22 | NewScientist | 1 March 2014

Technology

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let the sun shine inA device powered by the sun’s rays could provide early diagnoses for a range of deadly diseases

Hal Hodson

THE power of the sun could spark a medical revolution. A device can diagnose diseases using little more than a smartphone, sunlight and a tiny DNA sample.

The KS-Detect, built by engineers at Cornell University in New York, will be used to diagnose Kaposi’s sarcoma, the AIDS-related cancer that killed Tom Hanks’s character in the film Philadelphia. Li Jiang and David Erickson, who developed the device, are testing it in Uganda, in partnership with Makerere University in Kampala.

Kaposi’s sarcoma is one of the most common forms of cancer across sub-Saharan Africa, caused by a herpes virus that takes advantage of weakened immune systems. It kills between a fifth and a third of those it infects within a year – and up to 70 per cent within three years. Late diagnosis is one of the main

factors contributing to the low survival rate. Cornell’s KS-Detect aims to change this.

Testing for the disease typically involves using the polymerase chain reaction (PCR) to amplify traces of the herpes virus DNA in the presence of a primer until there are enough copies to show up in a detector. But you need precision electronics to heat and cool the sample and drive the reaction.

The KS-Detect works without electricity by using a lens to focus the sun’s rays into a disc of light where the edges are cooler than the centre. A long microscopic channel is etched onto a chip that is placed under the disc of light. The sample moves along this channel so that its temperature changes in cycles, alternating between the heat at the centre of the light disc, and the cool edges. This drives the PCR. A dye called SYBR Green glows under blue light if amplified DNA from the herpes virus is detected. A smartphone

controlling the chip then reads the results.

“We thought why not go straight to the source and use sunlight directly as heat, skip the electricity?” says Jiang. “That let us skip a lot of the components you need in normal PCR.”

Francis Moussy of the World Health Organization in Geneva, Switzerland, is impressed. With such a device people can be tested where they live. “It’s really important to bring diagnostics to

“ A trapped person can write a 27-character message such as ‘broken leg stuck in a bank’ ”

–PCR for all, no electricity required–

the patients instead of making the patients travel,” he says.

Moussy, who works on new medical diagnostic technologies for the WHO, says the device can be adapted to detect other diseases. All that’s needed is to change the primers so that different kinds of DNA can be amplified. “PCR is used for the detection of TB [and] can be used for many non-communicable diseases. It’s a tool that’s becoming more and more useful.” n

Turn your phone’s Wi-Fi hotspot into a cry for helpAN APP that turns a smartphone into a wireless SOS beacon could one day help rescuers track down people who have been trapped in buildings after natural disasters or bombings.

Because such events often knock out phone and internet networks, trapped people cannot make calls, send texts or email for help. “They are in an island of non-connectivity,” says

Amro Al-Akkad, an engineer with the Fraunhofer Institute for Applied Information Technology in St Augustin, Germany.

Then his colleague, Leonardo Ramirez, noticed that if his neighbours changed the name of their home Wi-Fi network, it doubled as an opportunity to send a message, such as “No smoking on the balcony”. He realised that you could use an app to insert a short SOS message into the name field of a phone’s Wi-Fi hotspot, too, as these can broadcast a radio signal without requiring internet access. Rescuers can then read the

message with their own Wi-Fi app.The team consulted emergency

workers from the Haiti and Fukushima disasters and developed a “victim app” and a “seeker app”. “They wanted it simple, unencrypted and smart,” says Al-Akkad.

With the victim app a trapped person can write a 27-character message such as “broken leg stuck in bank” or “need help fire on bus” and a

seeker app up to 100 metres away can pick it up. The app found two “trapped” people in a large-scale, simulated terrorist attack at a seaside chemical plant in Stavanger, Norway. The team will present the apps at a computer conference in Toronto, Canada, in April.

They hope the victim app will be incorporated in Android or iOS operating systems, but they are also patenting a way to distribute the app virally at a disaster scene. “We need this as no one expects to be in a disaster and won’t download the app,” says Al-Akkad. Paul Marks n

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