From Whole Blood Collection to Long-Term Fraction Storage
In recent years, new research insights and breakthroughs have created demand for studies based on larger numbers of human samples. Facilities including hospitals, private research facilities, and huge government-owned biobanks, biorepositories of patient samples for research purposes are springing up all over the world. One Hamilton Robotics customer plans to collect and store blood fractions from six million donors, which requires processing blood from several hundred subjects per day. The samples in this biobank will be used to study the epidemiology of cardiovascular diseases, diabetes, cancer and hypertension.
Whole blood collected for research purposes is typically separated by centrifugation into three fractions plasma, buffy coat and red blood cells. Whole blood can be collected, shipped and fractionated later at a central site, which requires only one processing station with a standardized procedure. However, shipping time is variable and the shipment conditions for whole blood need to be carefully controlled. Alternatively, whole blood can be processed close to the collection site and then shipped and stored as fractions. This strategy provides greater control over the process and monitoring of blood fraction generation. Many biobanks are now striving to process the blood within two hours of collection and then shipping the fractions on dry ice. This method has advantages over shipping whole blood samples that may be subject to freezing-related cell disruption. As specifications for research projects become more precise, many are trying to standardize the collection window by processing all samples within the same amount of time after collection. When whole blood is shipped and stored for later fractionation, this kind of consistent collection window is impossible to create.
It is also advantageous to fractionate at the collection point because many biorepositories do not need all three fractions. Most are interested in the plasma, and some only want plasma and buffy coat the fraction that contains most of the white cells and platelets. The buffy coat is the fraction used to extract DNA from mammalian blood samples and forms a thin layer between the plasma and red blood cells, making up less than one percent of the total centrifuged blood volume. Because red blood cells do not contain DNA, the fraction containing them is not useful to many research projects.
The trend toward processing whole blood samples close to collection magnifies the need for ways to increase process efficiency and throughput at these sites what is called a distributed approach. Aliquoting the fractions into storage tubes, traditionally done manually, is challenging because it s difficult to physically pinpoint the exact location of each fraction. Because these samples are highly viscous, care must be taken to minimize mechanical shearing forces during pipetting to avoid damaging the white cells. The quality of fractionation with manual pipetting varies widely by individual lab technician and it s slow. Therefore, much attention is being directed to developing systems that can accurately automate the very tedious manual pipetting process, enabling the efficient and accurate processing, shipping and storage of large numbers of samples. Hamilton Robotics has developed a new highresolution, camera-based system that recognizes the exact location of the fractions in a centrifuged donor tube and allows the accurate aliquoting of the plasma, buffy coat and red blood cells. The camera channel uses one arm on the Hamilton MICROLAB STARline* Automated Liquid Handling Workstation deck. The arm with the camera channel has the same independent y-axis (forward/backward) flexibility as the independent pipetting channels.
Dedicated software controls the camera s imaging settings and visualization interpretation. The system takes a picture of four tubes at a time on the deck of the workstation and visualization software interprets the images and generates data used to direct the pipetting and labware transfer functions of the workstation. A gradient search technique algorithm is incorporated in the software to convert digital pixels into physical dimensions and use them to create z-height pipetting specifications, which it communicates to the STARline workstation. The VENUS instrument control software tells the robot the exact depth at which the different fractions, including buffy coat, can be pipetted.
All of the tubes and tube carriers are marked with unique identifiers and bar codes link to collected patient information so the data and the sample stay together. When samples will be stored immediately after processing, the Hamilton Rack Runner Robot picks up the tube racks and delivers them to a Sample Access Manager (SAM) -80 C storage system (Hamilton Storage Technologies), where exact locations are recorded via bar code reader and the information integrated with the lab s LIMS for complete sample tracking. With this sophisticated sample tracking, any tube can be precisely located and retrieved at any time. This approach to sample storage maintains a documented chain of custody and prevents problems attributed to human error.
Workflow Steps to Improve the Outcome of Whole Blod Fractionat ion and Storage