Radoslav Savic and his colleagues at McGill University tested the properties of tiny units built out of two types of polymers. The two compounds self-assemble into a spherical shape known as a micelle. One compound, which is hydrophobic (water fearing), aligns facing inwards and the other, which is hydrophilic (water loving), faces outwards. Drugs can then be loaded inside the tiny molecular globs, which measure 20 to 45 nanometers in diameter. The researchers used fluorescent labeling to track the micelles' journeys (see image). They found that the tiny containers could pass through the wall of a rat cell, but did not enter the cell's nucleus. The micelles did, however, penetrate some cell parts, such as mitochondria and the Golgi apparatus, which are important targets for drug delivery.
The scientists also determined that the micelles are very efficient at delivering their hydrophobic drug cargo once inside a cell. This property could mean that doctors may one day be able to administer smaller doses of toxic medications. "These micelles may thus be worth exploring for their potential to selectively deliver drugs to specified subcellular targets," the authors note. In an accompanying commentary, Jeffrey A. Hubbell of the University of Zurich cautions that much work remains to be done, "yet, multifunctional polymer micelles have already come a long way to reaching these ends."