Scientists in Korea are using convection to power quick and portable device for genetic point of care diagnostics. 

The most popular ways to diagnose of infectious diseases and pathogens are using immunological methods or the detection of nucleic acids (DNA or RNA) by polymerase chain reaction (PCR). The PCR method is more sensitive but miniaturisation of the equipment to make it convenient swift and portable has proved a challenge. 

'Genetic diagnosis requires three sequential steps: DNA sample preparation, amplification (typically PCR), and detection. Accordingly, portable PCR is one of the necessities for genetic point of care tests,' explains Choi. PCR uses cycles of repeated heating and cooling of the reaction mixture for DNA melting and enzymatic replication of the DNA. 

Choi's system is made up of a loop of thin plastic on a polymer chip. Convection is used to move the reaction mixture through the different temperature zones in the loop, removing the need for an external pump. The time taken for the mixture to flow around the loop can be controlled by varying the angle of the chip. This simplification makes the chip more robust, and easily disposable. Also it works faster than conventional PCR, giving results in 10 minutes compared to the 71 minutes that it takes a conventional machine, says Choi. 

But Choi still sees scope for improvement and is now working on smaller, faster devices and on developing the other steps in genetic diagnosis. He envisages a high performance system the size of a mobile phone for use in a variety of fields, from medicine to environmental monitoring. 

Laura Howes 

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