Magnetic trapping and photoacoustic detection of rare circulating tumor cells

The presence of circulating tumor cells (CTCs) in the vasculature directly correlates with the likelihood of metastasis development. Their rarity, however, makes them difficult to detect. Recently, the potential of photoacoustic (PA) imaging for sensitive detection of nanoparticle-targeted diseased cells has been demonstrated. However, the strong blood background can easily mask the weak signal from targeted CTCs. The goal of this study is to utilize a multifunction nanoparticle composite molecularly targeted to CTCs, enabling magnetic trapping for rare cell accumulation with simultaneous PA imaging for detection. This technique greatly increases both the sensitivity and specificity of CTC detection. As an initial test, human prostate cancer cells, LNCaP, targeted with a nanocomposite combining a gold nanorod core with magnetic nanoparticles, circulated in a 1.6-mm tube at a maximum flow rate of 12 ml/min, mimicking CTCs in the human radial artery. Results show that cells can be magnetically trapped, accumulated, and detected at a concentration of only 7 cells/ml, within the typical range of CTCs in peripheral vessels for an active tumor. Future work will focus on improving the sensitivity to detect a single targeted CTC.