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
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.
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