Targeting of perfluorocarbon microbubbles to selective populations of circulating blood cells

Perfluorocarbon microbubbles (MBs) are routinely used as in vivo ultrasound contrast reagent. In addition, there is great interest in the use of MBs for ultrasound-mediated delivery, for example, of drugs and genes. As MB size (1-10 microm) limits their distribution to the vasculature, we aimed to assess the efficiency of targeting MBs to circulating cells using antibodies. Our experiments showed that MBs efficiently bind to erythrocytes and B-lymphoma cells in blood. The maximum binding was reached at a cell/MB ratio of 1:1. Following binding, the cells acquired buoyancy that allowed their easy separation from blood with brief centrifugation. Coating the MBs with DNA did not interfere with binding to cells. Experiments in mice showed that intravenously injected targeted MBs efficiently chased and bound to preinjected target cells in the bloodstream. Our data demonstrate the potential in targeting of blood cells for diagnostics and therapy.