Drug smugglers leave cellular tracks. (Chemistry).

Getting drug molecules to targets within cells is a challenge, especially when the therapeutic molecules aren't soluble or stable, or when they can be toxic to cells. To circumvent these problems, scientists are designing protective nanoscale carriers that might someday shuttle medicine to exactly where it's needed.

In the April 25 Science, Dusica Maysinger and her colleagues at McGill University in Montreal describe their new particles, or micelles, and how they behave inside rat and mouse cells.

The team made micelles from polymer molecules that have a water-attracting end and a water-avoiding end. Each polymer strand also bears a fluorescent marker. In water, the molecules spontaneously assemble into spheres just 20 to 45 nanometers wide, with their water-averse ends on the inside. Drugs that are relatively insoluble in water, including some anticancer agents, sequester themselves inside the water-averse interiors of the nanoscale micelles.

Maysinger and her colleagues applied drug-filled micelles to cells growing in lab dishes. The researchers report that the particles entered the cells and congregated in organelles such as the cell-powering mitochondria and the protein-processing Golgi apparatus. In doing so, the micelles ferried more drug molecules into each cell than would make it there on their own.

The spheres didn't penetrate the cells' nuclei. This is good, says Maysinger, since the team wanted the micelles to avoid interfering with the genetic material in the nucleus.

Maysinger says the findings are just a first step. The researchers now plan to add attachments to the micelles to make them seek out specific cellular targets where a ferried drug might prove most therapeutic.--J.G.