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Tissue Engineering > Running Deck > Flashcards

Running Deck Flashcards

1
Q

Why Alginate beads instead of alginate bolus

A

All the cells in the middle of a large block would be killed - To minimize diffusion limitations… More surface area to volume ratio
- ALSO Encapsulation in general prevents unwanted cell migration

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2
Q

How can you edit the amount of cross-linking of alginate?

A

Charge the molarity of the cross-linking reagent (Calcium chloride)

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3
Q

What is the ideal location in an animal model for a biocompatibility study

A

Subcutaneous - Easy to get to, minimally invasive
Don’t have to account for immune response of the surgery itself
Eliminate variables that you would get at a more invasive site
Isolate the immune response to be caused by the injection and not by the surgery itself

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4
Q

What situation would you want to use a t-test vs. ANOVA

A

T-test for 2 things, ANOVA for more since p-values can compound and make multiple t-tests inaccurate for a set of many things

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5
Q

The effect of the micropattern on cell growth:

A

With the pattern, there is less space for the cells to grow and proliferate

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6
Q

What substrate parameters can be modified to control cell differentiation?

A

Stiffness - Depending on stiffness, different amounts of growth factors were observed
Size - Lots of room (SURFACE AREA), more proliferation
Available functional groups - Cells interact differently with different functional groups

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7
Q

What was the purpose of using a hydrogel in tissue engineering for this study?

A

Similar rate of degradation and other properties with the surrounding tissues and cell types, in terms of mechanical and chemical properties

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8
Q

How did macromer lengths affect sol-gel temperatures?

A

Longer lengths decreased sol-gel temperature

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9
Q

How did changing modulus affect cellular growth and differentiation

A

Closer you get to the modulus of the tissue, the most significant differentiation occurs
Most significant MYOGENIC DIFFERENTIATION occurred at 20 kPa, modulus of tissue is 17 kPa

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10
Q

Describe a method to use poragen leaching that ensures a continuous interconnected pore structure and reduces the likelihood of leaving behind residual poragen

A

Sintering the Poragen so that it forms interconnected pores and dissolves all the way

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11
Q

What is the rationale behind bimodal distribution of pore sizes?

A

Small pore sizes favor oxygen and nutrient transport

Large size support vasculature and tissue growth

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12
Q

Benefits of bioglass composite scaffold?

A 
High compression modulus
High Tg
Fastest degradation rate
Low inflammation
Effectively repaired bone defect
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13
Q

Why controlled release of growth factors?

A

Can target proliferation and differentiation of cells at different stages of development or cell growth

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14
Q

What electrospinning parameters can you change to control release kinetics from nanofibers?

A

Voltage difference, viscosity of solution, rate of motion of the target, injection rate with which the solution is injected, all to modulate the nanofiber diameter - which effectively changes the exposed surface area of the nanofibers

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15
Q

Difference between storage and loss modulus of a hydrogel?

A

Storage modulus measures elastic deformation of hydrogel

Loss modulus measures viscous portion of hydrogel

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16
Q

On a time sweep from rheological data, (Time on x axis, stress on y axis) when does gelation occur?

A

Gelation occurs at the crossover point between the storage modulus and loss modulus

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17
Q

What is secondary crosslinking within hydrogels?

A

When they crosslink after the printing to increase mechanical properties

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18
Q

What’s the importance of having a Ca/P ratio below 1.67? What type of Ca/P does it indicate?

A

Make it more easily resorbable, it is called “Calcium deficient Hydroxyapatite”

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19
Q

What is the relationship between porosity and elastic modulus?

A

More pores = lower modulus. Less pores = higher modulus

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20
Q

Does anatomical location of mesenchymal stem cell isolation matter?

A

Yes, they differentiate differently based on where in the body they are from

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21
Q

Primary vs. Cell Lines

A

Primary = Expensive, but accurately simulate in vivo
– Primary are heterogeneous, first plating, may have other cells in addition to desired cell - Used for Gene therapy
Cell lines, cheaper - may mutate and are used for in vitro
testing conditions where many conditions are tested, more proof of concept

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22
Q

When to use embryonic or induced progenitor stem cell?

A

Since they self-renew, use for a patient w/ autoimmune neurodegenerative disease as the embryonic stem cells can regenerate

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23
Q

Mesenchymal stem cells in what use?

A

Artificial hip in order to promote osteoinductivity along the pores of the replacement hip

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24
Q

For testing the stemness of cells, what is added to each type?

A

Fat - Oil Red O staining to TEST for adipogenesis
Type II collagen used for testing for cartilage
Alkaline Phosphatase for testing for osteogenesis

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25
Q

How to separate cell types, 2 ways

A

by density- centrifugation

by fluorescent tags and electrostatic charging - then run through electric field to separate different cell types

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26
Q

How to modify a solid material to change properties?

A

Drill holes in it!

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27
Q

Different combinations of Polylactide and Polyglycolide

A

Get properties between the two, you can control the ratio

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28
Q

How to make bone cement porous

A

Mix degradable polymer into bone cement like poragens to make it porous

29
Q

Harm of too much or too little decellularization

A

Too much = ECM harmed

Too little = Inflammatory response from remaining cells

30
Q

How to remove cells (decellularize)

A

Physically = shake them, freeze thaw
Enzymatic = Trypsin, endonucleases
Chemical - Alkaline, acid

31
Q

Influence of fluid flow and dynamic loading on cell

A

Cell experience of pull shear or stretch can influence how it grows and proliferates

32
Q

Forces and cells

A

Cells have forces applied onto them, but they also APPLY FORCES to their partners
ex. Change the stiffness of areas of a scaffold to create varied effects when adding cells to the scaffold

33
Q

How can bone growth be stimulated?

