Every drop counts — harnessing blood's analytical value

Blood tests are one of the most widely performed methods to assess the general health of an individual, offering a wide range of insights from a relatively easy and painless procedure. The vast information within the blood is increasingly being explored to help diagnose or monitor a wide range of health-related issues, such as brain injuries, infections and even cancers.^1-3 The separation of blood into its main constituents is traditionally done manually — a slow and tedious method that is not standardised — putting laboratories under ever-increasing pressure to maintain accuracy in the face of heightened demand. This article highlights a novel approach that uses automation to precisely detect liquid-liquid interfaces, allowing the clean separation of blood at higher throughput compared to manual techniques.

The vital constituents of blood

Separating blood into its three main components — plasma, the buffy coat (comprising leukocytes, lymphocytes and platelets) and erythrocytes — via density-gradient centrifugation is a vital step in many research and clinical procedures, forming the foundation of numerous downstream applications. Although all three are under the microscope across laboratories worldwide, the first two are emerging at the forefront of ground-breaking research for various clinical applications.

Buffy coat

Although the buffy coat only accounts for less than one per cent of a whole blood sample, it is a crucial constituent for medical research and diagnostics, given its high concentration of white blood cells and platelets. Many laboratories also prefer to extract genomic DNA from the buffy coat — instead of whole blood — as researchers can purify it in large amounts using only a small sample. This is critical for genome-wide association studies, and to ensure that enough genetic material is stored in biobanks for future research in genomics and proteomics, as well as multiple disease areas, including oncology, neurodegenerative diseases and metabolic disorders. Furthermore, the buffy coat can also be used to detect and quantify malaria,⁴ as well as other blood parasites, such as Haemoproteus, Trypanosoma and microfilariae.⁵

Plasma

Plasma is the main constituent of blood, and it is poised to play a central role in the future of oncology. A conventional tissue biopsy still remains the gold standard in the diagnosis of many malignancies, but this technique comes with many drawbacks, including its invasive nature and difficulty in applying to all cancer types and patients. These challenges are largely non-existent with liquid biopsies, where cell-free DNA (cfDNA) in the blood can be analysed to provide a comprehensive view of tumour heterogeneity, potentially serving as a diagnostic, prognostic and predictive biomarker.⁶ Further validation of cfDNA in oncological applications is required before it becomes a standard in clinical practice,⁷ with advancements in automation and high throughput screening essential in enabling researchers to classify cfDNA precisely and rapidly in large patient cohorts.

Complexities of separating blood samples

The widespread use of blood in research and diagnostics is placing enormous pressure on laboratories to keep up with the demand. Traditional manual separation techniques, however, are slow and prone to human error, regardless of the technician’s experience. For example, the buffy coat forms an incredibly thin layer between plasma and erythrocytes, but isolation — usually performed manually with a Pasteur pipette — is prone to contamination of the latter, due to their size and abundance in a whole blood sample. Even when automation is available, detecting liquid-liquid interfaces following centrifugation can be challenging, as barcodes and labels can interfere with sensors. This again slows down processing times when labels need to be removed, potentially resulting in a loss of chain of custody. These complications prompted Tecan to develop an innovative approach to liquid separation, which saves time and improves accuracy in laboratory workflows.

Introducing Phase Separator™

Phase Separator from Tecan is a significant advancement in liquid separating technology, offering precision and speed to streamline workflows and improve efficiency in both research and clinical laboratories. It is a unique, pressure-based technology of the Air Flexible Channel Arm™ (Air FCA) on Tecan’s flagship liquid handling platform, the Fluent^® Automation Workstation. This novel method addresses the critical challenge of detecting liquid-liquid interfaces and effectively separating neighbouring phases, while avoiding the risk of contamination, making it ideal for separating plasma or the buffy coat in centrifuged blood samples.

Phase Separator can achieve remarkable speeds working in either tubes or plates by combining phase detection with the pipetting action. Processing speed is further enhanced when all eight channels on the Air FCA are used in parallel — enabling the aspiration of plasma from 24 tubes of centrifuged blood in under 10 minutes* — and twice as fast again on dual-arm systems. These benefits come with no loss of bench space and no additional equipment to maintain, while the technology detects liquid levels with pinpoint precision inside the tube or plate, so there is no interference from barcodes or other markings.

Keeping your finger on the innovative pulse

Biological samples can now be processed faster, more accurately and even more efficiently than with previous methods, translating to productivity gains and cost savings for laboratories. This will be especially important in the rapidly evolving field of liquid biopsies — benefiting disease diagnostics and monitoring — as well as broader research applications, where it will help to accelerate discoveries.

For further information about Tecan's Phase Separator, please visit www.tecan.com/phase-separator.

*Timing is volume dependent. Time given for separation volumes of 5 mL.

_{1. Casanova-Salas I, et al. Quantitative and Qualitative Analysis of Blood-based Liquid Biopsies to Inform Clinical Decision-making in Prostate Cancer. Eur Urol. 2021;79(6):762. doi:10.1016/J.EURURO.2020.12.037}

_{2. Park S, et al. Blood Test for Breast Cancer Screening through the Detection of Tumor-Associated Circulating Transcripts. Int J Mol Sci. 2022;23(16). doi:10.3390/IJMS23169140/S1}

_{3. Sohn E. Diagnosis: Frontiers in blood testing. Nature. 2017;549(7673):S16-S18. doi:10.1038/549s16a}

_{4. Abeje G, et al. Comparison of capillary, venous and buffy coat blood samples in detecting Plasmodium species among malaria suspected patients attending at Hamusite health center. A cross-sectional study. BMC Infect Dis. 2021;21(1). doi:10.1186/S12879-021-06290-6}

_{5. Chagas CRF, et al. The buffy coat method: A tool for detection of blood parasites without staining procedures. Parasit Vectors. 2020;13(1):1-12. doi:10.1186/S13071-020-3984-8/FIGURES/3}

_{6. Volckmar AL, et al. A field guide for cancer diagnostics using cell-free DNA: From principles to practice and clinical applications. Genes Chromosomes Cancer. 2018;57(3):123-139. doi:10.1002/GCC.22517}

_{7. Stawski R, et al. Current trends in cell-free DNA applications. Scoping review of clinical trials. Biology (Basel). 2021;10(9). doi:10.3390/BIOLOGY10090906/S1}