University of Illinois at Urbana-Champaign researchers have
developed a cradle and app for the iPhone 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, 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.
“We’re interested in biodetection that needs to be performed
outside of the laboratory,” said team leader Brian Cunningham, a professor of
electrical and computer engineering and of bioengineering at the U. of I.
How it will work
“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. A lot of medical conditions might be
monitored very 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. The cradle holds the phone’s camera in alignment with the
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 colour 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. For now, 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. The researchers are working to improve the manufacturing process for
the iPhone cradle and are working on a cradle for Android phones as well. They
hope to begin making the cradles available next year.
New app to test
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.
“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
multi-mode biosensor. We’ll use the phone and one cradle to perform four of the
most widely used biosensing assays that are available.”