Study of Circulating Tumor Cells using Microfluidic Technology: From Isolation to Analysis

Abstract

An intimidating aspect of cancer is its ability to spread out to distant organs causing 90% of cancer-associated deaths. This metastatic progression is driven by circulating tumor cells (CTCs) shed from the primary tumor into bloodstream of carcinoma patients. As a result, CTCs hold great promise as a potential biomarker in areas of cancer diagnosis, monitoring, and evaluation of therapeutic efficacy for personalized medicine, which can serve as surrogate for invasive tissue biopsy. However, theses cells are extremely rare with a frequency of only 1-10 cells surrounded by billions of normal blood cells in 1mL of blood. This thesis delineates the shortcomings of existing CTC isolation methods followed by development and implementation of new microfluidic-based platforms to improve the sensitivity, specificity, and throughput for CTC enrichment. First, an affinity-based CTC isolation chip is introduced incorporating functional graphene oxide for high-density tumor specific antibody presentation. The two-dimensional surface-capture approach shows an overall CTC capture efficiency of >82.3% for flow rates up to 3mL/hr, while maintaining high viability (>90%) from low shear stress generated during sample processing. The extremely low blood cell contamination rate in the order of 100 cells/mL enables subsequent downstream analysis of CTCs. The clinical validity of the chip is demonstrated in a cohort of 47 metastatic breast cancer patients. Second, a size based CTC isolation chip is presented utilizing the inertial force effects to isolate CTCs by differentially focusing. Channel design parameters including the height, width, and radius of curvature and flow conditions are investigated to observe their effect on particle/cell focusing and streak migration. Optimal flow regimes to achieve maximum separation of 10/20 μm particles, representing leukocytes and CTCs respectively, in various channel configurations are identified. Based on these results, a cascaded spiral chip is designed for label-free CTC isolation achieving 87.76% recovery rate with 97.91% leukocyte depletion. Finally, a catheter based in-vivo CTC isolation system is implemented for large blood volume CTC screening. The system includes a dual lumen catheter to connect the patient blood veins, a peristaltic pump for continuous blood sampling, heparin injector to prevent blood clogging and clotting, and a CTC capture module.