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A cartridge-based, disposable magnetophoretic cytometer testing 3-part leukocyte differentials for point-of-care or self-testing applications. 

Membrane antigens are phenotypic signatures of cells used for distinguishing various subpopulations and, therefore, are of great interest for diagnosis of diseases and monitoring of patients in hematology and oncology. Existing methods to measure antigen expression of a target subpopulation in blood samples require labor-intensive lysis of contaminating cells and subsequent analysis with complex and bulky instruments in specialized laboratories. To address this long-standing limitation in clinical cytometry, we introduce a microchip-based technique that can directly measure surface expression of target cells in hematological samples. Our microchip isolates an immunomagnetically-labeled target cell population from the contaminating background in whole blood and then utilizes the differential responses of target cells to on-chip magnetic manipulation to estimate their antigen expression. Moreover, manipulating cells with chip-sized permanent magnets and performing quantitative measurements via an on-chip electrical sensor network allows the assay to be performed in a portable platform with no reliance on laboratory infrastructure. Using our technique, we could successfully measure expressions of the CD45 antigen that is commonly expressed by white blood cells, as well as CD34 that is expressed by scarce hematopoietic progenitor cells, which constitutes only ∼0.0001% of all blood cells, directly from whole blood. With our technology, flow cytometry can potentially become a rapid bedside or at-home testing method that is available around the clock in environments where this invaluable assay with proven clinical utility is currently either outsourced or not even accessible. 

Due to the vast difference in surface expression levels among cell populations, flow cytometers must possess a dynamic range sufficiently high to accommodate such variations. We recently introduced a microchip-based flow cytometer that combines magnetophoresis and distributed Coulter sensing. Inspired from digital photography techniques, we implemented exposure bracketing in magnetophoretic cell sorting to enhance the dynamic range of cell surface expression measurements with our electronic cytometry chip. 

Identification of membrane antigens and measurement of their expression within a cell population is of fundamental importance to medical and biological studies. In this work, we present a cytometry approach that is based on magnetophoresis and distributed Coulter sensing in a microfluidic system. Our magnetophoretic cytometer offers quantitative analysis of cell membrane antigens on a portable and disposable platform compared to conventional flow cytometers, which are complex, expensive and large systems. Our tests with human breast cancer cells show the utility of our microfluidic device and its potential as a point-of-care instrument for biomedical testing. 

Membrane antigens control cell function by regulating biochemical interactions and hence are routinely used as diagnostic and prognostic targets in biomedicine. Fluorescent labeling and subsequent optical interrogation of cell membrane antigens, while highly effective, limit expression profiling to centralized facilities that can afford and operate complex instrumentation. Here, we introduce a cytometry technique that computes surface expression of immunomagnetically labeled cells by electrically tracking their trajectory under a magnetic field gradient on a microfluidic chip with a throughput of >500 cells per min. In addition to enabling the creation of a frugal cytometry platform, this immunomagnetic cell manipulation-based measurement approach allows direct expression profiling of target subpopulations from non-purified samples. We applied our technology to measure epithelial cell adhesion molecule expression on human breast cancer cells. Once calibrated, surface expression and size measurements match remarkably well with fluorescence-based measurements from a commercial flow cytometer. Quantitative measurements of biochemical and biophysical cell characteristics with a disposable cytometer have the potential to impact point of care testing of clinical samples particularly in resource limited settings.