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Technology Promises Faster Diagnostic Tests

The Doctor-on-a-Chip technology has potential to revolutionize the field of medicine by providing quick and accurate test results.

Published March 1, 2003

By Bruce Tobin
Academy Contributor

Image courtesy of Toowongsa via stock.adobe.com.

Sending medical specimens off to labs can mean lengthy waits for results needed to make or confirm diagnoses. But help is on the way in the form of a developing nanotechnology called Doctor-on-a-Chip (DoaC).

In broad terms, DoaC technology will allow a sample of bodily fluid to be processed to test for a disease’s DNA marker. Research teams at universities in the United Kingdom and the United States are working on such devices. DoaCs will allow clinicians to perform many more medical diagnostic tests in their offices and in the field, and promise delivery of results in as little as 5 to 10 minutes.

At Brunel University in London, Professor Wamadeva Balachandran (Bala) heads a six-member research team working on a DoaC. In the United States, a team of 70 researchers led by Professor Chad A. Mirkin, of Northwestern University, is working on a similar program.

Bala believes the system of taking a patient sample and sending it to a lab – where it may takes days for the results to be determined and communicated back to the doctor – can be dangerous. “In certain cases it could be a life-and-death situation,” he said. “The idea here (with DoaC devices) is that doctors can get the results while still talking with their patient.”

In the DoaC concept, the doctor places a drop of the patient’s blood on the front end of a polymer chip and waits 5 to 10 minutes for the chip to do its tests and display the results. The device will initially be the size of a credit card, Bala said, and eventually the size of a microprocessor chip.

Faster Diagnostic Tests

Prof. Wamadeva Balachandran (Bala)

Going into more detail, Mirkin explained, “A sample (blood, saliva or urine) is processed through microfluidics (micro- or nano-scale devices for manipulating fluids). Then the marker DNA (for the diseases of interest) is delivered to the reader portion of the chip. If marker DNA binds to this portion of the chip…nanoparticle probes are used to develop the chip (also through microfluidics).” The readout device will measure the conductivity of the particles between microelectrodes.

Bala said the idea behind his device involves the Electric Field Manipulation of DNA (characterizing DNA using electrical fields to move them and then to look at their properties). His original thinking, three or four years ago, was that if you could identify various characteristics you could confirm a particular virus in terms of its properties.

“But, of course, during this period the genome sequencing has moved on so fast,” Bala explained. “Various medical colleagues were all saying that if there were a system, which could be easily utilized to detect viruses by GPs (general practitioners) in their offices, that would speed up the process of diagnosis and save a lot of lives.” So he decided to work on it. Bala’s idea now is to use this technique to move DNA into a chamber to look for a particular type of DNA linked to a virus. Once confirmed as the suspect DNA type, “it comes out of that chamber and we again use electrical techniques to categorize the DNA: electrical impedance, for example.”

Results in 5-10 Minutes

Prof. Chad A. Mirkin

The technology involved in the tests is nothing new. “The challenge is to bring the technique down to the microscale, to put it on a single chip,” Bala said, “and we’re doing that now.”

Processing the sample involves attaching probes to the DNA. The type of virus that’s suspected determines the type of probe that is used. The sample then goes through a polymerase chain reaction (PCR) and then through the chamber with the medium for dielectrophoretic measurement. It then passes through various dielectrophoretic chambers. “In 5-10 minutes the doctor will be able to look at his computer screen and know whether you have hepatitis A or hepatitis B, for example, or whether you don’t have any virus,” he said.

Early models of Bala’s chip will check for various kinds of viral infections sequentially, one virus type after another being tried until a match is found. Eventually, he expects DoaCs to have the ability to run through a whole series of tests for various viruses.

“The (DoaC) potential,” concludes Mirkin, “is enormous.”

Also read: Building a Big Future from Small Things


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