Credit: Image courtesy of J. W. Hong.

Forget cell sorters, minipreps, electrophoretic gels and beakers full of reagents; researchers have now found a way of carrying out the whole procedure — from single cell to purified DNA or mRNA — on a microchip that contains only nanolitre amounts of fluid.

The secret of creating this diminutive laboratory lies in an ingenious 'microfluidic chip' — this is a clear, rubbery square the size of a postage stamp on which an intricate number of channels are cast, each only the width of a human hair (see figure). The clever use of valves, which are operated hydraulically, allows fluids from different chambers to be mixed and reactions to take place in a versatile and controlled way. For example, a DNA-purification experiment might start by mixing the contents of three channels that are loaded with dilution buffer, cells and lysis buffer; the lysed cells can then be directed to a DNA-affinity column and purified, and the eluted DNA is recovered at the end. Cross-contamination simply does not occur, so different reactions can be processed in parallel — an innovative feature that was illustrated by simultaneously purifying genomic DNA from three bacterial populations.

Other than allowing you to say that you are carrying your benchtop in your lab-coat pocket, what practical purpose might this technology have? The ability to isolate nucleic acid from a single cell is an original aspect of the technique, and means that cells that are impossible to culture, or that would be modified by such a procedure, can be analysed. This feature can also be exploited to create cDNA libraries from a single cell. But the design of the chip itself has uses that go beyond the molecular genetics laboratory. Fiddle with the channel plumbing system and the nanolab is transformed into a computer or a protein-crystallography chamber.