CTBS Tissue Processing & Preservation 4 — Questions and Answers
Question 1: What is the primary purpose of adding albumin to cryopreservation media for vascular tissue?
- To lower the freezing point of the solution
- To act as a membrane stabilizer and colloidal oncotic agent (Correct answer)
- To serve as the primary cryoprotectant
- To inhibit viral replication during storage
Correct answer: To act as a membrane stabilizer and colloidal oncotic agent
Albumin stabilizes cell membranes during osmotic stress and maintains colloid osmotic pressure to reduce cell swelling during the freeze-thaw process.
Question 2: When gamma irradiation is used for allograft sterilization, what is the MOST significant concern regarding biomechanical properties of tendon allografts?
- Increased water content
- Dose-dependent reduction in tensile strength (Correct answer)
- Enhanced collagen cross-linking improving strength
- Increased antigenicity
Correct answer: Dose-dependent reduction in tensile strength
High-dose gamma irradiation degrades collagen fibers through free radical generation, leading to measurable dose-dependent reductions in tensile strength.
Question 3: A technician notices ice crystal formation on the outside of cryopreservation bags during controlled-rate freezing. This MOST likely indicates:
- The freezing rate is too slow
- Nucleation has occurred and latent heat release may cause a temperature spike (Correct answer)
- The cryoprotectant concentration is too high
- The tissue is already fully frozen
Correct answer: Nucleation has occurred and latent heat release may cause a temperature spike
External ice crystal formation signals nucleation, which releases latent heat and can cause a temporary temperature rise (recalescence) that must be managed by the controlled-rate freezer.
Question 4: Which property of glycerol makes it suitable as a cryoprotectant for red blood cells but less ideal for most other tissue types?
- It permeates cells very slowly, limiting utility to small-volume tissues
- It requires high concentrations (40%) and lengthy deglycerolization before use (Correct answer)
- It causes significant lipid peroxidation during storage
- It is only effective above -40°C
Correct answer: It requires high concentrations (40%) and lengthy deglycerolization before use
Glycerol works well for RBCs but requires high concentrations and extensive post-thaw washing (deglycerolization) to remove toxic levels before transfusion, limiting practicality for complex tissues.
Question 5: What does the term 'terminal sterilization' mean in the context of tissue banking?
- Sterilization performed at the end of the donor's life
- A sterilization process applied to the final packaged product (Correct answer)
- Sterilization of processing equipment after each use
- The final antibiotic soak step before freezing
Correct answer: A sterilization process applied to the final packaged product
Terminal sterilization refers to a validated sterilization method (e.g., gamma irradiation, EO gas) applied to tissue in its final container after all processing is complete.
Question 6: Which factor is MOST likely to reduce the efficacy of ethylene oxide (EO) sterilization of a tissue allograft?
- Low processing temperature
- Excessive moisture trapped within the tissue (Correct answer)
- High EO gas concentration
- Prolonged aeration time
Correct answer: Excessive moisture trapped within the tissue
Excess moisture can react with EO to form ethylene glycol residues and may also impede gas penetration, reducing sterilization efficacy and leaving harmful byproducts.
Question 7: During aseptic processing of tissue, which environmental monitoring parameter is used to assess viable airborne contamination?
- Particle count (non-viable)
- Active air sampling using impaction samplers (Correct answer)
- Temperature and humidity logging
- HEPA filter pressure differential
Correct answer: Active air sampling using impaction samplers
Active air sampling with devices like impaction or centrifugal samplers collects viable microorganisms from the air to assess biological contamination risk in clean rooms.
CTBS Tissue Processing & Preservation 4
What is the primary purpose of adding albumin to cryopreservation media for vascular tissue?