Trapping and dynamic manipulation of magnetic contrast agent targeted cancer cells in photoacoustic imaging: Phantom study

Magnetomotive photoacoustic imaging has been extended to address the problem of trapping and manipulating large micro-scale objects, mimicking circulating tumor cells, within a flow stream. Coupled contrast agents combining magneto-sensitive nanospheres and gold nanorods were targeted to 10 μm diameter polystyrene beads using amino acid conjugates to mimic targeting metastatic cancer cells circulating in blood. A dual magnet system was designed and built to produce external magnetic fields consisting of a polarizing field to magnetize the magnetic contrast agents, and a high gradient magnetic field producing a strong trapping force to the magnetized contrast agents. The results demonstrate that targeted polystyrene beads can be successfully trapped in a recirculating system with flow rate of 12 ml/min. In addition to magnetic trapping, the manipulation of accumulated beads has been demonstrated to suppress undesirable background signals for sensitive and specific detection of targeted objects.