Biocompatible capsules deliver drugs

Researchers at the University of Illinois at Urbana-Champaign have developed an innovative strategy of mixing lipids and nanoparticles to produce new drug and agricultural materials, and delivery vehicles.

"This is a new way to make nano-size capsules of a biologically friendly material," said Steve Granick, a professor of materials science and engineering, chemistry and physics. "The hollow, deformable and biofunctional capsules could be used in drug delivery, colloidal-based biosensors and enzyme-catalysed reactions."

Lipids are the building blocks of cell membranes. The construction of useful artificial lipid vesicles was previously not possible, because the vesicles were too delicate. Granick and graduate student Liangfang Zhang found a way to stabilise lipids and stop their destruction.

To stabilise lipids, the researchers begin by preparing a dilute solution of lipid capsules of a particular size. After encapsulating chemicals in the capsules or adsorbing molecules on their surfaces, they add charged nanoparticles to the solution. The nanoparticles adhere to the capsules and prevent further growth, freezing them at the desired size. The lipid concentration can then be increased without limits.

As proof of concept, Granick and Zhang encapsulated fluorescent dyes within lipid capsules. No leakage occurred, and the lipids proved stable against further fusion.

"This opens the door to using biologically friendly capsule delivery vehicles in exciting new health and agricultural applications," Granick said. "Chemical reactions can be performed within individual isolated capsules, or on groups of capsules linked together like boxcars in a train."

The biocompatible containers could carry cargo such as enzymes, DNA, proteins and drug molecules throughout living organisms. They could also serve as surrogate factories where enzyme-catalysed reactions are performed. By attaching biomolecules to the capsule's surface, novel colloidal-size sensors could be produced. The capsules could also provide a new way of analysing drug behaviour.