Test for toxins in the field using a smartphone app

Researchers at the University of Illinois use the iPhone camera and processing power as a biosensor to detect toxins

An app for the iPhone could be used to detect toxins, proteins, bacteria and viruses in the field

Researchers and doctors in the field could soon run on-the-spot tests for environmental toxins, medical diagnostics and food safety using their smartphones.

Scientists at the University of Illinois at Urbana-Champaign have developed a cradle and app for the iPhone that uses the built-in camera and processing power of the phone as a biosensor to detect toxins, proteins, bacteria, viruses and other molecules.

Having such biosensing capabilities in the field could enable on-the-spot tracking of groundwater contamination, combine the phone’s GPS data with biosensing data to map the spread of pathogens, or provide immediate and inexpensive medical diagnostic tests in field clinics, or contaminant checks in the food processing and distribution chain, the researchers said.

'We’re interested in biodetection that needs to be performed outside the laboratory,' said team leader Brian Cunningham, a professor of electrical and computer engineering and of bioengineering at the University of Illinois.

'Smartphones are making a big impact on our society – the way we get our information; the way we communicate. And they have really powerful computing capability and imaging,' he says.

'Many medical conditions might be monitored inexpensively and non-invasively using mobile platforms like phones. They can detect molecular things, like pathogens, disease biomarkers or DNA, things that are currently only done in big diagnostic labs with lots of expense and large volumes of blood.'

The wedge-shaped cradle contains a series of optical components – lenses and filters – found in much larger and more expensive laboratory devices.

Many medical conditions might be monitored inexpensively and non-invasively using mobile platforms like phones

The cradle holds the phone’s camera in alignment with the optical components. At the heart of the biosensor is a photonic crystal, which is like a mirror that only reflects one wavelength of light while the rest of the spectrum passes through. When anything biological attaches to the photonic crystal – such as protein, cells, pathogens or DNA – the reflected colour will shift from a shorter to a longer wavelength.

For the handheld iPhone biosensor, a normal microscope slide is coated with the photonic material. The slide is primed to react to a specific target molecule. The photonic crystal slide is inserted into a slot on the cradle and the spectrum measured. Its reflecting wavelength shows up as a black gap in the spectrum. After exposure to the test sample, the spectrum is re-measured. The degree of shift in the reflected wavelength tells the app how much of the target molecule is in the sample.

The entire test takes only a few minutes; the app walks the user through the process step by step. Although the cradle holds only about US$200 of optical components, it is said to perform as accurately as a large $50,000 spectrophotometer in the laboratory.

In a paper published in the journal Lab on a Chip, the team demonstrated sensing of an immune system protein, but the slide could be primed for any type of biological molecule or cell type. The researchers are now working to improve the manufacturing process for the iPhone cradle and are also working on a version for Android phones. They hope to start making the cradles available next year.

Cunningham’s group recently received a grant from the National Science Foundation (NSF) to expand the range of biological experiments that can be performed with the phone, in collaboration with Steven Lumetta, a professor of electrical and computer engineering and of computer science at the University of Ilinois.

'It’s our goal to expand the range of biological experiments that can be performed with a phone and its camera being used as a spectrometer,' Cunningham said.

'In our first paper, we showed the ability to use a photonic crystal biosensor, but in our NSF grant, we’re creating a multimode biosensor. We’ll use the phone and one cradle to perform four of the most widely used biosensing assays that are available.'