Mitochondria have been used to power miniature motors for microfluidics.

Specialised subunits found within many living cells, mitochondria are essentially the cells' power plants. The structures use glucose to generate adenosine triphosphate (ATP), a multifunctional compound that transports chemical energy within cells. Now Jed Harrison from the University of Alberta, Edmonton, Canada, and colleagues have used mitochondria to synthesise ATP as fuel for molecular motors in microfluidic systems.

On-chip: kinesin moves along microtubules as ATP is hydrolysed

Roughly the size of a credit card, microfluidic devices are used to examine fluid flow in structures and channels less than a millimetre across, often being used in disease diagnostics. Using motors allows efficient fluid mixing and transport inside the devices.

ATP has already been used to power microfluidic motors based on kinesin - a protein that moves as it hydrolyses ATP. Currently, ATP is produced in microfluidics with the enzyme pyruvate kinase, but this is a low energy density fuel, and an improved ATP source is the goal.

Using mitochondria to produce ATP instead, the Canadian team found that these miniature machines could power a kinesin motor inside a two-chamber device. 'Using mitochondria directly, avoids the significant challenges associated with creating a synthetic enzyme cascade to duplicate the mitochondrial role,' explains Harrison. 'We take advantage of the biomolecular machinery nature has already assembled.'

Harrison adds that, although there are many future challenges to molecular motors, he believes this is the first step towards a system that has a high energy density fuel source and can recycle products back into ATP. 'And the simplicity of the device is a key point which should ensure its success in labs which are not specialists in microfabrication,' says Matthieu Piel, who heads a systems cell biology research group at the Curie Institute, Paris, France.

Rebecca Brodie