Tapered slit filters for high-throughput viable circulating tumor cell isolation

Abstract

This thesis presents tapered slit filters for high-throughput viable circulating tumor cell (CTC) isolation. The previous biochemical CTC isolation methods, based on surface-specific antibody bindings, showed different capture efficiencies depending on tumors with the reduced cell viability due to irreversible antibody binding. The previous physical CTC isolation methods, using straight hole filters, generated stress concentration in the captured CTC; thus resulting in cell damage and rupture. In this thesis, we propose a membrane filter having tapered slits to achieve high-throughput and viable CTC isolation with the minimal cell stress reduced to 18% of the stress generated in straight hole filters. We design two types of tapered slit filters, Filter 6 and 8, respectively containing the tapered slits hav-ing the outlet width of 6 and 8μm at the slit density of 34,445/cm2 on a membrane. We decide the outlet widths of the tapered slits considering the size and deformability of the cells in blood. We fabricate the slits having tapered angle of 2 degree on SU8 membrane by adjusting UV expose dose and the air gap between the membrane and photomask. The performance of the fabricated tapered slit filters have been characterized using the human lung cancer cells (H358G), spiked in PBS (Phosphate buffered saline) and diluted blood (blood:PBS=1:4), respec-tively. Filters 6 and 8 capture the cancer cells spiked in PBS at the efficiency of 89.87% and 80.34% at the sample flow rate of 5ml/h, respectively. Viable cells are collected from the cells captured by Filter 6 and 8 at the recovery rates of 59.14% and 72.99%, respectively; thus showing the viability of 70.24% after 5-day cell culture on the membrane filters. At the increased flow rate of 10 ml/hr, the capture efficiencies were de-creased by 20% and 62 % for Filter 6 and 8, respectively. The best cell isolation conditions of the PBS sample test is found at the flow rate of 5ml/h using Filter 6, and is used in the ...