Cold storage is essential to any laboratory with a requirement to preserve precious samples. Encompassing short-term 4°C refrigeration all the way through to -156°C air-phase cryogenic preservation, a wide range of cold storage solutions exists to keep research programs on track. But what are the key features you should be looking for when selecting a cold storage solution for your lab? Here, we provide an overview of the different types of cold storage solution available and note some important questions you should ask.
Types of cold storage solution
Cold storage solutions can broadly be categorized according to the temperature range at which they operate. Pharmaceutical refrigerators typically function at 2°C to 8°C, whereas biomedical freezers have a temperature range of -10°C to -30°C. These laboratory mainstays are complemented by ultra-low freezers that operate at temperatures of -40°C to -86°C, and various -156°C air phase cryogenic storage solutions that minimize the need for liquid nitrogen.
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Download this ebook now to learn more about what to look for in a reliable cold chain product for clinical and research use, as well as in biotech and life science industry environments.The choice of cold storage solution will largely be dictated by the availability and temperature sensitivity of sample material and the length of time for which it will be preserved. While pharmaceutical refrigerators are ideal to maintain samples over the short term, usually days or weeks, irreplaceable material is more commonly stored in an ultra-low freezer or preserved cryogenically for months or even years. Most laboratories employ several cold storage solutions in parallel to meet a variety of needs.
Key features of effective cold storage solutions
Irrespective of the operating temperature, effective cold storage solutions should demonstrate several key features. Primary among these is a uniform interior temperature since this is critical to avoid compromising sample integrity. For instance, where a refrigerator reaches lower temperatures toward the back of a shelf, samples that are in contact with the refrigerator wall may inadvertently become frozen. With freeze-thawing widely recognized to be damaging to protein/cellular structure, this should be avoided at all costs.
Another important requirement of cold storage solutions is that they provide precise temperature control accuracy. This is usually achieved by linking a temperature sensor to a cooling device such as a fan in order to maintain the storage temperature at a set level. Digital systems offer the advantage of a visible control panel that enables users to quickly assess instrument performance. They are readily combined with wireless monitoring solutions for a permanent record of storage temperature over time.
Cold storage solutions should also provide fast temperature recovery after door opening, especially in laboratories where ambient conditions may fluctuate widely throughout the day. High ambient temperatures can introduce the potential for generating misleading results due to unforeseen sample degradation, making it vital to minimize the effects of room temperature on storage conditions. Moreover, with cold storage solutions often being a shared resource among laboratory users, fast temperature recovery is essential to withstand the inevitably high frequency of door opening.
Finally, effective cold storage solutions will employ measures that avoid the impact of power fluctuations. These include the ability to maintain a set temperature for a period of several hours following a power outage (provided the door remains closed), and the option for connection to a back-up power supply. In many instances, laboratories will have systems in place that prevent critical equipment being affected by power outages (for example, a generator may have been installed), but where this is not the case it is sensible to confirm the tolerance of a cold storage solution to a sudden loss of power.
Selecting a suitable cold storage solution
Several factors are of note when choosing a cold storage solution. Second only in importance to the operating temperature is size. Not only must the cold storage solution fit the available lab space, leaving room for air circulation to prevent over-heating, but it must also have sufficient capacity to hold the quantity of material that will be placed inside it. Overloading a refrigerator or freezer invariably results in temperature fluctuations, not least due to the door being left open for extended periods while researchers try to locate sample material.
Under-counter refrigerators and freezers are hugely popular, providing researchers with easy access to samples without the need to change PPE and enter another lab. Combination refrigerator/freezers are also widely used, especially in labs where under-counter space is already taken up by other bulky equipment such as incubators or orbital shakers. With a range of sizes and configurations available, combination refrigerator/freezers can be a good choice for labs where large numbers of samples will be stored.
Because ultra-low freezers are usually employed to store samples that are used infrequently, and because they typically have different electrical requirements to under-counter and combination refrigerator/freezers, they are often sited in a dedicated room. Here, space may be less limited, making both upright and chest freezers an option. Choosing between these is largely down to the instrument footprint and user preference; with the correct racking system in place, both formats allow for easy access to samples.
One last consideration, as already mentioned, regards whether the cold storage solution will be linked to an independent lab monitoring system. By using an independent sensor to track temperature over time and logging data in the cloud server, lab-monitoring systems provide a real-time alert when a temperature deviation from set levels may be a cause for concern. With the need to access data remotely being fueled by the COVID-19 pandemic, lab-monitoring systems are seeing significantly increased use, and they have already demonstrated widespread utility as an effective means of protecting sample material.
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