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鈥檚 sarcoma, the AIDS-related cancer that killed Tom Hanks鈥檚 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鈥檚 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 鈥� and up to 70 per cent within three years. Late diagnosis is one of the main factors contributing to the low survival rate. Cornell鈥檚 KS-Detect aims to change this.
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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鈥檚 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.
鈥淲e thought why not go straight to the source and use sunlight directly as heat, skip the electricity?鈥� says Jiang. 鈥淭hat let us skip a lot of the components you need in normal PCR.鈥�
Francis Moussy of the World Health Organization in Geneva, Switzerland, is impressed. With such a device people can be tested where they live. 鈥淚t鈥檚 really important to bring diagnostics to the patients instead of making the patients travel,鈥� 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鈥檚 needed is to change the primers so that different kinds of DNA can be amplified. 鈥淧CR is used for the detection of TB [and] can be used for many non-communicable diseases. It鈥檚 a tool that鈥檚 becoming more and more useful.鈥�
This article appeared in print under the headline 鈥淟et the sun shine in鈥�
