Chip spots DNA electrochemically

DNA chips contain arrays of DNA fragments, or probes, that bind to target DNA strands in order to spot the genetic fingerprints of disease-causing mutations or microbes.

Existing methods of reading DNA chips use fluorescent molecules and relatively expensive microscopes. DNA chips, which promise to enable outside-the-laboratory use of DNA detectors, including applications like detecting pathogens at clinics, require a less cumbersome method of finding out which microscopic spots of immobilized DNA probes have bound to target DNA strands.

Researchers from University of Bochum and Friz Biochem in Germany have devised a microelectrochemical method of reading DNA chips that could be used in portable detectors. The researchers showed that when DNA probes are attached to a gold electrode, a scanning electrochemical microscope can detect the chemical changes that occur when when the probes attach to target DNA strands.

Ferrocyanide ions in liquid between the microscope's platinum tip and the gold electrodes enhance the flow of electrical current between them. DNA is negatively charged and so repels the negatively-charged ions, diminishing the current. When a DNA probe attaches to a target strand, the double-strand reduces the current further.

The researchers plan to build a device that aligns an array of platinum tips over an array of gold electrodes in order to detect many types of DNA at once.

The researchers' method could be used practically in two to five years, according to the researchers. The work appeared in the June 25, 2004 issue of Angewandte Chemie International Edition.