Capillary-Driven Microfluidic Devices for Sample Preparation of Bio-Medical Specimens
Abstract: Sample preparation is an integral part of bio-medical analysis routines, as it makes specimens of interest compatible with downstream instrumentation. Correct and proper sample preparation is of critical importance for reliable analysis results. However, conventional preparation procedures often entail numerous manual user interactions, which cause variations in sample quality and can lead to biased results. Microfluidics is a promising technology to address these problems since on-chip integration of sample preparation steps, such as volume metering, liquid handling, and sample fixation, can minimize critical user interactions. This thesis explores capillary-driven microfluidic devices for sample preparation of bio-medical specimens in patient-centric blood analysis workflows and laboratory environments. Patient-centric blood analysis, where patients take and send samples to a central laboratory for quality-assured readout, is an emerging field where capillary-driven microfluidic solutions can enable consistent sample preparation in remote locations. Blood plasma, the gold standard in blood analysis routines, is typically extracted by centrifugation, which is not readily available in remote settings. To address this limitation, we realized a microfluidic device for capillary-driven blood plasma separation from undiluted human whole blood. Based on this approach, we developed a device that generates a volume-defined dried plasma spot ready to be shipped to a laboratory for mass spectrometry. Using the same plasma separation approach, we developed a device that performs the critical analyte binding step of a multiplexed immunoassay at the time of sample collection. Sample drying and shipment to a laboratory then allow to make use of the unparalleled performance of highly specialized laboratory equipment. Along the same line of patientcentric workflows, we showed that specially treated dry blood samples enablered and white blood cell quantification with good correlation to gold standard hematology analyzer data. In addition, this thesis describes microfluidic devices that prepare samples in laboratory environments. We present microfluidic alternatives to manual procedures for the preparation of virus particles and proteins for transmission electron microscopy, and for the preparation of liquid biopsy samples for cytology investigations.
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