Long-lasting liposomes

A coat of nanoparticles can prevent a popular lab-made capsule from fusing with its neighbors in solution and losing its structure, researchers report.

Liposomes are hollow, spherical capsules made from phospholipids, the same components found in cell membranes. They can be used to carry drugs or other biological cargo. But individual liposomes are fragile and tend to fuse into blobs after a couple of days, spilling their contents prematurely in the process, says Steve Granick of the University of Illinois at Urbana-Champaign. “We want to keep them discrete,” he says.

Granick and graduate student Liangfang Zhang studded the liposomes with polystyrene particles 20 nanometers (nm) in diameter. The nanoparticles covered about 25 percent of the 200-nm-diameter liposomes.

The enhanced liposomes remained stable in solution for 50 days, the researchers report in the April Nano Letters.

The method may enable researchers to make liposomes in high concentrations, in contrast to the dilute solutions used today to “prevent them from banging into each other,” says Granick. About 75 percent of an enhanced liposome’s surface is still free for attachments of biological molecules that can direct the liposome to a specific target, notes Granick.