30 August 2005: Molecular interactions revealed in a drop of water
Femtolitre-sized water droplets surrounded by oil serve as test tubes for chemical investigation of just a few molecules, report US researchers.
Daniel Chiu at the University of Washington at Seattle, who developed the technique, anticipates a wide range of applications. 'Anything you can do in the test tube we hope to be able to do in the droplet. We just don't need a lot of cells. We don't even need one cell, just a few molecules,' he said.
Chiu's group, whose work was presented at the American Chemical Society's national meeting in Washington DC, designed a microfluidics device with outlet channels for oil and water arranged to produce water droplets enclosed in the oil phase.
'The size of the droplet can be varied easily, and we typically work with ones that are in the femtoliter range, that is, droplets with diameters that are between one and 10 microns,' Chiu told Chemistry World.
The technique employs laser equipment to place biological or biochemical samples such as cells or protein molecules at the interface between the two channels, to ensure the sample gets encapsulated when the droplet forms.
The potential applications impress nanotechnologist Andrei Khlobystov at the University of Nottingham, UK. 'This method gives an excellent opportunity for studying interactions between complex molecules in a tiny volume, which could advance our understanding of the mechanisms of molecular self-assembly and molecular recognition,' said Khlobystov, who uses carbon nanotubes as test tubes (see Chemistry World, August 2004, p9; Chemistry World, December 2004, p7).
Julius Rebek, director of the Skaggs Institute for Chemical Biology at La Jolla, California, agrees: 'This is a big step - or should I say a tiny one ? - that brings the 'top down' approach closer to the 'bottom up' approach of molecular nanoscience.' Michael Gross