A

Ultrasound or EM waves

34
Q

Pros/Cons of injectable cell based therapies

A 
Pros = minimal invasive, reduce risk + healing time,
Cons = low cell survival and retention rate
35
Q

Types of stem cells

A 
totipotent can be any tissue
pluripotent = any of 3 germ layers
Multipotent = multiple tissue types
mesenchymal can be bone, fat, or muscle 
iPS = Can be reversed and then redifferentiated
36
Q

How to induce differentiation

A

Addition of growth factors, chemical stimuli
Co-culture with another cell type
Physical manipulation - Culture beyond confluence or modulate fluid flow over cells

37
Q

Polyethylene importance

A

Mech properties in the range of bone, depending on molecular weight

38
Q

Hydrogel importance

A

Drug delivery, drug eluted when matrix swells

Natural material - good biocompatibility

39
Q

Ceramics importance

A

Bioactive glass (providing Ca or P ions into solution), good osteoinductivity - results in strong cohesive strength between implant and bone

40
Q

Requirements for scaffold design

A

Tissue independent: Biocompatible, tunable properties (mechanical, structural, topographical, degradable)

Tissue Dependent: Mechanical, degradation time, pore structure, overall shape and structure, surface functionality

41
Q

Photolithography

A

Coated surface resists imprinting by beam - results in textured surface - Cells can grow

42
Q

Relevance of microfluidics

A

Capillary analysis and design - mimicking smallest level of fluid flow to understand shear forces on relevant cells

43
Q

Nanofibers use

A

to replicate ECM to give cells a familiar environment

44
Q

Random vs. aligned nanofibers

A

Aligned for tendons and ligaments

Random for collagen

45
Q

Sterilizing decellularized ECM

A

Can change mech props based on dose and method

and change bioactivity - ethylene oxide induces immune response

46
Q

What is move favorable, a slow sustained release of BMP-2 or a rapid diffusion over a period of a few hours? Why?

A

Days because the lower concentration prevents negative side effects

47
Q

Is it bad for molecules to display brownian motion during delivery? How can we avoid this?

A

Brownian will carry anywhere, may not target tissue

Localized drug delivery would help

48
Q

Could bottom up delivery of BMP-2 be used in other types of biomaterials/structures? Do you think this method would be more advantageous?

A

Stiffness of surface affects cell behavior

Could be either, different reasons why

49
Q

Why is a protective sheath or shell beneficial for a protein delivery system such as the one described here?

A

Increases time of viability

Molecule can diffuse farther

50
Q

What follow-up studies would be recommended to further develop this system towards the clinical applications we previously discussed?

A

In vitro, multiple cell types
In vivo
Attempting to carry/release other types of molecules

51
Q

Figure 5 - release kinetics. Could the fact that there is a dramatic pH change be used to their advantage?

A

Yes, pH in saliva very different than pH in stomach where it is very acidic
Could engineer it to pass through stomach and release in GI tract

52
Q

Issues with high dosages of BMP-2 and what are 2 ways they can be circumvented

A

Issues: Adiopogenesis, inflammation, cyst like bone formation, ectopic bone formation
Solutions: Upregulation of Phenamil, use less BMP 2 bc there are only picograms in the body

53
Q

What is the function of a knockdown?

A

To create a negative control in the design

54
Q

Why is PRP beneficial for creating vascular networks?

A

PRP gel contains the growth factors needed so additional ones are not required

55
Q

What needs to be considered when developing PRP gels for in vivo study?

A

Degradation, cell viability, stiffness (stimulate bone = make cells stiffer), site implantation

56
Q

Piezoelectricity

A

Ability of certain materials to generate electric charge in response to mechanical stress or vice versa - based on crystal lattice

57
Q

Static vs. Pulsed EM Field

A 
Static = rare earth magnet, static field, strong health applications
Pulsed = dynamic, pulsed
58
Q

Clinical bone repair

A 
Surgical = bone grafts
Non-invasive = Ultrasound, EM stimulation
59
Q

Electrostimulation

A

Low level electric current to tissue –> alteration in intracellular calcium –> Increased activated calmodulin –> increase proliferation of bone

60
Q

LIPUS

A

Low Intensity Pulsed Ultrasound - stimulates bone and causes it to reform and repair,
It can be modulated to deform hydrogels more or less depending on force provided by LIPUS

61
Q

Capacitive coupling

A

Electrodes placed on either side of fracture, creates alternating current

62
Q

Inductive coupling

A

EM Field around fracture, low frequency (LIPUS) or combined (CEMF)

63
Q

PMA

A

Pre market approval - safe AND effective, 1% of new devices

64
Q

510k

A

premarket clearance - establish that a device is substantially equivalent to a previously cleared device, (previous device = “Predicate”)

65
Q

Class 1, 2, 3 devices

A

1: little to no risk (bandages)
2: higher risk, (needles, monitors, implanted devices)
3: Clinical trials, high risk

66
Q

Hydrogels have ____ bonds with ___ interactions

A

covalent, many interactions

67
Q

Poragen leaching results in products that are always interconnected T/F

A

False, not always interconnected

68
Q

Polylactide true facts

A

Tunable mech properties depending on final form of scaffold
Relatively hydrophobic compared to polyglycolide
Degrades over longer period of time than polyglycolide (6 months to 2 years)

Tissue Engineering (2 decks)

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