Abstract
Miniaturizing flow cytometry requires a comprehensive approach to redesigning the conventional fluidic and optical systems to have a small footprint and simple usage and to enable rapid cell analysis. Microfluidic methods have addressed some challenges in limiting the realization of microflow cytometry, but most microfluidics-based flow cytometry techniques still rely on bulky equipment (e.g., high-precision syringe pumps and bench-top microscopes). Here, we describe a comprehensive approach that achieves high-throughput white blood cell (WBC) counting in a portable and handheld manner, thereby allowing the complete miniaturization of flow cytometry. Our approach integrates three major components: a motorized smart pipette for accurate volume metering and controllable liquid pumping, a microfluidic cell concentrator for target cell enrichment, and a miniaturized fluorescence microscope for portable flow cytometric analysis. We first validated the capability of each component by precisely metering various fluid samples and controlling flow rates in a range from 219.5 to 840.5 μL/min, achieving high sample-volume reduction via on-chip WBC enrichment, and successfully counting single WBCs flowing through a region of interrogation. We synergistically combined the three major components to create a handheld, integrated microflow cytometer and operated it with a simple protocol of drawing up a blood sample via pipetting and injecting the sample into the microfluidic concentrator by powering the motorized smart pipette. We then demonstrated the utility of the microflow cytometer as a quality control means for leukoreduced blood products, quantitatively analyzing residual WBCs (rWBCs) in blood samples present at concentrations as low as 0.1 rWBCs/μL. These portable, controllable, high-throughput, and quantitative microflow cytometric technologies provide promising ways of miniaturizing flow cytometry.
Highlights
Flow cytometry is a high-throughput cell phenotyping technology in which a large population of single cells in suspension can be examined as they pass through a region of interrogation (ROI) [1,2,3]
We demonstrated the capability of the integrated approach for a microflow cytometric application, residual WBCs (rWBCs) counting, by operating the microfluidic concentrator using the smart pipette and simultaneously counting rWBCs using the miniaturized microscope
We showed the same application using the same microfluidic device used in our previous work [18], the synergetic integration of the major components for microflow cytometry to enable handheld operation is a new approach not previously reported
Summary
Flow cytometry is a high-throughput cell phenotyping technology in which a large population of single cells in suspension can be examined as they pass through a region of interrogation (ROI) [1,2,3]. Optical technologies have demonstrated the potential of microflow cytometry for mobile healthcare by incorporating a smartphone into a flow cytometer to use its integrated imaging sensor and its computing and communication capabilities [16], and researchers have utilized simplified, lens-free optical systems based on holographic imaging for flow cytometric analysis [17]. We demonstrated the capability of the integrated approach for a microflow cytometric application, rWBC counting, by operating the microfluidic concentrator using the smart pipette and simultaneously counting rWBCs using the miniaturized microscope. Using the integrated microflow cytometer, we successfully measured low concentrations of rWBCs as low as 0.1 rWBCs/μL at a high throughput of about 370.4 μL/min, successfully demonstrating its potential for handheld flow cytometric applications
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