Freeze drying, also known as Lyophilization; consists of freezing tissue, then reducing the atmospheric pressure and applying heat to sublimate the water ice in it. A freeze drying machine is a large chamber of heated shelves. Its atmosphere is connected to a vacuum pump and exposed to refrigeration coils.
In the process, the solid is first frozen; creating damaging ice crystals. The vacuum pump lowers the pressure to .6 ATM; ten, the shelves are heated, and due to the low pressure, the ice sublimates directly. This process can take several days (A single (.1386Kg) human brain took 28 to freeze dry. Slicing it, however, reduced the time to 14 days.).
The material, at least in the case of food, can be preserved for several years without decay.
The main advantages of Lyophilization are that the removal of water and oxygen from tissue will reduce decay, and that it does not require expensive equipment or maintenance. A secure container, however, must be obtained and inspected to ensure that Oxygen does not enter the tissues.
The reduced dependence on equipment increases the safety of the storage and reduces the vulnerability of the tissue. There is some overlap in the storage advantages (Namely very low cost and easy storage) of Plastination. Moreover, freeze-dried material can be cryogenically stored later on.
In terms of cost, a single Lyophilization machine, the Taxi-Dry runs at 'less than a dollar a day', and most machines capable of fitting a human brain, head or body cost above $10,000, significantly cheaper than the cheapest perfusion machine.
The most obvious disadvantage is the the Lyophilization process is very destructive it itself. Since freezing happens before dehydration, ice crystals form. When they sublimate, the structural integrity of the tissue is compromised, due to the pores this leaves behind. This might be a solvable problem, but for now, the process is more destructive than the standard Vitrification protocol. Freeze drying also leaves 2% moisture, reducing the storage time to mere years.
Recently, the Brain Preservation Foundation has launched the Brain Preservation Technology Prize, a $100,000+ prize to anyone who can preserve an entire human brain for a long amount of time, such that every neurological feature is preserved and can be examined with today's electron microscopy. Ken Hayworth believes this will be a form of plastination.
Alcohol storage is an old and still widely used preservation method. If storing whole organisms, removal of the intestines is required. Proper storage can be achieved with 70%-90% purity alcohol or methylated spirit. To better preserve the DNA, sodium chloride (Common salt) can be added. 5% Glycerine also supposedly protects the specimen should an accident cause the alcohol to escape or evaporate. The container should be sealed and stored in a dark and cool place, such as a freezer.
The container's alcohol should be replaced at least once, a few weeks after immersion (Or whenever the liquid starts to turn darker or cloudy), as body fluids seep out and contaminate the alcohol. The above-mentioned additives should only be added after the replacement of the alcohol.
While alcohol preservation is very cheap and easy to do, both commercially and DIY (All it takes it some alcohol, a glass container and a freezer), it is overall a very poor preservation method, at least from the perspective of what cryonics tries to achieve: Under a microscopy, they degrade into mush after only a few months.
While biological specimens can be stored for many decades without exterior degradation (Einstein's brain and the Tasmanian Tiger "clone pup", the latter remaining integral after 130 years of alcohol storage), it only preserves macroscopic structure, and maybe enough genetic material to make a clone. Another, less significant issue, is the flammability of alcohol.
|Record Low Temperatures|
|Location||Lowest Recorder Temperature (Cº)|
|Plateau Station, Antarctica||-84ºC|
|Rogers Pass, Montana||-56.5ºC|
- The Permafrost Papers
- Freeze-Drying Biological Specimens: A Laboratory Manual