Laboratory freezers are the refrigerated cabinets employed for storing biological samples and reagents in animal laboratories at temperatures ranging from -80oC to 10oC. Portable freezers are used to transfer biodegradable specimens; explosion-proof freezers are required to store flammable vapors, which might explode at room temperature; ultra-low temperature freezers are used to store products below -40oC for a long time. In addition to these, freezer-fridge combinations are used in laboratories that possess two or more cabinets serving as both fridges and freezers. Different types of freezers and combos serve different purposes. For instance, -30oC freezers store plasma, while those operating at -20oC store enzymes. Laboratory freezers and combos are used in pharmaceutical facilities, research labs, and material testing.
Why should you freeze biological specimens?
Freezing biological specimens at low temperatures is the current “gold standard” for storing biological samples. The purpose of freezing biological samples is to store them for long-term usage without damaging their structural and metabolic integrity. The process of preserving biological cells and tissues at very low temperatures while keeping them structurally intact is called “cryopreservation.” Cryopreservation protects individual cells and biological tissues in a living state with suspended cellular metabolism at a very low temperature. This technique is pivotal in biochemistry and biotechnology research, clinical medicine, zoology, and botany.
The researchers can store cell and tissue cultures, oocytes, embryos, stem cells, hepatocytes, etc., for research and clinical purposes. They freeze the desired cells or biological specimens for future studies. Cell storage in labs is an “insurance policy” in cell shortage, contamination, or experiment failure. The metabolic activity and cellular growth are ceased during freezing: however, when the cells are thawed, they retain their original characteristics. The researchers can also use freezers to store biological specimens, protecting them from contamination.
Types of Freezers
Chest freezers have a top opening instead of a front door. These are conventionally large pieces of storage equipment that offer ample storage space for animal research facilities. They possess alarm systems to indicate temperature changes, locks, and digital temperature displays. However, the absence of shelving is a factor that makes them unsuitable for laboratories that require high-level storage and organization.
Ultra-low Temperature Freezers
Ultra-low temperature (ULT) freezers preserve frozen specimens and vaccines for biological labs and pharmacies. They maintain temperatures between -40oC and -86oC. ULT freezers maintain this temperature by two independent evaporator circuits surrounding the interior temperature.
The devices possess a temperature monitoring system, twin compressors to maintain extremely low temperatures, and wax-free synthetic oils to prevent ice buildup. The ambient temperature must be low in laboratories equipped with ULT freezers. They should be adequately spaced to allow proper ventilation, kept in rooms with temperatures no less than 32oC, and not exposed to direct sunlight.
Under-counter freezers are the best storage solution for labs with less space. They can be easily adjusted under benches and counters, thus saving enough space for other lab equipment and activities. Various under-counter freezer designs include explosion-proof, flammable material storage options, different sizes, adjustable temperature ranges, and defrost frequency controller to prevent unwanted thaws and sample dehydration.
Upright freezers are common in research laboratories and medical institutions. The purpose of upright freezers is to maximize temperature consistency by exposing all lab samples to the same conditions. They ensure recovery time reduction after door opening.
Upright freezers have a front opening door, and therefore, they resemble domestic refrigerators used for storing groceries. These freezers usually have shelving in their interior. Upright freezers provide ample storage space for samples yet occupy less lab space due to their vertical design. They are popular in the medical sector because of their spatial efficiency.
Fridge-freezer combinations are ideal for labs with a small footprint. As the name suggests, the device contains both refrigeration and a freezing compartment. Both compartments have separate doors (see-through or opaque) and act as two independent temperature zones. The refrigeration compartment temperature is programmed between 2-12oC, whereas the freezer temperature is set between -10oC and -30oC. The system contains an LED display, alarm and temperature control systems, door lock, etc.
The energy-efficient upright, under-counter, ultra-low temperature and fridge-freezer combination models are specially designed to fit your laboratory needs. The exclusive units with proper shelving, temperature monitoring system, LED display, door locks, and alarm systems provide a complete storage solution to your experimental needs.
