Abstract B24: Integration of filtration with immunoaffinity for isolating circulating tumor cells from pancreatic and colorectal cancer patients
Authors: Fan Hugh , Chen Kangfu , Dopico Pablo , Amontree Jacob , George Thomas 
Published: June 2020

Abstract
We report two microfluidic devices that combine filtration and immunoaffinity for the detection of circulating tumor cells (CTCs) from peripheral blood samples of pancreatic and colorectal cancer patients. Our approach contrasts with most CTC isolation methods that are based either on cells’ physical property (e.g., size-based filtration) or on biologic property (e.g., immunoaffinity). The combined approach addresses the challenges related to CTCs’ heterogeneity in their properties. For instance, immunoaffinity-based methods such as CellSearch® that employ antibodies against epithelial cell adhesion molecule (EpCAM) cannot isolate those CTCs expressing little or no EpCAM. Filtration-based methods cannot detect CTCs of a size smaller than the predefined filter pore diameter while many normal blood cells of a size larger than the pore are retained by the filter. Our microfluidic devices contain a serpentine main channel and an array of lateral microfilters. The key difference of our devices from the conventional filtration platforms is that our filters are not in the direction of the main flow. The unique design of the device layout leads to a two-dimensional flow that allows the majority of a sample to pass by while all cells have opportunities to interact with filters, resulting in a larger throughput, reduced cell clogging, and increased purity of cells isolated. Another advantage of our devices is that a series of filter sizes can be created in one device to accommodate different CTC diameters, which is difficult to achieve in traditional filtration platforms. Our devices are further functionalized by immobilizing antibodies on the surfaces of microfilters to combine filtration with immunoaffinity for CTC isolation. We have designed one device with filter sizes of 6-10 μm and another device with filter sizes of 12-24 μm, and we tested them for the isolation of L3.6pl cells (pancreatic cancer cells) spiked in a buffer or blood. We compared an antibody-immobilized device with the same device containing filters only. Without antibody, the device has a capture efficiency from 69.8% to 83.9%, depending on the flow rate used. With antibody, the device with combined CTC isolation mechanisms can accomplish a capture efficiency of (98.7 ± 1.2)% at a flow rate of 1.8 mL/h. Other tumor cells with different sizes have also been evaluated in the devices. Further, we employed the devices for enumerating CTCs from blood samples of pancreatic and colorectal cancer patients. We compared our integration devices with a previously reported device containing herringbone-based micromixers. We found that the integration devices generally detected a higher number of CTCs. In summary, microfluidic devices have been developed to integrate filtration with immunoaffinity for CTC isolation. The devices offer better performance than those based on one isolation mechanism only, with a potential to address CTC heterogeneity and detect CTCs with different sizes and various expression levels.
Citation Format: Hugh Fan, Kangfu Chen, Pablo Dopico, Jacob Amontree, Thomas George. Integration of filtration with immunoaffinity for isolating circulating tumor cells from pancreatic and colorectal cancer patients [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr B24.