Nanoparticles are seemingly a great way to treat tumors, but they’re so rapidly washed out by the bloodstream that few of the nanoparticles actually reach their targets. Researchers at Drexel University have now developed a surface treatment that gives nanoparticles a significant advantage to overcome the body’s filtration system and therefore make nanotherapies much more effective.

The researchers developed hairy polymer shells within which nanoparticles can be encapsulated, and which the immune system ignores, while the liver lets the shells circulate back into the bloodstream.

Plasma proteins are a primary way for the body to tag which objects the immune system should get rid of, and macrophages then act to remove them. Turns out that sinusoidal endothelial cells of the liver are also responsible for removing tagged objects, a recent finding of the Drexel research team.

They also showed that a coating of polyethylene glycol hairs keeps the plasma proteins away, not letting them tag the nanoparticles. Additionally, having sections that are even denser than the hair-like surface prevents the liver from filtering them out, and using both techniques on the same nanoparticles lets them remain in the bloodstream for a long time.