Introduction:
On January 12th, 1967, James Bedford became the first person to be cryogenically frozen in the hopes of being revived in the future. Cryonics promises to preserve the body until a theoretical future when humanity can cure any illness and reverse death. But to revive people in the future, we need to properly preserve them in the present.
The Science of Cryobiology
Cryopreservation is a technique used to preserve biological matter at very low temperatures (typically below -130°C) to maintain its viability. It involves cooling the sample to a temperature where biological processes are slowed or stopped, and then storing it in a cryoprotectant solution, such as glycerol or dimethyl sulfoxide (DMSO), to prevent damage from ice crystal formation. Cryopreservation is commonly used for preserving cells, tissues, embryos, and gametes, but it requires specialized equipment and careful handling to prevent damage to the sample during the freezing and thawing process.
The Challenges of Cryopreservation
When you freeze a single red blood cell, it typically sits at a temperature of 37 degrees Celsius in a solution of water and chemical solutes, which dissolve under certain conditions. But once the temperature drops below freezing, water outside and inside the cell hardens into damaging ice crystals. Without the correct concentration of water, the chemical solutes are unable to dissolve. And as the water freezes, they become increasingly concentrated in a destructive process known as osmotic shock. Without any intervention, these factors are guaranteed to destroy our red blood cell before it reaches -130 degrees.
Not all cells are this fragile, and many animals have evolved to survive extreme conditions. Some cold-tolerant fish synthesize antifreeze proteins to prevent ice formation at sub-zero temperatures. And freeze-tolerant frogs use protective agents to survive when up to 70% of their body water is trapped as ice. By researching these adaptations, scientists have developed remarkable preservation technologies, some of which are already employed in medicine. However, researchers are still trying to improve cryopreservation technology to better manage the ice problem
Osmotic shock
Osmotic shock is a term used to describe a rapid change in the osmotic environment that cells are exposed to, which can cause damage or death to the cells. Low temperatures can be a cause of osmotic shock in some organisms.
At low temperatures, water molecules in the environment can freeze, leading to a decrease in the water potential outside of the cell. This can cause water to move out of the cell through osmosis, which can result in the cells losing water and becoming dehydrated. This can be particularly problematic for cells that are not adapted to survive in low temperatures, such as those of many warm-blooded animals.
In addition to the direct effects of osmotic shock, low temperatures can also cause other forms of cellular damage, such as the disruption of membranes or the denaturation of proteins. These effects can further exacerbate the damage caused by osmotic shock.
To avoid osmotic shock due to low temperatures, organisms have evolved a variety of strategies, such as the production of cryoprotectants (substances that protect cells from freezing) or the ability to enter a dormant state (such as hibernation or torpor) during periods of extreme cold.
Ice crystals
When biological tissues freeze, ice crystals can form and grow, which can damage cell membranes and other cellular structures. This can lead to irreversible damage and cell death. In cryonics, the goal is to minimize the formation of ice crystals by using cryoprotectant chemicals that reduce the freezing point of water in cells and tissues.
Cryoprotectants work by replacing water molecules in cells with molecules that can tolerate freezing temperatures without forming ice crystals. This reduces the formation of ice crystals and helps to preserve cellular structures. However, the use of cryoprotectants can also be damaging to cells if not used properly, as they can be toxic in high concentrations or if they are not removed before thawing.
Another challenge in cryonics is ensuring that tissues are frozen uniformly so that no part of the tissue is exposed to damaging temperatures or conditions. This requires careful temperature control during the cooling process, as well as specialized equipment and techniques for preserving tissues.
The Vitrification Approach
Many cryobiologists are trying to solve the ice problem with an approach called vitrification. This technique uses chemicals known as cryoprotectant agents (CPA) to prevent ice from forming. Some of these have been adapted from compounds in nature, while others have been designed to take advantage of cryobiology’s guiding principles. These chemicals allow researchers to store living systems in a glassy state with reduced molecular activity and no damaging ice. Vitrification is ideal for cryonics and would help preserve organs and other tissues for medical procedures. But it’s incredibly difficult to achieve. CPAs can be toxic in the high quantities required for large-scale vitrification. And even with these chemicals, preventing ice formation requires rapid cooling that lowers temperatures uniformly throughout the material.
The Challenges of Warming
Even if we could successfully vitrify complex living material, we’d only be halfway to using it. Vitrified tissue also needs to be uniformly warmed to prevent the formation of ice, or worse, cracks. To date, researchers have been able to vitrify and partially recover small structures like blood vessels, heart valves, and corneas. But none of these are anywhere near the size and complexity of a whole human being.
