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DNA has formed the backbone of self-assembling logic circuits designed by a team at Duke University. To communicate, the circuits employ light-emitting molecules already widely used by biologists in their own experiments.

Chris Dwyer, assistant professor of electrical and computer engineering at Duke’s Pratt School of Engineering, said the technique could be used to build intelligent but tiny biosensors as well as nanoscale encryption keys.

Dwyer said the logic is form of diode-diode logic, one of the earliest approaches to digital computation used in electronics. Although it cannot form all the possible Boolean logic gates, it can be used to build simple computers from AND and OR gates. In the Duke University scheme, the diodes of an electronic circuit are replaced with chromophores - light-absorbing elements - attached to segments of DNA.

DNA-linked chromophores, particularly those that fluoresce, are used widely in biological experiments as they make it easy to identify the locations of genetic elements within a cell. Theodor Förster found in 1948 that chromophores can pass energy to other, different chromophores close by through a coupling process. Biologists often use this in Förster or fluorescence resonance energy transfer (FRET) to show when molecules such as proteins are coupled together in complexes.

Philips Magnotech troponin sensor artist's impressionA recent Nanosensors KTN seminar held at the National Physical Laboratory in Teddington provided an opportunity to show how biotech, nanotechnology and electronics are being combined in a new generation of portable instruments. Dion Klunder, a scientist at Philips Research, described the trade-offs that go into taking a technology that uses small particles and putting it into something that can be used in the field.

Although the original plan was to use the Magnotech system as a drug detector that could be used by police in the same way they would use a breathaliser, the emphasis has switched at Philips to speeding up the diagnosis of medical conditions, kicking off with heart attacks. Bedside staff can use instruments like that to work out quickly what treatment the patient needs.

“If possible, you want to stratify patients in the ambulance,” said Klunder. “In that way you can enable minimally invasive medicine.”

The reality today is that it takes a while to get the results back from a central laboratory. Although the actual tests are quick, the delay lies in the amount of time it takes to get the sample there and the result back, on top of the time that a sample may have to wait before being processed.

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