Presentation Exam Qs Midterm 1

Question 1

Why Alginate beads instead of alginate bolus

Answer 1

All the cells in the middle of a large block would be killed - To minimize diffusion limitations… More surface area to volume ratio

Question 2

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

Answer 2

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

Question 3

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

Answer 3

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

Question 4

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

Answer 4

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

Question 5

The effect of the micropattern on cell growth:

Answer 5

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

Question 6

What substrate parameters can be modified to control cell differentiation?

Answer 6

Stiffness, topology, size, surface area, available functional groups

Question 7

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

Answer 7

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

Question 8

How did macromer lengths affect sol-gel temperatures?

Answer 8

Longer lengths decreased sol-gel temperature

Question 9

How did changing modulus affect cellular growth and differentiation

Answer 9

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

Question 10

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

Answer 10

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

Question 11

What is the rationale behind bimodal distribution of pore sizes?

Answer 11

Small pore sizes favor oxygen and nutrient transport

Large size support vasculature and tissue growth

Question 12

Benefits of bioglass composite scaffold?

Answer 12

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

Question 13

Why controlled release of growth factors?

Answer 13

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

Question 14

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

Answer 14

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

Question 15

Difference between storage and loss modulus of a hydrogel?

Answer 15

Storage modulus measures elastic deformation of hydrogel

Loss modulus measures viscous portion of hydrogel

Question 16

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

Answer 16

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

Question 17

What is secondary crosslinking within hydrogels?

Answer 17

When they crosslink after the printing to increase mechanical properties

Question 18

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

Answer 18

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

Question 19

What is the relationship between porosity and elastic modulus?

Answer 19

More pores = lower modulus. Less pores = higher modulus