How to convert an iPhone into a handheld biosensor
May 27, 2013
University of Illinois at Urbana-Champaign researchers have developed a cradle and app for the iPhone (Android version in the works) that uses the phone’s built-in camera and processing power as a biosensor to detect toxins, proteins, bacteria, viruses and other molecules.
Having such sensitive biosensing capabilities in the field could enable on-the-spot tracking of groundwater contamination, map the spread of pathogens (using the phone’s GPS), provide immediate and inexpensive medical diagnostic tests in field clinics, and contaminant checks in the food processing and distribution chain.
“A lot of medical conditions might be monitored very inexpensively and non-invasively using mobile platforms like phones,” said team leader Brian Cunningham, a professor of electrical and computer engineering and of bioengineering at the U. of I. “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.”
How it works
The wedge-shaped cradle contains a series of optical components — lenses and filters — found in much larger and more expensive laboratory devices. The cradle holds the phone’s camera in alignment with the optical components.
At the heart of the biosensor is a photonic crystal. A photonic crystal 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 color will shift from a shorter wavelength 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 $200 of optical components, it performs as accurately as a large $50,000 spectrophotometer in the laboratory. So the device is not only portable, but also affordable for fieldwork in developing nations.
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.
A multi-mode biosensor
Cunningham’s group is now collaborating with other groups across campus at the U. of I. to explore applications for the iPhone biosensor. The group recently received a grant from the National Science Foundation 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 U. of I. They are also are also working with food science and human nutrition professor Juan Andrade to develop a fast biosensor test for iron deficiency and vitamin A deficiency in expectant mothers and children.
In addition, Cunningham’s team is working on biosensing tests that could be performed in the field to detect toxins in harvested corn and soybeans, and to detect pathogens in food and water.
“In our NSF grant, we’re creating a multi-mode biosensor,” said Cunningham. We’ll use the phone and one cradle to perform four of the most widely used biosensing assays that are available.”
Cunningham also is affiliated with the Institute for Genomic Biology, the Beckman Institute for Advanced Science and Technology, and the Micro and Nanotechnology Laboratory, all at the U. of I.