The discovery that all life is underpinned by a genetic code has changed our understanding of everything in biology. And yet, given that DNA is thousands of times smaller than a human hair, most of the applications that involve its use have remained restricted to sophisticated labs.
No longer. Over the past decade, miniaturization of computers and lab equipment has made high-tech tools portable. The latest such advancement is the stuff of science fiction: a group of scientists in the US and Sweden have developed a DNA-analyzing kit that can run on a smartphone.
To understand how it works, consider the example of tuberculosis. When a patient in, say, rural India is diagnosed with the disease, a doctor without access to a sophisticated lab will typically give the patient drugs from the first line of treatment. However, one in four patients won’t respond to this treatment, because the bug they’ve caught is resistant to these drugs.
Without a test to determine which strain the patient is suffering from in advance, the doctor has to wait for weeks till she finds out that the patient has the drug-resistant infection, and then prescribe a different medication. In that period, the patient would have already spread the infectious and hard-to-treat disease to many more people around him.
A portable DNA analyzer could fix this problem. To create one, Mats Nilsson of Stockholm University and his colleagues took a sample of human tissue and analyzed it with a specially designed attachment connected to a Nokia Lumia 1020 smartphone.
DNA is made up of four bases: A, T, G, and C, and a tuberculosis genome consists of typically 4.5 million base pairs. But Nilsson only needs to look at a tiny section of the whole genome. Inside the attachment, specialized chemicals are designed to seek that tiny sequence of DNA and snip it out.
DNA is too small for simple smartphone cameras to capture. So an enzyme is used to multiply the small snippet 1,000 times. Next, a new set of chemicals, which become fluorescent when light is shone on them, attach themselves to it based on what the sequence is.
Finally, the attachment shines two different colors of laser onto the mixture. With all those DNA snippets emitting light, a decent smartphone camera is now able to see DNA. If the tuberculosis strain is drug-resistant, the mixture shines in a different color than if the infection is not drug-resistant. All this can happen in a few hours, rather than the days or weeks that would be needed to send the sample to a specialized lab for the same result.
“I was so surprised,” says Nilsson, “the images from the smartphone and those from the lab were indistinguishable.” The study’s results were published in Nature Communications.
Nilsson’s team is now looking to commercialize the technology. The researchers believe that the attachment could cost as little as $500, compared to the many thousands of dollars needed for lab equipment.
There are still limitations. The lab has yet to develop a method that engineers the movement of various liquids that go in and out of the attachment. To show their system works, the researchers used lab equipment to do it. And at present, the system can only test for one type of disease at a time. So if you want to test for cancer after a tuberculosis test, you’d have to wash the equipment and use a whole different set of chemicals to perform the analysis.
Nilsson has yet to try it, but he thinks it should be possible to adapt the attachment for different smartphones, even those with lower-resolution cameras. The Nokia Lumia 1020 has a 41-megapixel camera, whereas typical smartphone cameras in the latest generation use just 12 megapixels.
The project also faces competition. A UK-based company, Oxford Nanopore, has developed a technology that doesn’t rely on cameras to achieve a similar analysis. It is in the process of creating a smartphone adapter for it. The system promises to be even more portable, because it won’t require the use of specialized chemicals. Clive Brown, the company’s chief technology officer, told the BBC that it would “allow anybody to sequence anything, anywhere.”