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UBC Theses and Dissertations

Characterization of filter membranes with application to red blood cell removal Wu, Zhongnan


Removing red blood cells (RBCs) from blood to general RBC poor plasma is a common practice during blood tests, which improves the accuracy of biomarker detection in plasma. Membrane filtration is a promising technique that utilizes a filter membrane to retain undesired blood cells while letting plasma pass through. Compared to the conventional method of centrifugation, membrane filtration features high portability and low cost due to the simple mechanism it is based on. As the most critical component in membrane filtration, filter membrane can significantly affect the quality of the generated plasma and the efficiency of the overall process. In this thesis, we conduct filtration with four commercial membranes with different properties and compare the performance parameters relevant in RBC filtration. We firstly characterize the permeability of the four membranes by passing water through them, investigating the membranes’ flow-induced permeability change. Microspheres with a mean diameter of 2.9 µm are then used to mimic the effective filtration size of human RBCs to investigate and compare the performance of the membranes for filtration. We notice that the filtration efficiency depends on the volume of fluid to be filtered and the operational condition of filtration. To test the membrane’s suitability for blood filtration, the four membranes are tested with human blood or its components. Coagulation factors are our target biomarker to be analyzed in the generated plasma. The biomarker depletion on the membranes is measured by passing plasma through the membranes. RBC lysis and leakage under different driving pressures are also evaluated by conducting filtration of RBC-plasma mixture and diluted human whole blood. With a filtration pressure up to 9 kPa, the tested polycarbonate (PC) membrane with track-etched pores shows the most promising filtrate quality with low hemolysis and leakage ratio. The tested polysulfone (PS) membrane with a gradient structure, on the other hand, can preserve more biomarkers in the fluid. The selection of the membrane should also consider other factors such as the biomarker detection method utilized.

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