The integrity of biological samples are a crucial component of basic and clinical research. The capacity and quality of biobanks and biorepositories has grown in recent years, making them treasure troves of biological information. Entire studies are conducted using samples in such biobanks, without having to collect additional—and sometimes rare—samples from patients. Biobanks are also important for longitudinal studies of patients undergoing long-term treatment of illnesses such as cancer, preserving original tumor samples as a valuable snapshot in time that may someday help to cure it.
Besides traditional samples of solid tissues such as tumor biopsies, biobanks are increasingly storing liquid biopsies—patient samples such as blood, plasma, serum, urine, or less commonly, saliva or breath condensate. Liquid biopsies are relatively non-invasive, less painful, and less expensive to acquire. In addition, the presence of circulating tumor cells and cell-free RNA in blood have generated interest in using them as cancer biomarkers.
Preserving both liquid and solid biospecimens requires careful sample collection and processing, attention to proper storage considerations, and the tools to track the histories of samples accurately and efficiently. Here’s a look at some important issues in biobanking today.
Sample quality control
Incorporating elements that maintain high sample quality is one of the most important things labs can do. “The ultimate goal is to have the highest-quality samples that will provide useful data, regardless of when a sample is retrieved in the future,” says Paul Wylie, head of applications at TTP Labtech, which works with liquid biospecimen storage in biobanking. “This means that every step of the process should be optimized following best practice guidelines when they are available.”
Image: Scientific workflow from TTP Labtech.
Standard operating procedures go a long way here, as well as tracking all steps in the sample processing workflow, and working with samples as quickly as safely possible. Wylie recommends quality control checks throughout all stages from collection to storage, to check for sample quality. “Analytical methods are becoming more sensitive and therefore sample quality becomes even more important,” says Donat Elsener, director of sales and marketing at Hamilton Storage, whose customers work mainly in epidemiological studies, such as newborn screening and disease-based biobanks, as well as forensics.
Sample storage volume
Elsener notices a general trend toward storing samples in smaller volumes. Aliquoting important samples into smaller single-use volumes helps to preserve the overall sample, compared to larger volumes that are repeatedly accessed and removed from the controlled environment. “Strategies such as storing numerous smaller aliquots to enable a single-shot use approach for each aliquot can be extremely effective compared to the approach of using a single large aliquot to freeze/thaw several times throughout its storage lifetime,” says Wylie.
Yet not all samples can be stored this way. “The rise of analytical methods, such as for circulating tumor cells, creates a need for large-volume plasma samples,” says Elsener. Indeed, the increasing interest in liquid biopsies may drive the development of new storage solutions for larger volumes of liquid samples.
Sample storage conditions
The most common storage equipment found in most biobanks and biorepositories is the -80°C freezer (typically, temperatures can be held a few degrees lower), which are among Panasonic Healthcare’s biggest selling items, according to their product and business intelligence specialist, Kenan Moss. Panasonic Healthcare’s Ultra Low Freezers, for example, store items at -86°C. These are particularly useful because in addition to long-term storage, they have a place for intermediate storage as well.
Biocompare’s Lab Refrigeration Search Tool
Find, compare and review refrigeration
equipment from different suppliers Search
Some freezers incorporate back-up safety measures to preserve samples. Panasonic Healthcare’s Twin Guard series have dual compressors that work independently, so that if one should ever fail (which is highly unlikely), the samples can be kept at -70°C or colder, while the other compressor is repaired. Panasonic Healthcare also offers an eco-friendly ENERGY STAR Certified ultra low temperature freezer, the VIP ECO, that uses natural refrigerants, which Moss notes is a trend among companies in the field. For longer-term storage, cryopreservation units that store samples at about -150°C are the best option.
A crucial concern when storing tissues—and especially liquid samples—is crystallization.
A crucial concern when storing tissues—and especially liquid samples—is crystallization. “The aqueous environment is one of most important considerations of dealing with liquid specimens because when the water in the sample freezes, it expands and creates ice crystals that can damage the integrity of the sample,” says Moss. Being aqueous by nature, liquid samples in particular pose this storage challenge, but it’s less of a concern at the lower cryopreservation temperatures, especially with rapid cooling and thawing. “Cryopreservation is ideal for cells due to the fact that the glass transition temperature of water is -137°C,” he adds. “Below that temperature water freezes amorphously, and therefore doesn’t create crystals, which can damage cells and tissues.”
For cryopreservation, and even for storing biospecimens in -80°C units, using a cryoprotectant like glycol or DMSO can help to protect samples from crystallization. “Glycol affects the water surrounding the tissue sample, lowers the freezing point, and helps to mitigate the effects of ice crystals,” says Moss. “Some cryoprotectants will in fact dehydrate your tissue sample so there's less water inside to crystallize.” After thawing, the cryoprotectant can be separated out from the sample.
Sample tracking and management
Most biobanks use some sort of laboratory information management software (LIMS) tool for keeping tracking of where a sample is stored (for example, which inner storage box inside which -80°C freezer), as well as the history of the sample (for example, date collected, collection protocol used, patient information if relevant, and any sample processing and analysis performed). A wide variety of LIMS systems are available today, and can be purchased from vendors, found as open-source software, or developed in-house.
The variety in LIMS systems reflects the range of solutions sought by individual labs with unique sets of needs. “We see that these tools are absolutely necessary, but also that there doesn’t seem to be any single solution that is appropriate for all, or any emergence of a clear market leader that starts to bring some commonality,” says Wylie. Because of this, TTP Labtech tries to make its systems capable of interfacing with any LIMS system.
Along with tracking the whereabouts of samples, it’s helpful if the LIMS system can store analytical data as well. “Comprehensive data annotation with the samples is key for success,” says Elsener. On the other hand, this may entail consideration of patient privacy as well. “There is the added complexity of managing sensitive patient-related data separately from the specific sample data,” says Wylie.
The best LIMS system is any one that a lab can use to keep samples organized and well-preserved, so that researchers can easily find each sample, and quickly see its collection data and subsequent history. With these tools at hand, researchers can feel secure in the knowledge that their most important biospecimens will be safe and sound.
Image: The tube picking module in Hamilton Storage systems enables cherry-picking of specific user-requested samples while maintaining sample integrity of all stored samples. Image courtesy of Hamilton.