The science of life at low temperatures, literally referring to cryobiology, has a number of applicable areas when considering carbon dioxide (CO2) as a merchant gas.

Often, this product would be sought as a USP (United States Pharmacopeia), which is a very small percentage of the merchant fleet of plants available – however, this grade would be strictly used as a respiratory stimulant, and often for many applications considered to have a medical basis behind the use.

The refrigeration value available and utilised in a range of applications, when referring to cryobiology, would range from a moderate cooling effect - moderately hypothermic – to cryogenic temperatures.

The application of carbon dioxide can affect biological materials ranging from proteins, cells, tissues, organs, and ultimately organisms. More specifically, and categorically speaking, this application can include the following:

Cryosurgery – usually minimally invasive approach of unhealthy tissues using CO2.

Cryopreservation of biological materials from cells, tissues, gametes, to embryos of animal and human origin. This preservation can be of a long term nature and if long term, usually for success to be achieved, specific substances need to be added to the samples – thus protecting the cells during freezing and thawing.

Hypothermic conditions, or temperatures that are less than metabolic readings, thus suitable for transplant of tissues. Along these lines, CO2 as a coolant can be used (dry ice or liquid CO2) in the transport of these (often) life saving tissues, to the surgical theatre.

Certain specific applications for lyophilisation(freeze-drying processes) in production of pharmaceuticals.

Although much of the application in the field of biologicals, and more specifically cryosurgery and cryobiology, often think in terms of physically removing keratosis and skin cancers via freezing, with liquid CO2 (LCO2), liquid nitrogen (LIN) and other agents, there are a wide variety of applications beyond this ‘old school’ technique.

In fact, many more CO2 – based cryobiological applications are available. Further still, cryobiological applications are a world apart from a critical application of USP grade CO2 in respiratory stimulation alone. Respiratory stimulation specifically can bring back the patient from the brink, quite literally. As this small volume market alone, respiratory stimulation would require USP grade (a very small total market within the greater merchant CO2 production plant holdings) CO2 up to about 5% by air volume (rather than atmospheric CO2 at .039%).

In addition to the very small respiratory market as mentioned above is the predominant greater market defined as cryobiological – that being application of carbon dioxide as a liquid or solid in temperature reduction and low temperate settings and (cold) storage of various forms of tissue.

Cryosurgery
Cryosurgery in a fairly common setting includes cryogenic in-situ of carcinoma, such as the removal of abnormal cells which often remain in place for a period of time, thus preventing an otherwise spread to outside healthy tissue, such as the so-called common keratosis or skin cancers.

The application is via LCO2 from a nozzle to the tissue in question. The same is also achievable via dry ice; however, the use of liquid or ice is a function of availability, and convenience. When speaking of these procedures, specifically removing abnormal tissue, this is not the cure for skin cancer or melanoma; however it is the removal of non-malignant tissue, moles, and viral-based warts.

Cryobiology
Cryobiology at large, generally deals with the chemical and biological aspects of cryopreservation of biological materials.

This greater field, from a viable and ethical perspective, in my thinking would generally exclude concepts such as long-term storage of whole or partial human or animal bodies (such as a head); with the long-term intentions to ‘reanimate’.

Deep freezing via cryogenics will generally render some tissue damage and with technologies today (and for the foreseeable future), the damage to tissue via cryonics, and other factors relating to general feasibility and ethics makes the case for cryonics less than a viable concept. This does not exclude the cryogenic storage of tissue as preservation for sampling of DNA and other, similar concepts.

Reanimating long-lost family members cryogenically frozen, is the stuff of science fiction and probably impossible, thus the cryonic storage facilities that hold parts of or whole bodies for reanimation is probably a hoax – or at best, an impossible hope.

Skin rejuvenation & aesthetics
With respect to a growing and successful skin rejuvenation practice via CO2 lasers, dermatologists can turn to carbon dioxide erbium laser resurfacing – which has demonstrated strong success in the removal of sun-damaged skin, eye wrinkles, smoker’s lip lines, and other cosmetic challenges.

Of course, in addition to the removal and rejuvenation of skin lesions and age-related damage, would be the use as a coolant in the many applications whereby CO2 is used in organ and tissue storage, and the additional refrigeration value in cryotransport (dry ice) of vital organs, blood, and various tissues and tissue samples to refrigeration, for reuse and application of said tissues.

The refrigeration value from LCO2 and dry ice would enhance alcohol bath-cooling capabilities. Cryogenic freezers using LCO2 are also applicable to the science of cryobiology. In this context, replacing mechanical systems that may not even be applicable, can be well achieved by the portability of dry ice, or the use of LCO2 – thus saving electricity, in theory a green application.

Concluding thoughts
In summary, CO2 usage in the laser-repair of damaged skin, chilling tissue samples and blood for transport, surgical re-attachment, storage, and similar biological applications (as well as the use in chilling & freezing mechanisms, from alcohol baths to cryogenic freezers) – all of these are prime examples of cryobiology and CO2 working together.

The advantages of the science of cryogenics are well demonstrated when considering specific applications in the medical field, essential and consistent when working with life-sustaining biologicals and tissues for human and animal life.

The application of CO2 will continue to grow in this field, and the specific demands today and tomorrow are quite fascinating, in my opinion.

Considerations for cryogenics
With respect to freezing and thawing via CO2 application, the basic nature of cryogenic freezing should be considered, whereby cryogenic freezing would limit the sharp ice crystals usually formed through the slower and warmer temperatures used in alternate means of freezing, such as mechanical methods.

This therefore limits tissue damage, essentially as fewer sharp ice crystals are formed during freezing, which then result in penetration of the cellular walls, and further result in leakage of cellular fluids. Thus cryogenic is the strong advantage in this scenario.