Accessing pure samples of viable cells is integral to effective clinical treatments and biomedical research initiatives. Cell washing removes unwanted components present in cell suspensions —such as residual plasma, platelets, and red blood cells—to improve the quality of the sample.
Like dead cell and debris removal, cell washing purifies the sample for improved downstream analysis. Broadly, cell washing is any process that involves the washing and separation of cells from interfering substances, including dead cells, debris, and other cell populations.
The cell washing procedure can be modified to fit numerous scientific applications across both clinical and research settings. By adjusting the buffers used, the starting cellular material, the volume of fluid processed, and the number of washes, the goals and specifications of the cell washing steps can vary greatly.
To start a basic manual protocol, add a buffer, such as a saline solution, to the cells. Next, centrifuge the sample and discard the supernatant. Then, resuspend the cell pellet for cell counting and downstream use.
Cell washers are specialized laboratory instruments programmed to fit multiple applications. They are designed to wash cells, separate them from their buffer solutions, and prepare them for downstream assays and analysis. Composed of a washing chamber, a set of fluid distribution valves and tubes for the delivery and removal of waste, and a control module, automated cell washers are critical in research and clinical settings.
Tubes of cells suspended in their original buffers load into the cell washer, and the washing buffer flows continuously through the valves and samples. As the washing buffer eliminates contaminants or unwanted substances from the cells, it expels them from the washing chamber as waste.
Thermo Fisher Scientific is a popular producer of cell-washing processing solutions such as the Rotea Counterflow Centrifugation system. Specifically designed for cell therapy manufacturing applications, the Rotea system is a closed system that implements counterflow centrifugation to separate contaminating blood components, such as red blood cells, platelets, and some white blood cells, while minimizing the loss of cells of interest.
Cell washing is an essential component of various applications, such as research and development projects. Clinical and research laboratories utilize cell washing in distinct ways. Commonly, cell washing is used to remove contaminants or unwanted substances from cells for isolation and downstream analysis. Removing unwanted cells improves the purity of the sample and the quality of assay performance, as seen in techniques like PCR or flow cytometry.
Cell washing is also used during antibody labeling to remove excess or unbound antibodies or reagents from the cells for increased specificity and reduction of conflicting “noise” that could disrupt proper testing or implementation outcomes.
Another common utilization of cell washing procedures is blood processing within blood banks for transfusion, research, and storage. Cell washing reduces inflammatory transfusion reactions, such as transfusion-related graft-versus-host-disease. Additionally, removing unwanted cells prolongs the shelf life and storage capacity of blood samples by protecting against storage lesions. In other words, cell washing improves transfusion safety and enhances the quality and longevity of desired cells.
Cleansing the blood of red blood cells and platelets enables samples to maintain their oxygen-carrying and clotting abilities essential to transfusion success, thereby allowing for longer storage periods. Major diagnostic testing facilities also include cell washing in the sample preparation of various bodily fluids to improve the accuracy and reliability of diagnostic results. Cell washing can be a crucial step in several applications where the purity and quality of isolated cells are critical for performance.
Red blood cell (RBC) contamination in samples can impact the test results during downstream analysis. By clouding and obfuscating the cells of interest, RBC contamination conflicts with downstream reagents, such as primers and buffers, which can compromise the testing results.
In flow cytometry applications, RBC contamination can interfere with the viability dye of the target cells being analyzed, causing inaccurate viability measurements. Red blood cells also contribute to blood sample degradation by releasing harmful by-products that accumulate as the blood is stored over time, resulting in a loss of essential performance functions and overall cell viability due to oxidative stress. Cell washing protects the integrity and quality of a sample by eliminating excess cellular material and extending its shelf life and effectiveness.
All companies that process and wash cell solutions for clinical applications must comply with good manufacturing practices (GMP). Due to the widespread need for commercializing clinical and research applications requiring washed cells, cell washing protocols must be affordable and scalable while maintaining high-end product quality. GMP compliance ensures the end product is consistent, pure, and of high clinical quality.
Unwanted contamination within a blood sample, such as red blood cells, dead cells, and debris, can interfere with cell isolation and separation. Residual platelets and other cell debris decrease the purity in a population of isolated cells, confounding the results of further applications of the isolated samples, such as flow cytometry, cell culturing, and molecular assays.
By washing the cells of these impurities, the cell separation process yields more robust and pure final products. The washed and isolated cell suspension sample will contain a homogenous cell suspension with increased viability for successful transplantation or engraftment applications.
Akadeum’s kits are compatible with upstream cell washing technology to prepare cell samples for optimal performance. By selecting for unwanted cells rather than cells of interest, the negative selection microbubble kits leave isolated cells in their natural state: