Abstract 4070: Development of circulating tumor cell capture from whole blood using beads and microfluidics
Authors: Kralj Jason G. , Arya Chanda , Forbes Thomas P. , Munson Matthew S. , Forry Samuel P. 
Published: August 2012

Abstract
Capture of circulating tumor cells (CTCs) from blood shows promise as a relatively non-invasive screen for early stage metastasis, treatment efficacy, and disease progression. Capture rates exceeding 80% of CTCs from whole blood have been demonstrated in microfluidic chips, with good specificity and throughput at approximately 1 mL/h. The most common approach is to design a high surface-area microdevice and functionalize the surface with anti-EpCAM to capture epithelial tumor cells. As an alternative to this monolithic design, we have developed a CTC capture strategy based on functionalized beads for analyzing small numbers of CTCs from whole blood. Beads for the device were commercially available in a variety of sizes and surface chemistries or could be synthesized by multiple techniques. We utilized avidin-functionalized beads to enable capture using biotinylated antibodies (Ab) for surface-expressed proteins. Critically, batches of beads were assayed in bulk and then used for multiple experiments, avoiding characterization of each device. Beads packed well as columns in microdevices, ensuring multiple surface interactions as cells flow through. We simulated CTC-carrying blood by spiking human breast cancer adenocarcinoma (MFC7) cells (prestained with a membrane dye) into whole human blood between 1000 cells/mL and 105 cells/mL. Samples were delivered through the packed bed of beads using a syringe pump. We found that adding Ab to whole blood samples provided superior results to pre-coating the beads with the Ab. This approach was tested for multiple bead compositions and enabled (1) use of less Ab, and (2) higher capture rates, perhaps due to the rapid biotin:avidin binding. Significant cell capture was observed when as few as 300 cells were introduced into the device. At all cell densities, the majority of captured cells bound to the first few rows of beads, with decreasing capture frequency along the length of the column. Quantification of the absolute number of captured cells was a challenge in whole blood samples due to the large numbers of cells captured and optical distortion effects. We estimated capture by observing the initial capture rates of the same cells at the same densities in serum-spiked phosphate-buffered saline. This indicated that during the initial stages of flow, over 80% of the Ab-labeled cells were selectively captured. We conclude that the device can handle higher flowrates and still capture the majority of labeled cells. We are exploring the feasibility of this approach for capturing even lower CTC concentrations (1 cell/ml to 100 cells/mL range). Our bead/microfluidic approach simplifies CTC capture by enabling bulk surface functionalization for multiple experiments and allowing commercial sourcing of all functional elements. Further, there is flexibility in antibody selection, such that alternate Ab could rapidly be considered.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4070. doi:1538-7445.AM2012-4070