A few years ago University of California, Berkeley, professor Daniel Fletcher challenged the undergraduate students in his optics and microscopy course to develop an instrument using only a cell phone and a few objective lenses. It was not until after the project began that Fletcher and the students realized they had created a powerful yet inexpensive instrument that could potentially be used to test for diseases common in developing countries, such as malaria, sickle-cell anemia and tuberculosis.
These diseases in particular have wreaked havoc in Africa. In 2003 in the 10 African countries with available data, 11,875,108 people had malaria, according to the World Health Organization (WHO). Approximately 300,000 infants are born in Africa each year with sickle- cell anemia, and tuberculosis is the leading killer of people with HIV and in 2007 alone infected an estimated 1.9 million people in sub-Saharan Africa.
Financial limitations prevent the diagnosis and treatment of these diseases. According to Dina Sigano, a research scientist who has volunteered at missionary hospitals in Kpele Tsiko, Togo, in west Africa and Andhra Pradesh in India, "Getting functioning equipment like the light microscopes needed to identify malaria is a challenge. " Laboratory-grade versions cost thousands of dollars, and Sigano notes that once equipment is purchased there is no money to maintain and repair it.
Fletcher and his colleagues believe that their device, which they call the CellScope, will provide an inexpensive alternative to the microscopes. The group made a removable adapter that fits over the camera lens on a standard Nokia N73 cell phone. David Breslauer, lead author on the study published in PLoS One, demonstrates the adapter in a video on the university's Web site. It comprises inexpensive standard microscope eyepieces and objective lenses, along with high-power LEDs, which illuminate the object.
To determine the usefulness of the CellScope, the group obtained and analyzed samples from patients confirmed to have malaria and sickle-cell anemia. Petri dishes containing each sample were clipped onto the end of the adaptor and magnified by the lenses. The phone's camera captured the enlarged images of the cells. The malaria-infected blood cells had turned blue with the addition of Giemsa stain and could clearly be seen on the cell phone screen; the irregular crescent moon–shaped sickle cells were easy to spot, as well.
Testing for tuberculosis was trickier. Currently, the best method is to stain cells with a dye that will fluoresce when the pathogen is present and use a fluorescent microscope—a variation of the light microscope— to see the glow. Such microscopes, however, cost tens of thousands of dollars.
While developing the CellScope, Brelauer's group noticed that blue light-emitting diodes provide enough light to trigger this fluorescence. The discovery, he says, "was somewhat serendipitous. It so happened that we were working on this at the same time that LED technology started becoming affordable." The researchers added blue LEDs to the adapter, at a cost of about $10 each, and each diode lasts about 50,000 hours, according to Breslauer. The group even had room to add filters, which are used in fluorescent microscopes to block extraneous light from contaminating the image.