Storing biological components almost indefinitely, without any change or degradation in cells. That is the goal of sample storage or cryopreservation.
But what exactly is sample storage? What types of refrigeration systems exist, and how does Demaco help the medical industry and the pharmaceutical industry with a safe liquid nitrogen supply? Read on for detailed answers to these questions. Read on for detailed answers to these questions.
What is sample storage?
Sample storage is the refrigerated storage of small amounts of biological material for purposes like medical procedures, experiments, or pharmaceutical production. This material can be anything. They may include blood, cells, semen, certain vaccinations, or other materials that must be kept in perfect condition for a long time.
While food is often stored in a “common” freezer of about – 18°C, sample storage requires other refrigeration methods. Due to the relatively high temperature and unregulated cooling in standard freezers, ice can form, heat leaks in, and crystals form in the material. These crystals damage the cells, and once thawed, they no longer have their original shape and quality.
This is where special refrigeration systems for sample storage offer the solution. Thanks to the lightning-fast cooling to extremely low temperatures and the stability provided by these systems, the material is not damaged and can be stored in perfect condition for a long time.
Different types of refrigeration systems
The goal of sample storage is almost always the same: to slow or stop the degradation of biological material. How this is achieved varies considerably. There are several types of refrigeration systems, all of which bring the material to a low temperature in their own way.
While cryogenic techniques are usually thought of when considering sample storage, there are other possibilities. For example, there are several types of mechanical freezers that, like cryogenic cooling systems, can quickly reach relatively low temperatures.
Often mechanical refrigeration systems for samples achieve a temperature of about -40 to – 80°C using a refrigerant such as ethane or propane.
Mechanical refrigeration systems have the advantage that the racks with samples are easily accessible due to the high and straight shape of the system. However, the range in temperature with these freezers is limited, and there is a risk of damaging samples in case of technical problems or a power failure.
Refrigeration with gaseous nitrogen
A second type of refrigeration system for sample storage uses gaseous nitrogen as the refrigerant.
Cooling in nitrogen gas usually occurs in a round vessel with a liquid nitrogen supply at the bottom. A layer of gaseous nitrogen forms above this, in which the samples are kept.
The advantage of this method is the low temperatures that can be achieved and the flexibility in temperature. The temperature of these freezers that the user can set is usually between -135°C and -190°C.
A cooling system with nitrogen may also cause technical problems. Still, the likelihood of this is less than with a mechanical freezer. The system contains fewer mechanical parts and requires less energy, which allows the use of a backup battery to avoid problems in the event of a power failure.
Round barrels of nitrogen often contain a rotatable rack in which the samples can be reached from the top.
Cooling with liquid nitrogen
Gaseous nitrogen offers many possibilities, but liquid nitrogen is needed for the very lowest temperatures. Therefore, we also see this type of cooling system frequently in the medical and pharmaceutical industry.
Cooling systems for sample storage in liquid nitrogen are often round and very similar to those for gaseous nitrogen. The only difference is that the samples are placed directly in the liquid rather than in the gas.
The significant advantage of cooling in liquid nitrogen is the ultimate low and stable temperature of -196°C, which ensures the very best protection of the cooled materials. Cell activity is completely halted at this temperature, and the sample should theoretically have an infinite shelf life.
However, working with liquid nitrogen has one disadvantage: some safety risks come into play when opening the container, and some liquid evaporates. Therefore, this method is ideal for samples to be stored unstirred for an extended period or while they are transported.
In case regular access to the samples is required, cooling in a mechanical system or gaseous nitrogen is usually the preferred method.
Automated sample storage
Last but not least, perhaps the ultimate solution for secure large-scale sample storage: is automated sample storage.
Cooling systems for automatic sample storage are relatively large. They contain a space cooled with gaseous nitrogen in which the samples can be stored as well as manipulated.
The advantages of this method include the following:
- The system contains advanced built-in software that automatically records the samples. This allows real-time tracking and significantly reduces the chance of samples being lost or swapped.
- The samples are placed in the system by a robot and removed or processed when necessary. This keeps the system closed and the temperature very stable.
- Tests show that samples heat up about four times faster and are exposed to temperatures above Tg for about two times longer in a manual process than in an automated process. The automatic handling of samples saves labor costs and is very safe. Employees do not come into direct contact with cryogenic liquids, which reduces the risk of accidents.
Variants and additional applications
Of course, the above systems are not the only applications and solutions that contribute to successful sample storage.
The following applications and products can also be found in the biobanks of various pharmaceutical laboratories or medical institutions:
- Refrigeration systems that cool with gaseous nitrogen as well as liquid nitrogen.
- Some biological materials damage when placed directly in liquid nitrogen. Cooling them first in nitrogen gas and then placing them in liquid nitrogen solves this problem.
- So-called controlled-rate freezers (mechanical or cryogenic) that bring the temperature down in a controlled manner in one system, in a way that preserves a specific material as best as possible.
- Special dewars in various sizes for transporting samples.
- Filling stations specifically designed for filling the above dewars or portable cooling systems for sample storage.
- Software and displays for managing and recording samples.
- All necessary tubes and racks for sample storage.
- Quality improvement products for liquid nitrogen of the best quality.
- Cryogenic infrastructures to route nitrogen from a storage tank to a refrigeration system or dewar for sample storage.
Demaco and sample storage
Whatever design a cryogenic refrigeration system may have, it requires a supply of liquid nitrogen. The proper cryogenic infrastructures are essential to set this up efficiently and safely.
Demaco helps institutions in the pharmaceutical and medical industry with the cryogenic applications and transfer lines that control the supply of liquid nitrogen.