From man-made toxic chemicals such
as industrial by-products to poisons that occur naturally, a water or food
supply can be easily contaminated. And for every level of toxic material
ingested, there is some level of bodily response, ranging from minor illness to
painful certain death.
Biosensors have long been used to
safeguard against exposure to toxic chemicals. Food tasters employed by the
ancients acted as early versions of biosensors, determining if a meal had been
poisoned. More modern examples include the use of fish, which may alter their
swimming characteristics if a toxic material is introduced into to the water.
But although current warning systems are more sophisticated, they require
equipment and time that a soldier in the field or an adventurer in the
wilderness do not have.
Now Professor Yosi Shacham-Diamand, Vice Dean of Tel Aviv University’s Faculty
of Engineering, along with Professor
Shimshon Belkin of the Institute
of Life Sciences at the
Hebrew University of Jerusalem, has married biology and engineering to produce
a biosensor device called the “Dip Chip,” which detects toxicity
quickly and accurately, generating low false positive and false negative
readings. The Dip Chip contains microbes designed to exhibit a biological
reaction to toxic chemicals, emulating the biological responses of humans or
animals.
Converting
biological response to electricity
The biological reaction is converted into an electronic signal that can be read
by the user. When perfected for commercial applications, the chip might be
easily plugged into a mobile device to determine toxicity, says Shacham-Diamand.
The new chips are based on
genetically modified microbes developed in Belkin’s laboratory. When the
modified microbes are exposed to toxic or poisonous materials, they produce a
measurable biochemical reaction—and this is where Shacham-Diamand’s work
begins.
“In my lab, we developed a
method for communicating with the microbes, converting this biological response
to electrical signals,” he explains. The device, which looks like a dip
stick, immobilizes these specially-produced microbes next to the sensing
electrodes. Once the microbes come into contact with a questionable substance
they produce a chemical signal that is converted to an electrical current by an
device that can interpret the signals, producing a binary “toxic” or
“not toxic” diagnosis.
In the future, Shacham-Diamand
hopes that smaller versions of the Dip Chips might be plugged into existing
mobile electronic devices, such as cell phones or tablets, to give the user a
toxicity reading. This would make it an economically feasible and easy-to-use
technology for people such as campers or for military purposes.
Reading
any toxic material
One of the chip’s advantages is its ability to identify toxicity as a
biological quality instead of specific toxic chemicals. There are already
excellent detectors to identify specific toxic materials, says Shacham-Diamand.
The Dip Chip, however, is designed to alert the user to overall toxicity. And
because the chip measures general toxicity, it will pick up on any and all
toxic materials—even those that have not been discovered or invented yet.
Beyond their ability to find toxic
chemicals in the field, these chips can also be put to use in the cosmetics or
pharmaceuticals industries, says Shacham-Diamand. They could be used to detect
the toxicity of new compounds, minimizing the controversial use of lab animals.
Using the same technology, the researchers have also developed a larger-scale
device which allows water to flow continuously over the sensor, making it
appropriate for online, real-time monitoring of water supplies.
The results of their research have been published in a number of journals,
including Electrochimica
Acta and Sensors and Actuators B: Chemical.
