Ultrasensitive Clinical Enumeration of Rare Cells ex Vivo Using a Micro-Hall Detector

The ability to detect rare cells (<100 cells/ml whole blood) and obtain quantitative measurements of specific biomarkers on single cells is increasingly important in basic biomedical research. Implementing such methodology for widespread use in the clinic, however, has been hampered by low cell density, small sample sizes, and requisite sample purification. To overcome these challenges, we have developed a microfluidic chip-based micro-Hall detector (mu HD), which can directly measure single, immunomagnetically tagged cells in whole blood. The mu HD can detect single cells even in the presence of vast numbers of blood cells and unbound reactants, and does not require any washing or purification steps. In addition, the high bandwidth and sensitivity of the semiconductor technology used in the mu HD enables high-throughput screening (currently similar to 10(7) cells/min). The clinical use of the mu HD chip was demonstrated by detecting circulating tumor cells in whole blood of 20 ovarian cancer patients at higher sensitivity than currently possible with clinical standards. Furthermore, the use of a panel of magnetic nanoparticles, distinguished with unique magnetization properties and bio-orthogonal chemistry, allowed simultaneous detection of the biomarkers epithelial cell adhesion molecule (EpCAM), human epidermal growth factor receptor 2 (HER2)/neu, and epidermal growth factor receptor (EGFR) on individual cells. This cost-effective, single-cell analytical technique is well suited to perform molecular and cellular diagnosis of rare cells in the clinic.