Engineers from Cornell University have created a new optical sensor that plugs in to a smart phone and, using disposable micro-fluidic chips, allows for in-the-field detection of the herpes virus that causes Kaposi’s sarcoma, a cancer linked to AIDS. As antiretroviral drugs that treat HIV have become more commonplace, the incidence of Kaposi’s sarcoma has decreased in the US. The disease, however, remains prevalent in sub-Saharan Africa, where poor access to medical care and lab tests only compound the problem.
According to mechanical engineer Professor David Erickson of the Sibley School of Mechanical and Aerospace Engineering at Cornell University who developed the technique along with his graduate student, biomedical engineer Matthew Mancuso, the accessory provides a portable way to determine whether or not viral DNA is present in a sample. The technique could also be adapted for use in detecting a range of other conditions, from E. coli infections to hepatitis. Mancuso will describe the work at the Conference on Lasers and Electro-Optics (CLEO) 2013 taking place 9-14 June at the San Jose Convention Centre in San Jose, California (US).
Unlike other methods that use smart phones 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 micro-fluidic chip. 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 smart phone via a micro-universal serial bus (USB) port.
When little or no Kaposi’s virus DNA is present, the nanoparticle solution is bright red; at higher concentrations, the solution turns a duller purple (see photo 1 at top of page). This provides 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.
Photo 2: The addition of target viral DNA causes the nanoparticles to form aggregate “clumps,” which leads to a change in their colour. Credit: Matthew Mancuso.
Prof. Erickson and Mancuso are now collaborating with experts on Kaposi’s at New York’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 smart-phone diagnostic technologies for domestic use.
Detecting Kaposi’s sarcoma is not the only goal for these accessories, Mancuso says. DNA from many different diseases can be targeted with this smart-phone accessory. For example, DNA from methicillin-resistant Staphylococcus aureus (MRSA), which is a bacterium responsible for several difficult-to-treat infections in humans, can be targeted, as can syphilis DNA.
Photo 3: Maps generated using smart-phone-enabled GPS tagging of diagnostic results could enable health professionals to track the spread of infectious disease in the future. Credit: Matthew Mancuso.
The smart-phone reader could also work with other colour-changing reactions, such as the popular enzyme-linked immune-sorbent assays (ELISA), a common tool in medicine to test for HIV, hepatitis, food allergens and E. coli. The lab also has created smart-phone accessories for use with the colour-changing strips in pH and urine assays. Mancuso says that these accessories could create the basis for a simple, at-home, personal bio-fluid health monitor.
Prof. Erickson will give the CLEO 2013 presentation AM3M.2 “Smartphone Based Optical Detection of Kaposi’s Sarcoma Associated Herpes Virus DNA” at 2:00 p.m. on Monday, 10 June at the Marriott San Jose.
Photo 1: Gold nanoparticle conjugates change from bright red to dull purple with the addition of target viral DNA. Credit: Matthew Mancuso.