Figure 1. Isolating CTCs. The circulating tumor cell (CTC)-iChip uses magnetic beads to label cells in whole blood. The blood sample is loaded onto the chip, on which lateral displacement, inertial focusing and magnetophoresis separate and collect the cells of interest from the bulk.

(I) Positive selection incorporates epithelial cell adhesion molecule (EpCAM)-targeting magnetic beads to bind CTCs, and (II) negative depletion incorporates common leukocyte antigen CD45-binding and granulocyte marker CD15 (fucosyltransferase 4 a1,3 fucosyltransferase myeloid-specific; FUT4; SSEA-1)-targeting magnetic beads to bind white blood cells (WBCs).

During lateral displacement, the sample moves through an array of microposts, spaced 32 mm apart, which results in size-based separation and retention of nucleated cells. Red blood cells (RBCs), platelets and other components exit the device.

For inertial focusing, the nucleated cells enter an asymmetrical, curved channel and exit as a tight row of individual cells.

Finally, with magnetophoresis, a magnetic field (ÑB) separates magnetically labeled cells from unlabeled cells and provides an isolated supply of CTCs in solution.

In total, the device can process about 8 mL of whole blood per hour, translating to about 107 total cells per second. (Figure based on Figure 1a in ref. 1.)