Nanotech News

November 21, 2005

Virus-Mimicking Nanocages for Selective Drug Delivery

Taking a cue from nature, a team of investigators at Washington University in St. Louis has created synthetic molecular cages that, like viruses, can trap drug molecules within their interiors. These nanocages could thus serve as a versatile drug delivery vehicle capable of being targeted to tumors.

Karen Wooley, Ph.D., and her colleagues used a method that enables them to construct a molecular cage surrounding a polymer core. Once the cage is complete, the core is removed using ozone, which does not degrade the cage. The cage is designed to have reactive chemical groups on its surface, which can be used to attach both drug and tumor targeting molecules. The researchers also developed methods for constructing cages in which additional reactive groups line the interior of the cages. The investigators note that having these reactive groups on both the inside and outside of the cage creates an opportunity to design nanoscale drug delivery agents that can release its cargo upon receiving molecular signals specific to diseased tissue, such as tumor cells. This work appears in the Journal of Controlled Release.

The researchers were also able to create cages that have hydrophobic, or water-avoiding, chemical groups lining the cage interior. The presence of these groups makes it possible for the cages to carry hydrophobic drug molecules — many anticancer drugs are hydrophobic and are often difficult to administer to patients because they are not easily dissolved in water. These hydrophobic nanocages, however, were good at taking up drugs that are insoluble or slightly soluble in water, such as the anticancer agent methotrexate. Nanocages with a hydrophobic interior were capable of carrying over 400 methotrexate molecules per nanoparticle. In contrast, nanocages with a hydrophilic interior — one that is hospitable to water — could carry less than 30 methotrexate molecules per particle.

This work, which was funded in part by the National Cancer Institute and the National Institutes of Health, is detailed in a paper titled, "Regiochemical functionalization of a nanoscale cage-like structure: robust core-shell nanostructures crafted as vessels for selective uptake and release of small and large guests." This work was published online in advance of print publication. An abstract is available through PubMed.
View abstract.