Cell purification: a new challenge for biobanks.

Performing '-omics' analyses on heterogeneous biological tissue samples, such as blood or bone marrow, can lead to biased or even erroneous results, particularly when the targeted cells and/or molecules are present at relatively low percentages/amounts. In such cases, whole sample analysis will most probably dilute and mask the features of the cell and/or molecules of interest, and this will negatively impact the results and their interpretation. Therefore, frequently it is critically important to have well-characterized and high-quality purified cell populations for the reliable detection of subtle variations in their specific features, such as gene expression profile, protein expression pattern and metabolic status. Biobanks are technological platforms which aim to provide researchers access to a large number of high-quality biological samples and their associated data, particularly to support high-quality scientific and clinical research projects, and such projects will benefit enormously by having access to high-quality purified cell populations or their biological components (e.g. DNA, RNA, proteins). Therefore, a clear opportunity exists for preparative cell sorting techniques in biobanks. Although multiple different cell purification approaches exist or are under development (e.g. cell purification techniques based on cell adherence, density and/or cell size properties, methods based on antibody binding as well as new lab-on-a-chip purification techniques), the choice for a specific technology depends on multiple variables, including cell recovery, purity and yield, among others. In addition, most cell purification approaches are not well suited for high-throughput (HT) purification of multiple cell populations coexisting in a sample. Here we review the most (currently) used cell sorting methods that may be applied for sample preparation in biobanks. For the different approaches, technical considerations about their advantages and limitations are highlighted, and the requirements to be met by a HT cell sorting technology to be used in biobanks are also discussed.