CTBS Tissue Processing & Preservation 2

Question 1

Which cryoprotectant is most commonly used for bone marrow and hematopoietic stem cell preservation?

Accepted Answer

Dimethyl sulfoxide (DMSO)

Answer

DMSO is the standard cryoprotectant for hematopoietic stem cells due to its ability to rapidly penetrate cell membranes and prevent ice crystal formation.

Question 2

What is the purpose of the 'equilibration period' during cryoprotectant addition?

Accepted Answer

To allow the cryoprotectant to penetrate tissue before freezing

Answer

The equilibration period allows the cryoprotectant to diffuse into cells so it can provide intracellular protection against ice crystal damage during freezing.

Question 3

Which sterilization method is contraindicated for tissues containing viable cells intended for transplant?

Accepted Answer

Gamma irradiation at 25 kGy

Answer

Gamma irradiation at 25 kGy is effective for terminal sterilization but destroys cellular viability, making it unsuitable for cell-based allografts.

Question 4

During freeze-drying (lyophilization), what is the PRIMARY mechanism of tissue preservation?

Accepted Answer

Removal of free water to halt metabolic and microbial activity

Answer

Lyophilization preserves tissue by sublimating water under vacuum, leaving a dry matrix that resists microbial growth and enzymatic degradation.

Question 5

What is the recommended storage temperature for lyophilized (freeze-dried) bone allografts?

Accepted Answer

Room temperature (15–30°C)

Answer

Freeze-dried allografts have sufficiently low water activity that they can be stored at room temperature in sealed, moisture-proof packaging.

(CTBS) Certified Tissue Bank Specialist Practice Test

(CTBS) Certified Tissue Bank Specialist Practice Test

CTBS Tissue Processing & Preservation 2