Drug loading. By expanding the membranes of red blood cells and slipping drugs inside, researchers think they can deliver them more effectively.

Attack of the Red Blood Cells

Scientists are using a patient's own red blood cells to deliver needed drugs directly to cells in the body. A new test of the technique suggests that it effectively delivers steroids to the lungs of cystic fibrosis patients; furthermore, a single dose lasts for at least a month. In the long run, scientists hope the technique could also be applied to uses as diverse as gene therapy and HIV treatments.

Many therapies, such as modified genes and some novel drugs, are too cumbersome to cross cell membranes and do their job. Mauro Magnani and colleagues at the University of Urbino, Italy, wanted to overcome that problem. To do so, they immersed blood cells in a saline solution. Differences in osmotic pressure between the solution and the inside of the cells stretched out the pores in the cell membranes, allowing bulky molecules to squeeze in. When the cells were removed from the solution, they crunched back to their usual size with the drug sealed inside. A pilot study found that the cells released the steroid dexamethasone into the blood of patients with chronic obstructive pulmonary disease, and stayed in the circulating blood for 7 days.

Now, a second study shows similar success with cystic fibrosis. In the June issue of Gene Therapy, Magnani's team reports that this delivery method delivers dexamethasone, which is also used to treat this disease, to the patients' blood for 1 month. In both studies, the drug was sealed into the patients' red blood cells in an inactive form, before being broken down by the cell's enzymes to a size that can leak into the blood. Magnani believes that the technique has wide-ranging applications. Red blood cells can carry newer compounds such as modified genes and the cells can also be modified to attract specific immune cells that sometimes harbor microbes such as HIV and tuberculosis.

"It's a great strategy," says biochemist Philip Low of Purdue University in West Lafayette, Indiana. "It should certainly be able to reach the [cache] of virus that's not accessible to conventional treatment."

Related sites
Philip Low's home page
NIH pamphlet on cystic fibrosis

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