In previous studies, Anderson and Langer showed they could block multiple genes with small doses of siRNA by wrapping the RNA in fatlike molecules called lipidoids. In their latest work, the researchers set out to improve upon these particles, making them more efficient, more selective, and safer, says Yizhou Dong, a postdoc at the Koch Institute and lead author of the paper.
"We really wanted to develop materials for clinical use in the future," he says. "That's our ultimate goal for the material to achieve."
The design inspiration for the new particles came from the natural world specifically, small particles known as lipoproteins, which transport cholesterol and other fatty molecules throughout the body.
Like lipoprotein nanoparticles, the MIT team's new lipopeptide particles are spheres whose outer membranes are composed of long chains with a fatty lipid tail that faces into the particle. In the new particles, the head of the chain, which faces outward, is an amino acid (the building blocks of proteins). Strands of siRNA are carried inside the sphere, surrounded by more lipopeptide molecules. Molecules of cholesterol embedded in the membrane and an outer coating of the polymer PEG help to stabilize the structure.
The researchers tuned the particles' chemical properties, which determine their behavior, by varying the amino acids included in the particles. There are 21 amino acids found in multicellular organisms; the researchers created about 60 lipopeptide particles, each containing a different amino acid linked with one of three chemical groups an acrylate, an aldeh
|Contact: Sarah McDonnell|
Massachusetts Institute of Technology