Design and fabrication of a portable, point-of-care, microfluidic cytometer for whole blood analysis

Meggie Marla Gene Grafton, Purdue University

Abstract

Flow cytometry is a standard technique used for cell sorting and analysis. The technology has been in existence for the past 40 years and has been developed to near perfection. However, flow cytometers are large, expensive, and required trained personnel to run the equipment and analyze the data. Due to a number of recent technological advances, a hand-held flow cytometer can be achieved by microfluidic and nanophotonic devices. Often microfluidics-based analyzers, while miniature in themselves, require cumbersome bench-top “readers” to obtain data from them. It is now possible to reduce reader size by the use of semiconductor illuminators, optical sensors (all battery powered) and sensitive cell markers such as immuno-quantum dot (Qdot) labels. The specific application described is of a portable blood analyzer that can quickly process a drop of whole, unfractionated human peripheral blood by real-time, on-chip magnetic separation of white blood cells (WBCs) and red blood cells (RBCs) and further fluorescence analysis of Qdot labeled WBC subsets. The portable cytometer was designed according to requirements set forth by NASA and requirements driven by the need for portability. Factors include small size, light weight, battery-power, accuracy, reliability and robustness. The cytometer chip was made from PDMS and fluid was driven with a syringe drive (for prototyping only.) Peripheral blood leukocytes were labeled with immuno-magnetic beads, Hoechst 33342 dye and immuno-Qdots for microscopic characterization. An LED excitation-avalanche photodiode detection system (Sensl Technologies, Ltd., Cork Ireland) was used for immuno-Qdot detection of WBC subsets. Flow of single cells was visualized and recorded by video microscopy to confirm cell paths in various microfluidic chip designs and under different labeling and flow conditions. A permanent magnet was used on-chip for diverting labeled cells. Preliminary data acquisition algorithms were also designed and tested. Ultimately great progress was made in developing a portable cytometer. PDMS chips were designed and tested with labeled blood cells, a magnetic sorting system was implemented on-chip, an optical detection system was configured with sufficient sensitivity, and data acquisition algorithms were tested. Overall the system is on track to be portable, light weight, robust, and reliable.

Degree

Ph.D.

Advisors

Leary, Purdue University.

Subject Area

Biomedical engineering

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