Approaches to Biopreservation Flashcards
Importance of Biopreservation
- ability to separate donor and recipient in space and time
- preservation of cell viability and function outside of body
= allows quality control, compatibility matching, transport, transfusions, transplants
List 4 biopreservation methods
1. Hypothermic storage
2. Cryopreservation
3. Vitrification
4. Lyophilization
Hypothermic Storage
- storage temp > physiological temp (0 to 37 °C)
- finite shelf-life to limit cell damage
- used for cells (blood, stem, PLT), tissues, and organs
Cryopreservation
- temp less than -80°C
- long-term preservation of function
Principle of Cryobiology
freezing = liquid turns to solid ice = solutes in remaining water become concentrated (increased osmolality) = freezing point drops to eutectic point (everything is solidified)
NOTE: eutectic point differs for every solute
Cooling rate in Cryopreservation
slower cooling rates = higher cell survival
- rapid cooling causes crystal formation that damage cells
Cryoprotectants
- additives to minimize damage from cryopreservation
- permeating (cross membranes) ORnon-permeating
Increased cryoprotectant results in __ amounts of __ by __
Increased cryoprotectant results in DECREASED amounts of ICE FORMATION by LOWERING FREEZING TEMP OF ICE
Non-permeating Cryoprotectants
- dehydrates cell by increasing extracellular osmolality
= decreases intracellular ice formation - rapid cool without damaging cells
Disadvantages of Non-permeating Cryoprotectants (CPA)
- high concentrations = toxic
- must carefully add/ remove CPA to prevent cell damage from osmotic changes
- cell-specific; eutectic point differs for every solute
- cannot preserve all tissues or any organs (multiple cell-types)
Vitrification
- solidification of liquid using high [CPA] and high cooling rates
- progressive increase in viscosity preventing cell damage due to ice formation
Disadvantages of Vitrification
- high concentrations of [CPA] = toxic
Lyophilization
“Freeze-drying” under a vacuum:
1. ice sublimated directly to vapor
2. moisture removed from sample
- stored in RT
- long-shelf life
Disadvantages of Lyophilization
- cell damage due to drying
