Flow Cytometers
Focus on high throughput, precision, and sensitive technologies in 2020
The past decade has seen a swift improvement in flow cytometry, expanding the frontier for its applications. 2020 has prompted use of such high precision and sensitivity techniques in diagnosis, therapeutics and research of COVID-19 and other diseases.
Flow cytometry is a powerful, widespread and flexible technology that delivers high-content data about multiple characteristics of single cells and particles. This laser-based technology, used to count and sort cells, detect biomarkers and engineer proteins, involves suspending the cells in a stream of fluid and passing them by an electronic detection system. As a robust technique, flow cytometry system has versatile utility in research and clinical laboratories for chromosome analysis, cancer diagnosis, protein expression, DNA and RNA quantification, multidrug resistance, and measuring enzyme activity. Immunophenotyping by flow cytometry plays a central and very relevant role in many of monoclonal antibodies and other cell therapies for cancer.
Despite the clear advantages of the high throughput, multiparameter functionality of flow cytometry, it is handicapped by the immense output of highly complex data. Significant advancements have been introduced over the last years to provide reliable systems and software to interpret this data correctly and improve standardization in assay as well as instruments. Combining flow cytometry with futuristic technology including artificial intelligence and microfluidic-based devices is pushing forward the progress in integrated and miniaturization of analytical devices at the point-of-care.
Flow cytometry assays aid in the battle against COVID-19
Researchers in France published a study demonstrating the sensitivity of a rapid flow cytometry assay that could be used to screen for COVID-19 causing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The assay is designed to detect the upregulation of whole blood monocyte CD169, a marker of viral infections. This rapid assay has shown more sensitivity than the currently used method and is less likely to produce false-negative results, especially among early and asymptomatic patients.
According to the research team, screening for monocyte CD169 upregulation could reduce the load on health systems, slash down overall costs, and make sample collection easier for a significant number of people.
“Flow cytometry has various advantages over traditional analytical methods such as ELISA, which includes its ability to deliver precise and accurate results, It is widely used in various fields of academic, clinical research, and diagnosis of diseases such as cancer, HIV, and hematological malignancies. The rising numbers of patients suffering from all these has created an impending need for flow cytometry in the effective diagnosis as well as monitoring of diseases.”
Dr Tejal Bhatt
Consultant Pathologist, SRL Limited
The current method for COVID-19 testing, the RT-PCR, that detects viral RNA in a nasopharyngeal sample, apart from being a relatively expensive test, its sensitivity is also not considered optimal, primarily due to the delay between exposure to infection and colonization of the upper ear, nose, and throat area, from where the sample is collected. Furthermore, the RT-PCR test is adding strain on laboratories due to its significantly delayed sample processing and the delivery of results. The deep nasal swabbing for specimen collection makes the patient uncomfortable and is also potentially dangerous for the healthcare professional taking the sample.
In this context, CD169 evaluation is a promising method. The diagnostic accuracy, easy finger-prick sampling, and rapid results (15-30 minutes) of this rapid assay indicates toward its potential use.
The research team has published results among early-stage, asymptomatic patients. The CD169 flow cytometry assay demonstrated a 98 percent sensitivity in early-stage disease and a 100 percent sensitivity in asymptomatic infection. However, the assay did not demonstrate high specificity in late-stage disease, suggesting that CD169 expression decreases once the virus has cleared.
Another team from India has proposed a flow virometry process for detection of SARS-CoV-2 and large-scale screening of COVID-19 cases. Virions of severe acute respiratory syndrome coronavirus-2 could be tagged with specific fluorescent-labeled antibodies. Labeled virions could be detected using advanced flow virometry in a high-throughput manner. The proposed method could enable 2000 tests per day using a single equipment.
However, the process requires a biosafety level 3 facility and mechanization such as a robotic arm to minimize droplet infection to the workers. Samples with lower viral load may still work better for qRT-PCR-based detection, whereas for the samples with moderate to high viral load, the flow virometry method will work at an acceptable range of reliability and reproducibility.
Technology updates
Earlier this year, a novel optical microfluidic cytometry scheme for label-free detection of cells based on the self-mixing interferometry (SMI) technique was brought to light. Although, many label-free flow cytometry approaches are available, the applications remain restricted due to expensive associated costs and complex operation. Self-mixing interferometry has emerged as an ideal alternative as a result of its compact size, low-consumption and self-alignment properties.
With this novel optofluidic cytometry system, comprised of a commercial 1310 nanometer (nm) distributed feedback (DFB) laser diode, the study proposes a very simple technique for cell enumeration and classification without any extra devices such as high-speed camera, photomultiplier and spectrometer. Moreover, the fluorescence staining operation which is necessary in traditional flow cytometry methods is not also required in this system. This device aims to provide simple, fast and accurate detection of the individual cell characteristics and efficient cell type classification.
In Sept 2020, Aigenpulse announced the launch of its CytoML Experiment Suite. This is an automated, end-to-end, machine learning solution specifically aimed at streamlining and automating cytometry analysis at scale and replacing manual gating processes.
In the same month, Bio-Rad Laboratories, Inc. introduced StarBright Violet 515 (SBV515) Dye. It is the first of a new range of unique fluorescent nanoparticles that can be used in flow cytometry.
Widening increased applications
From a promising new technology to an indispensable tool, flow cytometry has evolved significantly. The wide span of its application includes development of therapies and diagnosis of various disorders, such as haematological disorders, malignancies, and various infections. Vendors are consistently introducing better equipment and software and making it more cost-effective, accurate as well as increase sensitivity and throughput. Flow cytometry techniques are increasing being connected with mass spectrometry and other molecular diagnostics instruments.
