CTBS Processing Techniques 2 — Questions and Answers
Question 1: Which solution is most commonly used for terminal sterilization of bone allografts via chemical means?
- Peracetic acid (PAA) (Correct answer)
- Sodium hypochlorite
- Glutaraldehyde
- Hydrogen peroxide gas plasma
Correct answer: Peracetic acid (PAA)
Peracetic acid is widely used for terminal sterilization of bone allografts because it is sporicidal, leaves minimal toxic residues, and is compatible with bone matrix.
Question 2: What is the primary purpose of demineralization in bone allograft processing?
- To increase the mechanical strength of the graft
- To expose bone morphogenetic proteins and enhance osteoinductivity (Correct answer)
- To reduce immunogenicity by removing cellular antigens
- To extend the shelf life of the graft
Correct answer: To expose bone morphogenetic proteins and enhance osteoinductivity
Demineralization removes calcium phosphate mineral to expose bone morphogenetic proteins (BMPs) embedded in the collagen matrix, significantly enhancing the osteoinductive potential of the graft.
Question 3: During skin allograft processing, which step is performed to reduce bioburden prior to cryopreservation?
- Lyophilization at -40°C
- Antibiotic solution soaking (Correct answer)
- Gamma irradiation at 25 kGy
- Electron beam sterilization
Correct answer: Antibiotic solution soaking
Skin allografts are typically soaked in antibiotic solution cocktails (e.g., gentamicin, vancomycin) to reduce bacterial bioburden before cryopreservation.
Question 4: What does the term 'bioburden' refer to in the context of tissue processing?
- The weight of the tissue after dehydration
- The number of viable microorganisms present on or in a tissue before sterilization (Correct answer)
- The amount of residual chemical sterilant remaining in tissue
- The immune cell count in unprocessed tissue
Correct answer: The number of viable microorganisms present on or in a tissue before sterilization
Bioburden refers to the total number of viable microorganisms present on or in a tissue before sterilization, and monitoring it is critical to validating sterilization processes.
Question 5: Which processing technique is specifically designed to preserve the viability of chondrocytes in cartilage allografts?
- Lyophilization with sucrose cryoprotectant
- Controlled-rate cryopreservation with DMSO (Correct answer)
- Chemical dehydration with acetone
- Gamma irradiation at 15 kGy
Correct answer: Controlled-rate cryopreservation with DMSO
Controlled-rate cryopreservation using DMSO (dimethyl sulfoxide) as a cryoprotectant is used to maintain chondrocyte viability in osteochondral and cartilage allografts.
Question 6: What is the Sterility Assurance Level (SAL) required for implantable tissue allografts according to AATB standards?
- 10⁻³
- 10⁻⁶ (Correct answer)
- 10⁻⁴
- 10⁻⁸
Correct answer: 10⁻⁶
AATB standards require a Sterility Assurance Level (SAL) of 10⁻⁶, meaning a probability of no greater than one in one million chance of a viable microorganism being present.
Question 7: In the context of tissue processing, what is 'decellularization' intended to achieve?
- Removal of cellular and nuclear material to reduce immunogenicity while preserving extracellular matrix (Correct answer)
- Destruction of all microbial contaminants including prions
- Extraction of growth factors for separate therapeutic use
- Removal of lipids to improve mechanical properties
Correct answer: Removal of cellular and nuclear material to reduce immunogenicity while preserving extracellular matrix
Decellularization removes cellular and nuclear material (including antigens) from tissue while preserving the extracellular matrix scaffold, reducing immunogenic response upon transplantation.
CTBS Processing Techniques 2
Which solution is most commonly used for terminal sterilization of bone allografts via chemical means?