On the right track

Towards a true lab-on-a-chip system.

Rail enthusiasts might be interested in research going on in the US looking at understanding and controlling how objects move in small devices. Whilst most current work has been limited to looking at how microtubules move along single tracks this study looks at three new types of junction - a crossing junction (allows crossing at right or shallow angles), a reflector junction (allows flow in a single direction) and a circular concentrator (to collect microtubules) - to create extensive networks of track to sort and control movement of microtubule shuttles for applications such as molecular scale self-assembly. In the words of one independent researcher, ’where the previous work reports the invention of the steam train, this reports the founding of a railway’.

Viola Vogel and colleagues from the University of Washington and Sandia National Laboratories, Albuquerque, have looked at ways to incorporate the motor protein kinesin into synthetic devices to allow microtubules to be actively transported. In active transport systems, material can be moved 10 times faster than by diffusion alone, and by making use of a biological motor protein, all the ground work of designing this kind of miniature machine has already been done by Nature. The kinesin is coated onto flexible tracks with adenosine 5’-triphosphate (ATP) as the power source and fluorescent microtubules are used to allow movement to be monitored with a fluorescence microscope. Commenting on the work, Yoshinobu Baba, director of the Nanodevice Project at the University of Tokushima, Japan, said that ’kinesin might provide the option for a source of transport power in microfluidic devices in addition to previous pressure-driven or [by] electroosmotic flow’. He added that this work shows ’a new approach from the biological perspective to the next generation of lab-on-a-chip transport systems’.

In Vogel’s opinion ’the miniaturisation of microfluidic devices to the nanoscale is not possible with current technologies due to the high drag forces experienced by a fluid that is pumped through nanochannels.’ Her goal for the future is ’to explore how to best take advantage of biological nanosystems for the advancement of technology, particularly in areas where the application of conventional methods has reached it limits’. The field of bionanotechnology fascinates Vogel: ’It merges modern biology with physical sciences and engineering to address major challenges that society is facing, for example the explosion of health care costs’. In short, bringing us closer to a true lab-on-a-chip system.

Steven Evans