As antiretroviral drugs that treat HIV have become more
commonplace, the incidence of Kaposi's sarcoma, a type of cancer linked to
Aids, has decreased in some countries.
The disease, however, remains prevalent in sub-Saharan
Africa, where poor access to medical care and lab tests only compound the
problem. Now, Cornell University engineers have created a new smartphone-based
system, consisting of a plug-in optical accessory and disposable microfluidic
chips, for in-the-field detection of the herpes virus that causes Kaposi's.
"The accessory provides an ultraportable way to
determine whether or not viral DNA is present in a sample," says
mechanical engineer David Erickson, who developed the technique along with his
graduate student, biomedical engineer Matthew Mancuso.
The technique could also be adapted for use in detecting a
range of other conditions, from E-coli infections to hepatitis.
How it works
Unlike other methods that use smartphones for diagnostic
testing, this new system is chemically based and does not use the phone's
built-in camera. Instead, gold nanoparticles are combined (or
"conjugated") with short DNA snippets that bind to Kaposi's DNA
sequences, and a solution with the combined particles is added to a
In the presence of
viral DNA, the particles clump together, which affects the transmission of
light through the solution. This causes a colour change that can be measured
with an optical sensor connected to a smartphone via a micro-USB port. When
little or no Kaposi's virus DNA is present, the nanoparticle solution is a
bright red; at higher concentrations, the solution turns a duller purple,
providing a quick method to quantify the amount of Kaposi's DNA.
The main advantage of the system compared to previous
Kaposi's detection methods is that users can diagnose the condition with little
training. "Expert knowledge is required for almost every other means of
detecting Kaposi's sarcoma," Mancuso says. "This system doesn't
require that level of expertise."
Erickson and Mancuso are now collaborating with experts on
Kaposi's at New York City's Weill Cornell Medical College to create a portable
system for collecting, testing, and diagnosing samples that could be available
for use in the developing world by next year. The team's start-up company,
vitaMe Technologies, is commercializing similar smartphone diagnostic
technologies for domestic use.
Detecting Kaposi's sarcoma is not the only goal, Mancuso
says. "Nanoparticle assays similar to the one used in our work can target
DNA from many different diseases," such as methicillin-resistant
Staphylococcus aureus (MRSA), a bacterium responsible for several
difficult-to-treat infections in humans, and syphilis.
The smartphone reader could also work with other colour-changing
reactions, such as the popular enzyme-linked immunosorbent assays (ELISA), a
common tool in medicine to test for HIV, hepatitis, food allergens, and E.
coli. The lab also has created smartphone accessories for use with the colour-changing
strips in pH and urine assays.
"These accessories could form the basis of a simple,
at-home, personal biofluid health monitor," Mancuso says.