When nanoparticles are used for drug delivery, they often end up in the liver or spleen instead of the intended target. A team led by Jacob S. Brenner and Vladimir Muzykantov of the University of Pennsylvania now shows that nanocarrier delivery can be improved by the having the nanocarriers “hitchhike” on red blood cells (Nat. Commun. 2018, DOI: 10.1038/s41467-018-05079-7). The researchers withdrew red blood cells from mice and incubated them with nanoparticles, which adsorbed on the cell surface. They then injected the cells back into the animals through arterial catheters. When injected this way, the nanocarriers accumulate in the first organ they encounter downstream from the injection site. The researchers think the narrow capillaries cause the nanoparticles to detach from the blood cells and transfer to the cells lining the capillaries. The red blood cells themselves don’t clog the arteries or capillaries. By moving the catheter to different arteries, the researchers can target different organs. Such an approach could be used to deliver drugs for acute conditions such as heart attacks and embolic strokes for which the standard of care already involves the use of arterial catheters, the researchers suggest.