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UBC Theses and Dissertations

Separation of circulating tumor cells using resettable cell traps Qin, Xi


Immunoenrichment of conventional circulating tumor cells (CTCs) may fail to capture cells with poor antigen expression. Micropore filtration is a compelling label-free alternative to separate CTCs based on their biophysical characteristics rather than biochemical characteristics. However, this strategy is prone to clogging of the filter microstructure, which dramatically reduces selectivity after processing large numbers of cells. Our group previously reported the resettable cell trap (RCT) mechanism to perform micropore filtration in a way that is resistant to clogging. We improved the selectivity of this label-free mechanism by filtering the samples multiple times on chip and dramatically improving the throughput by parallelization. The resettable cell trap device is a microfluidic mechanical constriction with adjustable apertures that can capture CTCs based on their distinct size and deformability. It can also be periodically cleared to release the trapped cells to prevent clogging. Three identical cell traps are aligned in series which improves selectivity by removing leukocytes that non-specifically adhere to the surface of microchannels. We validated this mechanism by doping UM-UC13 bladder cancer cells into diluted whole blood at a density of 1 UC13 to 1000 leukocytes. The first filtration step achieved 183-fold enrichment and 93.8% yield. The second and third traps together provided an additional enrichment of ~5 without significant change in yield. Furthermore, additional filtration steps provide even greater enrichment. In patients with metastatic castration-resistant prostate cancer (mCRPC, n=24) and localized prostate cancer (LPC, n=18), CTCs were successfully identified using the resettable cell trap device followed by single-cell spectral analysis. We additionally compared the RCT device to the CellSearch® System, the only FDA approved commercial CTC enumeration platform. The microfluidic RCT device identified 83.3% (20/24) patients with >=5 CTCs per 7.5 ml of blood with a mean of 329 counts. Within the same patient group, the CellSearch only measured >=5 CTCs in 37.5% (9/24) patients with a mean of 23 CTCs per 7.5 ml of blood. The RCT device identified significant more CTCs and positively identified more mCRPC patients than the CellSearch system.

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