Researchers in Switzerland have built nanoscale cargo loading stations and shuttles, an important step towards assembly lines for nanotechnology.

Biological assembly lines consist of kinesin proteins which carry cargo, like organelles or vesicles, and literally walk along microtubules. However, as far as man-made systems go, 'nothing comparable to a macroscopic assembly line exists at the nanoscale,' according to Viola Vogel of the Department of Materials at the Swiss Federal Institute of Technology (ETH) in Zurich. 'Imagine if you wanted to build a car by fabricating all of its components, putting them in a glass full of water and hoping that they would self-assemble spontaneously into the finished car.'

The challenge is to tune the interactions in the system so that the cargo remains stuck to the station when not needed, but can be picked up easily by the shuttle. As a test of principle, Vogel and colleagues used gold nanoparticles coated in anti-biotin antibodies as cargo, and compared loading stations made of biotin-tipped DNA with biotin-tipped polyethylene glycol. Biotinylated microtubules, powered by kinesin motors, act as shuttles rather than conveyor belts, as they do in cells.

Vogel and team then tracked the fate of the gold nanoparticles with scanning electron microscopy. They found that the shuttles did indeed pick up the nanoparticles and that they held on to them, with a loss rate of about 28% over 12 minutes. They also found that DNA stations are more effective than polymer ones.

'Future challenges will be to combine the main components of a transport system: pick-up of cargo from defined locations, guided transport, and controlled discharge of the load at the final destination,' commented Vogel. She went on to caution: 'The problems are always in the details of working through the engineering challenges of interfacing biological molecules with synthetic devices.'

Colin Batchelor