One of the challenges that cryonics faces is the lack of public acceptance and understanding. Many people view cryonics as pseudoscience or science fiction, despite the fact that it is based on sound scientific principles. In addition, the process of cryonics can be expensive and is not currently covered by most insurance plans. This means that only a small percentage of people who are interested in cryonics are able to afford it.
Despite these challenges, there are a number of organizations and individuals who are dedicated to advancing the field of cryonics. Some of these organizations, such as the Cryonics Institute and Alcor Life Extension Foundation, offer cryopreservation services and research opportunities. Other organizations, such as the Society for Cryobiology, focus on advancing the science of cryopreservation and promoting research in the field.
Another area of research in cryonics is the use of nanotechnology to repair damage to cells and tissues. Scientists are exploring the use of nanobots, tiny machines that can be programmed to perform specific tasks, to repair damage to cells and tissues at the molecular level. While this technology is still in its early stages, it has the potential to revolutionize the field of cryonics.
Other preservation technologies
Freezing:
Freezing is a widely used preservation technique for biological matter, including tissue samples, DNA, microorganisms, and cells. It involves cooling the sample to a temperature below its freezing point (typically between -80°C and -196°C) to slow down or stop biological processes that could lead to degradation or loss of viability. Freezing can be used for both short-term and long-term storage, but it requires specialized equipment, such as ultra-low temperature freezers, and careful handling to prevent damage to the sample during the freezing and thawing process.
Formalin fixation:
Formalin fixation is a common preservation technique for tissue samples used in histology and pathology. It involves immersing the sample in a solution of formaldehyde, which reacts with the proteins in the tissue to form cross-links and stabilize the structure of the tissue. The fixed tissue can then be embedded in paraffin wax for sectioning and analysis. Formalin fixation is a relatively simple and inexpensive technique, but it can affect the quality of DNA and RNA extracted from the tissue, and it may not preserve some antigens and enzymes.
Paraffin embedding:
Paraffin embedding is a technique used to preserve tissue samples for histological analysis. It involves embedding the tissue in a block of paraffin wax after fixation, which provides support and allows for the sectioning of the tissue into thin slices for microscopy. Paraffin embedding can preserve tissue architecture and morphology, but it can also affect the quality of DNA and RNA extraction.
Lyophilization:
Lyophilization, also known as freeze-drying, is a preservation technique that involves removing water from a sample by freezing it and then subjecting it to a vacuum to sublimate the frozen water. This results in a dry, stable product that can be stored at room temperature for long periods of time. Lyophilization is commonly used for preserving proteins, peptides, and other biological molecules, as well as microorganisms, but it requires specialized equipment and can be time-consuming.
Ethanol storage:
Ethanol is a commonly used preservative solution for DNA samples, particularly for long-term storage. It denatures proteins and enzymes, preventing degradation of the DNA, and it can be stored at room temperature. However, ethanol can also damage DNA if not stored properly, and it may not be suitable for certain downstream applications.
Types of biological matter to preserve
- Tissue samples: Tissue samples can be preserved using a variety of methods, including freezing, formalin fixation, and paraffin embedding. Freezing is often used for long-term storage, while formalin fixation and paraffin embedding are commonly used for histological analysis.
- DNA: DNA can be preserved using a variety of methods, including freezing, lyophilization (freeze-drying), and storage in ethanol or other preservative solutions. Freeze drying is often used for the long-term storage of DNA samples.
- Microorganisms: Microorganisms can be preserved using techniques such as freezing, lyophilization, and cryopreservation. Cryopreservation involves freezing the microorganisms at very low temperatures (typically below -130°C) to maintain their viability.
- Seeds: Seeds can be preserved using a technique called seed banking, which involves storing seeds in cold, dry conditions. Some seed banks use liquid nitrogen to freeze seeds at ultra-low temperatures for long-term storage.
- Embryos and gametes: Embryos and gametes can be preserved using a technique called cryopreservation. This involves freezing the cells at very low temperatures (typically below -130°C) to maintain their viability.
Conclusion
cryonics is a fascinating field that offers the potential to extend human life and overcome death. While the technology is still in its early stages, there have been significant advances in the field in recent years. With continued research and development, it is possible that cryonics may one day become a viable option for those who wish to extend their lives beyond the limitations of our current biology. However, it is important to remember that cryonics is not a cure for death, but rather a way to potentially extend life until a future time when technology may be able to offer more definitive solutions.
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