Biological Product/Specimen Storage
Freezers and fridge-freezer combinations are specifically designed for the long-term storage of biological samples like stem cells, vaccines, enzymes, microbial cultures, cell lines, and tissues. The blood bank and hospital freezers and combos ensure a reliable cold chain—efficient vaccine and pharmaceutical storage in laboratories and pharmacies.
Cryopreservation of Mammalian Cells
Cryopreservation is routinely used in academic, industrial, and clinical research. It is mainly employed for the long-term storage of pluripotent stem cells, spermatozoa, embryos, and conventional cell lines. Moreover, cryopreservation applications include freezing cells or organelles, cryosurgery, food sciences, biochemistry, molecular biology, ecology, and other animal lab applications like in vitro fertilization, artificial insemination, and bone marrow transplants (Jang et al., 2017).
Several cryoprotective agents (CPA) are added to the cells during the process to prevent freezing and ice crystal formation in biological specimens. Glycerol and DMSO are the most common CPAs. However, Akiyama et al. (2019) described a CPA-free method for the cryopreservation of mammalian cells by using ultrarapid cooling using inkjet cell printing, which they called “super flash freezing (SFF).” While comparing this technique with conventional cryopreservation, they suspended the cells (Mouse NIH 3T3 fibroblast cells and rat myoblast cell line C2C12) in a culture medium containing 10% v/v DMSO. They deposited the suspension in a cryovial and subjected it to slow freezing. They placed the samples collected in a freezing vessel in a ULT freezer set at -80oC for slow freezing. The researchers concluded that the CPA-free method could be used as an alternative cryopreservation technique to avoid cytotoxicity and potential side effects of CPAs on the cellular state.
Strengths and Limitations
Each type of freezer and combos have its strengths and limitations. For instance, under-counter freezers and fridge-freezer combinations are lab space savers with less storage space. The accurate temperature monitoring systems and alarms present in freezers and combos help maintain the samples under controlled conditions. Freezing is the most efficient method for the long-term storage of biological samples. It prevents specimen cross-contamination with other cell cultures and reagents. Moreover, freezing stops the metabolic processes in biological samples, significantly reducing the risk of genetic or morphological changes. Cryopreservation of samples allows the researchers to save money, improve experimental reproducibility, and protect irreplaceable sample stocks.
Although preserving biological specimens at extremely low temperatures (up to -80oC) using ULT freezers is the “gold standard” for specimen storage, the disadvantages of freezing the samples are irrefutable. For instance, CPAs used during cryopreservation can result in cytotoxicity and have potential side effects on cellular systems. Moreover, freezing damages cell membranes and decreases samples’ “histological readability.” Also, actively reproducing cells for more extended periods can alter the gene expression and disturb the homogeneity of cell cultures, ultimately endangering reliable research results. Freezers and combos might be a space saver, yet they are too costly and consume too much energy. However, the researchers have now come up with new energy-efficient models to resolve this “energy efficiency paradox.”
- Laboratory freezers are the refrigerated cabinets employed for storing biological samples and reagents in animal laboratories at temperatures ranging from -40oC to 10oC.
- The purpose of freezing biological samples is to store them for long-term usage without damaging their structural and metabolic integrity.
- Cell storage serves as an “insurance policy” in cell shortage, contamination, or experiment failure.
- Chest freezers have a top opening instead of a front door. They offer ample storage space for animal research facilities.
- Ultra-low temperature (ULT) freezers preserve frozen specimens and vaccines for biological labs and pharmacies. They maintain temperature between -40oC and -86oC.
- Under-counter freezers are the best storage solution for labs with less space.
- Upright freezers are common in research laboratories and medical institutions. The purpose of upright freezers is to maximize temperature consistency.
- Fridge-freezer combinations have two separate compartments, a refrigeration compartment, and a freezer compartment.
Akiyama, Y., Shinose, M., Watanabe, H., Yamada, S., & Kanda, Y. (2019). Cryoprotectant-free cryopreservation of mammalian cells by super flash freezing. Proceedings of the National Academy of Sciences, 116(16), 7738-7743.
Jang, T. H., Park, S. C., Yang, J. H., Kim, J. Y., Seok, J. H., Park, U. S., … & Han, J. (2017). Cryopreservation and its clinical applications. Integrative Medicine Research, 6(1), 12.