Physicists in France have shown that it is possible to detect DNA with a purely electronic technique. Ulrich Bockelmann and colleagues at the Ecole Normale Supérieure in Paris measured the intrinsic charge of DNA molecules with an array of silicon transistors, which allowed them to avoid the markers and labels used in conventional detection techniques. The team has already used its device to detect and identify a common genetic mutation in human DNA, and hopes to exploit the approach in lab-on-a-chip applications (F Pouthas et al. 2004 Appl. Phys. Lett. 84 1594).
Bockelmann and colleagues exploited the fact that most biological molecules are charged in solution by building an array of 100 field-effect transistors (FETs) that were spaced tens of microns apart. Each transistor had an active surface area of tens of microns squared and was covered by a layer of silicon dioxide 10 nanometres thick.
The group placed the biomolecules on the surface of the array and measured the electronic properties of each transistor in the network. DNA molecules produce a negative shift in potential between the source and drain electrodes in the transistors because they are negatively charged in aqueous solution. By measuring the size of this potential shift, it is possible to identify the molecules in the solution.
Bockelmann and co-workers demonstrated the sensitivity of the technique by detecting and identifying a genetic mutation called 35delG that is responsible for hereditary deafness. The detection of specific mutations relies on the use of a polymerase chain reaction to increase the size of the sample.
