March 1, 2006 5:54 AM PST
Sensor instantly detects cocaine in blood
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The group, which includes scientists from the University of California at Santa Barbara, a Nobel prize winner and two high school students, said the sensor could also conceivably be used to test for exposure to biotoxins and other substances.
The sensor contains a specific, artificially fabricated DNA molecule that reacts when it meets cocaine. In seconds, the molecule turns from a floppy, formless shape into a rigid structure. When adding a blood or saliva sample contaminated with cocaine to the sensor, the change can be instantly measured by sending electrons through the DNA and seeing how they travel.
"The sensor can be built into a portable, handheld platform, and (the test) can be done here, in real time, within a few minutes, not a few hours," said Alan Heeger, a UCSB physics professor and Nobel Prize winner, who is part of the research team.
The testing device can be built from existing, inexpensive electronics. Heeger said the sensor is a major improvement on today's drug tests, where a sample of blood or urine has to be separated into its components before drugs can be identified. This takes a few hours and requires the tests to be sent to a well-equipped laboratory.
Heeger, who won the Nobel Prize for chemistry in 2000 for the discovery and development of conductive polymers, said the research behind the sensor has other potential applications.
"There are a number of areas where you could use such a biosensor--in preventing bioterrorism, for example," he said. That is because the sensor could be based on other DNA molecules that bind to different substances, such as biological warfare agents.
Kevin Plaxco, a UCSB biochemistry professor and head of the research project, said that some of the most important potential applications lie within health care. For example, the sensor could be used to detect proteins associated with diseases or monitor levels of pharmaceutical drugs in a patient's blood.
"There are a lot of drugs right now that are very difficult and, in some cases, impossible to use because different people metabolize them differently. The same dose could be fatal for one person and therapeutic for the next," he said.
Two of the contributors to the project are high school students who came for a lab internship last summer.
"I must admit I wasn't expecting much to come from this, but these two young women were really very good. They collected quite a bit of the data that we used, so in fact they are co-authors on this paper," Plaxco said. An article describing the research was published in the Journal of the American Chemical Society on Feb. 18.
McCall Wood and Elaine Doctor were assigned to measure the sensitivity of the sensor.
"It was a lot of pressure. Our mentor had to teach us stuff that it would take a regular college student a week to learn within hours," said Doctor, a senior at Oxnard High School in California who is interested in a career in biotechnology.
"I feel honored to help America's war on drugs," she said.
Industry has already shown interest in the results. "Patent pending, we are talking to several companies interested in licensing it," Plaxco said.
The sensor can currently detect levels of 3 parts per million of cocaine in blood. The research team is now working to refine the sensor by increasing its sensitivity to smaller concentrations of cocaine, since people are considered "stoned" when cocaine concentration is equal to .3 parts per million.
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