In science laboratories, researchers know the value of keeping samples frozen for long periods of time. Nonetheless, many scientists don’t give much thought to the features of a laboratory freezer. Such a lackadaisical attitude surely changed for some scientists after they heard about the recent freezer malfunction at McLean Hospital outside of Boston, Massachusetts. That freezer contained brain samples to be used for autism research conducted by the Harvard Brain Tissue Resource Center.
Given that accident, it’s not surprising that an increasing trend in laboratory freezers involves reliability. At Reflect Scientific (Orem, UT), principal scientist Boyd Bowdish, Ph.D., agrees. That’s why, he says, “our system is a mission-critical design, so every point is redundant.”
Trends in tracking
“Anyone with a freezer in a lab has lots of money tied up in the samples,” says Larry Miller, account manager at RURO (Frederick, MD). “The trend we’re seeing is people finally spending some of their money to fine-tune sample tracking.” He adds, “After a short time, most people lose track of what’s in their freezers.”
Although a lab might track lab samples in a spreadsheet program, Miller thinks that’s not enough. “The transition and turnover in labs makes it almost an insurmountable task,” he says. As a result, he notes, “people are getting tired of wasting time searching for their frozen samples. You can literally have thousands of samples with little or no information about them.”
Miller points out that people can end up unsure about many things: what a sample is, how old it is, who put it in the freezer. To track samples over the years without even opening the freezer door, Miller recommends a radio frequency identification (RFID) system that identifies all the samples and keeps track of their background.
Users also want freezers that expend less energy. As Bowdish says, “Users want sustainability on the environmental-responsibility front.” He adds, “At the point of use, our freezing system eliminates 90 percent of the electrical power that a mechanical freezer uses.” The Reflect freezers reduce electric use by cooling with liquid nitrogen and using a technique that requires no compressors. Overall, says Bowdish, the efficiency of a freezer depends on the insulation properties and the cooling medium. The total freezer-related use of energy also goes beyond the device. “A traditional system needs air conditioning in the room where it’s located,” says Bowdish, “because of the heat from the freezer.” He adds, “Our system, at any time, uses a maximum of 500 watts, so our carbon footprint is very small at the point of use.”
The environment around a laboratory freezer can also be improved. “With mechanical freezers,” says Bowdish, “the safety problem is not the cold so much as it is the noise. They can be very loud.” To handle that lab-safety issue, try a liquid-cooled freezer with a pump, which won’t make as much noise. Moreover, the noise from a freezer can even be muffled, and the remaining noise can be piped outside.
Cleaning a lab freezer can also create some problems. The extreme cold alone requires care. Plus, some lab freezers ice up, which can create large cakes of ice that take up space that could be used to store samples. Some samples can even get trapped in the ice and need to be chipped out. The freezers from Reflect create only a frozen powder that can be wiped out. “You still need to be careful, though, because it’s cold,” Bowdish says.
Ramping up reliability
Reliability covers lots of ground in terms of laboratory freezers. Says Bowdish, “Users don’t want the freezer to break. They want reliability and consistency, so our freezers maintain an internal variation of +/– 3 degrees Celsius at any point in the freezer.”
To keep the environment consistent inside a freezer, its recovery time also matters. That is, when someone opens a freezer’s door, how long does it take the temperature to equilibrate to the set point throughout the device? “After a one-minute door open and close,” says Bowdish, “it takes less than five minutes—typically just 90 seconds—for our freezers to equilibrate.”
At the Uppsala Biobank in Sweden, director Anna Beskow, Ph.D., also looks for ways to improve the use of freezers. “We use freezers for biobanking,” she says, “and they are manual –80.” She adds, “We are also now buying an automated –80 freezer.” The reason for the change from manual to automatic at the Uppsala Biobank arises from the storage format. As Beskow explains, “We store our samples in microtubes in a 96-plate format. The plate has a 1D-code on one side and 2D-codes at the bottom.” Each of these tubes contains 200–250 microliters of sample. “It’s difficult and almost impossible to manage repicking and withdrawals of those tubes manually with secure traceability; therefore, we need automation,” Beskow says. “Our backup samples will still be stored in manual freezers. From each primary sample we get eight aliquots of these, and we aim to store one to two aliquots in the automated freezer and the rest in manual freezers.” She adds, “So we might still buy more manual freezers.”
As the scenario at the Uppsala Biobank reveals so clearly, different research situations call for different features in laboratory freezers. It’s not always just about the temperature, because many other details come into play. No matter what, though, users require freezers that stay at the desired temperature for years. No one wants to see unnecessary accidents destroying priceless samples.