A tiny machine capable of travelling under its own steam has been engineered by Japanese researchers. The fuel used to propel the vehicle - adenosine triphosphate (ATP), the universal power behind cellular activity - is generated on board.

Masato Kodaka and colleagues of the National Institute of Advanced Industrial Science and Technology were fascinated by nature's own tiny locomotives: motion-producing proteins called kinesins that transport biochemical essentials along networks of tiny string-like microtubules in cells.

Kodaka's team were inspired by the movement of a single microtubule along a glass surface coated with kinesin. They have also developed a new polymer particle that would easily couple to the microtubules, and is ideal for connecting additional chemical components. Attaching an ATP-producing enzyme to the coupled bead-microtubule hybrid results in a working nano-biomachine bearing its own cargo of fuel. Possible applications of the hybrid nano-biomachine include transporting or sensing chemicals.

Henry Hess, a researcher in molecular bioengineering and nanotechnology at the University of Washington, US, agreed that the work is 'an exciting step towards the assembly of integrated, multi-functional bionanodevices. Maybe inspired by diesel-electric locomotives, their device incorporates for the first time the on-board generation of ATP for its motor protein engines from energy-rich precursors'.

The authors imagine that their functional polymer bead allows their machine to be easily adapted to transport any chemical or biological molecules. As immobilising molecules onto microtubules is difficult to achieve in the lab, this takes research one step further toward mimicking nature's railroads.

Sula Armstrong