Drug metabolism studies can be conducted on smaller samples than before thanks to an on-chip electrochemical cell designed by European scientists.

Electrochemical cells can mimic the oxidative metabolism of drugs within the body. By coupling them to mass spectrometers or liquid chromatographs, scientists can detect and identify the metabolites.

Mathieu Odijk, at the University of Twente, Enschede, the Netherlands, and colleagues made a glass chip containing the usual three electrodes found in an electrochemical cell - the working, reference and counter electrodes - plus an extra sensing electrode to detect generated species. They connected the chip to a liquid chromatography-mass spectrometry (LC-MS) system. When they injected a solution of amodiaquine, an antimalarial drug, through the chip, they showed that the cell oxidised the drug, forming all its major metabolites, which were detected by LC-MS.

Other electrochemical cells are commercially available but Odijk says his uses much smaller sample volumes. 'With this chip, new drugs can be studied faster and with more ease,' he says. He adds that the counter electrode is located in a separate side-channel from the other electrodes, which prevents unwanted side products appearing in the measured spectrograms.

'This chip is used in combination with tools like LC and electrospray-MS. A very logical but technically challenging next step is to combine these three tools onto a single lab-on-chip, while keeping the fabrication costs within acceptable limits,' says Odijk.

Madelaine Chapman

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