Sample Storage Challenges
As the number of samples increases and smaller biobanks consolidate, accurate tracking, storage, and retrieval become vital issues. Many organizations still store and retrieve samples manually from liquid nitrogen (LN2) tanks or -20ºC or -80ºC standalone freezers, an approach that is fraught with difficulties.
The first issue is the maintenance of sample quality because degraded samples may compromise assay results. Storage temperature should remain stable to ensure sample integrity. However, the constant opening and closing of a manual door creates continuous temperature fluctuations and freeze-thaw cycles.
A door held open on a manual freezer for even a short period of time can result in a significant temperature rise. Constant frost buildup makes samples harder to locate and must eventually be removed, which further exposes stored items to temperature fluctuations. Additionally, air expands by approximately 50% when its temperature rises from -80ºC to 20ºC. This creates an air draft in an upright freezer, which accelerates more fluctuations.
Data gathered by Hamilton Storage Technologies shows that the temperature of samples taken from -80ºC storage to ambient conditions increases at an average of 21.5ºC per minute (Figure 1). Holding a manual freezer door open for more than one minute can raise the temperature to above -60ºC. This can happen countless times over the lifetime of a sample stored and retrieved manually. Accumulated temperature rises above this level are believed to damage the integrity of many types of biospecimens.
Another notable challenge is the staff size needed to run a manual biorepository. For instance, the Rutgers University Cell and DNA Repository utilizes around 100 technicians to perform biorepository services and store samples for a fully functioning biobank that consists of 45 LN2 tanks and 90 chest freezers. The labor costs of running a manual biobank are high, and as biobanks continue to grow in size, manual access becomes increasingly more complex and difficult to manage accurately.
Additionally, accessing samples in manual freezers can consume significant amounts of the staff’s time. The Table shows the time required for each of the steps from storage to retrieval, comparing the use of a manual freezer to an automated storage system. Many manual biobanks encounter similar issues, according to assistant director Melissa Rawley-Payne from the CTSI Biorepository at the University of Florida. In some cases, she believes it could take hours for samples to be retrieved from freezers in some of the nonautomated tissue banks across the campus.
Sample security is another critical issue in any facility that is operating under regulatory controls, maintains potentially dangerous chemicals or infectious agents, or that maintains associated donor data with the samples.
In order to comply with various regulations, facilities must produce chain of custody reports and audit trails showing who had access to the samples and what they did with them. The lack of such security measures can even put the public at risk, as was the case in 2001 when anthrax was retrieved from an unsecured lab.