In the study, Farokhzad, Langer and colleagues tailor-made tiny sponge-like nanoparticles laced with the drug docetaxel. The particles are specifically designed to dissolve in a cell's internal fluids, releasing the anti-cancer drug either rapidly or slowly, depending on what is needed. These nanoparticles were purposely made from materials that are familiar and approved for medical applications by the U.S. Food and Drug Administration. Thus all of the ingredients are known to be safe.
Also, to make sure only the correct cells are hit, the nanoparticles are "decorated" on the outside with targeting molecules called aptamers, tiny chunks of genetic material. Like homing devices, the aptamers specifically recognize the surface molecules on cancer cells, while avoiding normal cells. In other words, the bus is driven to the correct depot.
In addition, the nanoparticles also display polyethylene glycol molecules, which keep them from being rapidly destroyed by macrophages, cells that guard against foreign substances entering the body.
The team chose nanoparticles as drug-delivery vehicles because they are so small that living cells readily swallow them when they arrive at the cell's surface. Langer said that particles larger than 200 nanometers are less likely to get through a cell's membrane. A nanometer is one-billionth of a meter.
The Farokhzad-Langer team created particles that are about 150 nanometers in size: a thousand sitting side by side might equal the width of a human hair.