Red blood cells may one day do more than carry oxygen around the body – they have been genetically engineered to act as miniature drug delivery vehicles.
Many drugs only last for hours in the bloodstream before being broken down by the liver. Since red blood cells live for several months, a team at the Whitehead Institute for Biomedical Research in Massachusetts wondered if engineering them to carry drugs may offer a longer-lasting alternative.
To find out, the researchers took bone marrow from mice and isolated the cellular precursors to red blood cells. They inserted a gene for a protein called Kell that sits on the cell surface.
Kell acts like a handle, says team member Hidde Ploegh. Molecules can be attached to it by bathing the precursor cells with enzymes and the desired molecules.
The team was able to attach an easy-to-track molecule called biotin. When the altered cells were injected into mice, they survived almost as long as normal.
In future tests, drugs or antibodies could be attached instead. "You can pretty much attach anything you wish," says Ploegh.
It should also be possible to send drugs to different parts of the body by attaching antibodies that recognise molecules on specific tissues as well as the medicine, he says.
What's more, concerns about genetic engineering should not apply to the red blood cells, since they expel their DNA when mature.
Other ways of getting red blood cells to carry medicines are being investigated, including putting drugs inside them, but this approach tends to weaken the cells and reduces their lifespan.
Journal reference: PNAS, DOI: 10.1073/pnas.1409861111