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Sensor100
February 2016
Hand-held Biosensor Uses a Component of DNA to
DetectTraces of Gold inWater
The gold sensor is the latest in a series of metal-de-
tecting biosensors under development by Rebecca
Lai, an associate professor of chemistry at the Uni-
versity of Nebraska-Lincoln. Other sensors at vari-
ous stages of development detect mercury, silver or
platinum. A primary purpose for the sensors would
be to detect water contaminants, Lai said.
DNA, the carrier of genetic information in nearly all
living organisms, might seem an unlikely method to
detect gold and other metals. Lai’s research, how-
ever, exploits long-observed interactions between
metal ions and the four basic building blocks of
DNA: adenine, cytosine, guanine and thymine. The
gold sensor, for example, is based on gold ions’
interactions with adenine.
Lai’s sensor works by measuring electric current
passing from an electrode to a tracer molecule,
methylene blue in this case. In the absence of Au(III),
the observed current is high, because the oligoad-
enine probes are highly flexible and the electron
transfer between the electrode and the tracer molecule is efficient. But upon binding
to Au(III) in the sample, the flexibility of the oligoadenine DNA probes is hindered, re-
sulting in a large reduction in the current from the tracer molecule.The extent of the
change in current is used to determine the concentration of AU(III) in the sample.
University of Nebraska
News Release17 February
The DNA probe is immobilized on
a gold electrode contained within
the circle. A water sample as
small as 10 microliters is applied
to the sensor through the center
of the crystal cube. The white,
green and red leads attached to
the contact pads connect to a
handheld power source.