No abstract

Capture of circulating tumor cells (CTCs) from peripheral blood of cancer patients has major implications for metastatic detection and therapy analyses. Here we demonstrated a microfluidic device for high efficiency and high purity capture of CTCs. The key novelty of this approach lies on the integration of a microfilter with conical-shaped holes and a micro-injector with cross-flow components for size dependent capture of tumor cells without significant retention of non-tumor cells. Under conditions of constant flow rate, tumor cells spiked into phosphate buffered saline could be recovered and then cultured for further analyses. When tumor cells were spiked in blood of healthy donors, they could also be recovered at high efficiency and high clearance efficiency of white blood cells. When the same device was used for clinical validation, CTCs could be detected in blood samples of cancer patients but not in that of healthy donors. Finally, the capture efficiency of tumor cells is cell-type dependent but the hole size of the filter should be more closely correlated to the nuclei size of the tumor cells. Together with the advantage of easy operation, low-cost and high potential of integration, this approach offers unprecedented opportunities for metastatic detection and cancer treatment monitoring.C irculating tumor cells (CTCs) in peripheral blood of cancer patients are reliable biomarkers for metastatic detection and treatment monitoring. The challenge is to capture them with a high efficiency and high purity, despite their extreme rarity and high phenotype heterogeneity [1][2][3][4][5][6][7][8][9][10] . Currently, two approaches are in competition, depending on whether or not the capture is affinity-based. The affinity-based capture relies on immunochemical interaction between magnetic beads [11][12][13][14][15][16] or patterned structures [17][18][19][20] and tumor cells that express special surface markers such as EpCAM, an epithelial cell adhesion molecule over expressed by majority of tumor cells. These methods are efficient for capturing CTCs of epithelial phenotypes but not applicable to those with down-regulated or lost epithelial markers. Indeed, it is known that tumor cells of epithelial origin may undergo epithelial to mesenchymal transition 21,22 . In contrast, the non-affinity methods, including centrifuging deflection [23][24][25][26][27] , dielectrophoretic separation [28][29][30] and size-based filtration 12,[31][32][33][34][35][36][37][38][39][40][41][42][43][44] , are able to isolate both epithelial and mesenchymal phenotypes, which are more appropriate for analyses of tumor heterogeneity, tumor drug resistance, etc. However, these approaches are technologically biased and it is often difficult to reach a trade-off between capture efficiency, purity and cell viability which are all important criteria for both fundamental and clinical studies. For example, the size-based filtration has been developed for more than several decades but the most of reported results were obtained by using track-etche...