NanoFlares isolate metastatic breast cancer cells (MDA-MB-231) spiked into human whole blood. (A) Recovery of mCherry MDA-MB-231 cells from whole blood upon isolation with NanoFlares. (B) Relative cell-associated fluorescence of Vimentin (Vim), Fibronectin (HFN), or nontargeted Scrambled (Scr) Control NanoFlares in 100–100,000 MDA-MB-231 added to whole blood. (C) Scatter plots showing ability of Vimentin NanoFlare to detect small numbers of cells added to whole blood, with a range of 10,000, 1000, and 100 cells. ***P < 0.0005, **P < 0.005, *P < 0.05.