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Posted: Mar 06, 2006
Nanoparticles create biocompatible capsules
(Nanowerk News) An innovative strategy of mixing lipids and nanoparticles to produce new drug and agricultural materials and delivery vehicles has been developed by researchers at the University of Illinois at Urbana-Champaign (see also our earlier article about this research, titled Nanoparticle-stabilized liposomes in the Feb 28, 2006 edition of Nanowerk Spotlight).
“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-catalyzed 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 stabilize lipids and stop their destruction. The
researchers describe their technique in a paper accepted for publication
in the journal Nano Letters, and posted on its Web site.
To stabilize 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-catalyzed reactions are
performed. By attaching biomolecules to the capsule’s surface,
novel colloidal-size sensors could be produced.
An additional use for stabilized lipid capsules is the study of drug
behavior. “A drug contained in this nano environment is like a
fish swimming inside a bowl,” Granick said. “We can study
the ‘fish’ in detail, and it won’t swim away.”