Trapping and photoacoustic detection of CTCs at the single cell per milliliter level with magneto-optical coupled nanoparticles.

Circulating tumor cells (CTCs) have been reported to correlate most closely with cancer development, and can serve as an important marker for metastatic malignancy, tumor recurrence, and prediction of prognosis and therapeutic effi cacy. Detecting and quantifying CTCs, however, have proven to be challenging due to their low abundance in blood. Based on magneto-optical coupled nanoprobes (made of gold nanorod and iron oxide nanoparticles) and photoacoustic (PA) imaging, we report the development of an enabling technology that can detect CTCs at single cell/mL level. Remarkably, at this low cell concentration, approximately 67% of circulating tumor cells can be captured and imaged with just one pass through the magnetic trapping zone. Compared to the conventional in vitro assays, this technology offers signifi cantly improved sensitivity, because it is inherently compatible with large sample volumes. Compared to more advanced in vivo CTC detection methods, this technology can solve the low throughput problem of optical imaging, and streamline the photoacoustic imaging process by combining magnetic enrichment and digital readout into a single step. Most cancer deaths are caused by metastasis, a process