It’s being called a “lab on a chip.” A credit card-sized plastic chip can test blood samples – as little as 1 microliter – for HIV and syphilis, and it only takes 20 minutes to do it. The chip has already been field tested. A recent report in Nature Medicine documents the chip’s success in detecting HIV and syphilis in Rwanda. The cheap cost of the chip, testing, along with its mobility and durability could have a profound affect on the detection and treatment of infectious diseases in impoverished countries all over the world.
The so-called ‘mChip’ brings together microfluidics – the manipulation of small volumes of fluids – and nanotechnology to simplify and improve a technology called ELISA that is commonly used in developing countries to detect infection. But running an ELISA requires large equipment, microscopes and computers. Feasible for many clinics and research labs in developed countries, but impossible for remote clinics in resource-limited countries. Consequently testing in these countries typically involves sending blood samples to a far away lab and waiting for results. It’s a process that can take days or weeks. For many people in developing countries the trip to the nearest clinic can itself take days, and too often people don’t come back for the return trip to get the results. mChip could provide a cheap and easy way to test for infectious diseases at remote clinics.
The chip itself is an injection molding within which are a series of microfluidic channels. There are different loops along the channels that act as miniature test tubes, containing chemicals and nanoparticles that can detect substances found in HIV- and syphilis-infected blood. Because these test tube areas are separate from each other the same chip can be used to detect both HIV and syphilis. The one microliter of blood needed makes it easy to test even newborns, an essential test in areas where infections are all too often passed on from mother to baby. A plastic tube containing the blood sample and chemical reagents attaches to the chip and its contents are pulled through the chip with a syringe. The results are ready in just 20 minutes and can be read by medical personnel right there in the clinic. Samuel Sia, assistant professor of biomedical engineering at Columbia University, headed the team that built mChip. He explains how the chip works in the following video.
There are other tests which are more mobile and quicker than ELISA. Much like a pregnancy test, these ‘lateral flow’ tests involve a strip of paper upon which a colored band is read. However, lateral flow tests are not consistently accurate across different types of infection and environmental settings. Developing countries typically stick with ELISAs.
Rather than simply improve upon existing technologies, Sia’s was an explicit vision to help people with severely-limited resources by making something cheap and easy to use. The chips themselves cost about $1 and each and the device to read them about $100. As Sia said in a press release, “Diagnosis of infectious diseases is very important in the developing world. When you’re in these villages, you may have the drugs for many STDs, but you don’t know who to give treatments to, so the challenge really comes down to diagnostics.”
Sounds great, but will it work in the field the way it’s supposed to? The great news is that the mChip has already been field tested. A recent report in Nature Medicine documents a four year trial in which mChip was used to diagnose hundreds of patients in Rwanda. The chip detected 100 percent of HIV-positive patients while only a single false positive out of 70 total samples. When they ran HIV and syphilis tests simultaneously mChip again detected all of the HIV-positive and 94 percent of the syphilis-positive patients, although false-positives for syphilis was 4 out of 67 total samples. Not perfect, but the accuracy is comparable to conventional tests run in the lab. Sia deemed it a victory. “We’ve taken what’s long been a great theoretical concept and shown that it can be done in the field,” he told the Washington Post. Doris Rouse, an RTI International vice president who is an expert on global health technologies and who was not involved in the study, told the Post, “This is a big step. What’s especially exciting about this device is that it’s rugged, easy to use, and doesn’t require a lot of infrastructure or training.”
Anything to cut down on costs of and time between testing and treating infections will help a place like Rwanda enormously. About three percent of Rwanda’s population is infected with HIV. In the capital city of Kigali as much as eight percent of women are HIV-positive. Sia hopes that pregnant women might benefit from mChip and receive treatment when they would otherwise remain undiagnosed. Because they are also distinguished by unique chemical markers, Sia says mChips could potentially be developed to test for hepatitis B and C, and sexually transmitted infections such as herpes, chlamydia, and gonorrhea.
The lab-on-a-chip technology is not limited to detecting infectious diseases. As others are attempting, Sia has used mChip technology to develop an assay for prostate cancer. Developed in collaboration with Claros Diagnostics Inc., a company Sia co-founded in 2004, the prostate chip was approved for use in Europe last year. That same year MIT’s Technology Review named Sia one of the world’s top young investigators for 2010.
Despite the trial’s promising results, it may be some time before mChips are dispersed to clinics in countries like Rwanda that desperately need them. It all comes down to money. While it makes perfect sense to fund the research with government grants, finding private investors who view mChip as profitable will be much more difficult. Sia doesn’t see his prototype going forward for another two or three years yet. “The challenge now is how to go from an academic study to distributing this test in the field.” Hopefully governments and nonprofits, like the Gates foundation which has already invested in Sia’s company, can step up and give mChip the means to get out of the lab and into the field. Rarely does a new technology hold such promise for the immediate and profound betterment of society. It would be a shame to watch it stall and people go untreated because the monetary incentives aren’t as compelling as the humanitarian ones.