Enhanced Tumor Cell Separation by Surfaces Functionalized With Combinations of Bioadhesive Proteins

Effective detection of circulating tumor cells (CTCs) can provide important diagnostic and prognostic information of metastatic cancer. However, CTCs are extremely rare and estimated to be only in the range of one tumor cell in the background of 10⁶–10⁹ normal blood cells, hindering clinically significant detection.[1–2] The specific capturing and potential enrichment of CTCs using anti-epithelial cell adhesion molecule (anti-EpCAM)[3] and selectin, respectively, inspire a biofunctionalized surface that mimics biological complexity may detect and isolate target cells at a greater sensitivity and specificity. This concept is supported by the initial physiological interactions between CTCs and endothelium in the bloodstream, which include concurrent rolling and stationary binding steps. Towards this aim, we investigated the following: i) two proteins with distinct biofunctions (selectin to induce rolling and anti-EpCAM to statically capture target cells) can be co-immobilized; ii) a combined rolling and stationary binding can be induced by the mixture of the proteins; and iii) the biomimetic combination enhances overall capture efficiency of the surface. As a proof-of-concept study for the hypothesis of enhanced separation capacity and capture efficiency using protein mixtures, the surfaces are tested using in vitro cell lines (MCF-7 cells as a CTC model and HL-60 cells as a leukocyte model) under flow conditions. The effects of the combination of rolling (E-selectin) and stationary binding (anti-EpCAM) on capture efficiency are compared to a surface functionalized solely with anti-EpCAM.