium
NOT Stainless Steel

42

Hydrogels have what properties

Good stability, refractive index, high oxygen permeability

Degree of cross-linking influences: Degradation, diffusion, mesh size, mech. properties

43

Hydrogels have what functions?

Prevent fluid loss, microorganism entry

Transparency

Injectable for filling in complex shapes

44

Bulk degradation vs. Surface erosion - which for drug delivery

Surface erosion for drug delivery -- Degrades over time = controlled release

Bulk degradation - Mw decreased until material experiences catastrophic failure

45

Benefits of forming polymer/ceramic composite scaffold for bone tissue vs. polymer/ceramics alone

Offset drawbacks of each when used together vs. alone
Polymer offers greater biocompatibility, degradability, and TENSILE strength, and has Greater WORKABILITY.
Ceramic offers greater biocompatibility from ion exchange interactions with bone. It also offers greater COMPRESSIVE strength, but has low ductility. When making degradable materials, a composite can be controlled better than a pure substance.

46

Describe corrosion and passivation -- How does corrosion occur? What is the effect of passivation and how does it perform this effect?

Corrosion = loss of ions = loss of mass over time
2 different metals placed in an environment with conditions that allow for ion exchange
--> Formation of anode/cathode.
The reduction potential difference determines rate of corrosion.

Passivation - formation of thin protective layer on the surface of the metal that protects substance from corrosion by shielding the material from changes in electrical potential

47

Advantage of low crystalline HA over highly crystalline HA:

Natural bone in body is made of low crystallinity HA, which is more easily resorbed by osteoclasts and osteoinductive.
High Crystal HA not as osteoinductive - not easily resorbed.

48

Trabecular metal tech - unique features

Made of tantalum metal - mimics trabecular structure of bone - consists of porous, honeycomb-like structures

Tantalum's porosity allows for much greater biocompatibility with trabecular bone - organic bone can grow on and inside implant, VASCULARIZATION can occur.

49

Design question: New Hip - What materials?

Use Co-Cr alloy, Titanium, PEEK polymer, and Low Crystallinity HA

50

Design new hip - WHY materials

Co-Cr for core - high ultimate stress and fracture stress
PEEK for surrounding the core - for elastic modulus similar to bone - LESS STRESS SHIELDING
Ti alloy mesh for a HA framework on surface - low crystal = more mineral deposition on implant = more osteoinductivity = more biocompatible

51

Design new hip - how to sterilize and why?

Gamma ray radiation, since it penetrates the entire implant and leaves no leftover debris or residue

52

Design new hip - 3 methods of characterization and why

Contact angle goniometer - determine hydrophilicity - know if material will swell in aq. environment

ESCA (Electron spectroscopy for chem. analysis) - determination of groups present on surface - compare to groups present on desired materials (Low Crys. HA and Ti alloy)

FTIR to make unique fingerprint of surface material - in conjunction with ESCA can determine surface materials.

Any impurities can be detected and fixed before further development to mitigate risks of inflammation or recipient rejection of implant.

53

STM vs. AFM

Scanning Tunneling microscopy - Current, and probe with electron cloud detects surface molecules

Atomic Force Microscopy - Probe actually touches surface and detects surface topography

Both very prone to vibrations, and good really only for conductive surfaces.