In a twist on traditional smart-phone accessories, researchers have demonstrated fluorescent microscopy using a physical attachment to an ordinary cell phone. The researchers behind the device say that it could identify and track diseases like tuberculosis (TB) and malaria in developing countries with limited access to health care, or in rural areas of the U.S.

The "Cellscope," which came out of an optics-class project at the University of California, Berkeley, could capture and perform simple analysis of magnified images of blood and sputum samples, or transmit the images over the cell-phone network for analysis elsewhere.

The contraption--a tube-like extension hooked onto the cell phone with a modified belt clip--works just like a traditional microscope, using a series of lenses that magnify blood or spit samples on a microscope slide. To detect TB, for example, a spit sample is infused with an inexpensive dye called auramine. An "excitation" wavelength is emitted by the light source--a blue light-emitting diode (LED) on the opposite end of the device from the cell phone--and absorbed by the auramine dye in the spit sample, which fluoresces green to illuminate TB bacteria. Then automated software can count the green bacteria for a diagnosis in real time, or the image can be transmitted via cell network to a separate facility where doctors can analyze it and respond.

"The cell phone approach is very valuable for all parts of the world where [medical] resources are scarce," says Aydogan Ozcan, an assistant professor of electrical engineering at UCLA, who is working to develop a lens-free method for mobile cell imaging. "It's a great step forward in this important area."

The researchers involved with the project, led by Berkeley bioengineering professor Daniel Fletcher, describe their work in a paper published in the journal PLoS One. They previously demonstrated a prototype device that used white light, or bright-field imaging, to capture magnified images of blood cells stained to detect malaria parasites, an approach that could also identify the oddly shaped red blood cells indicating sickle cell disease. Fluorescence adds a new capability that could be particularly useful if made cheaper and portable.

"Fluorescence microscopy in resource-poor countries is hard," says Wilbur Lam, a bioengineer and physician in the UCSF School of Medicine who worked on the project as a clinical expert. "Lab-grade [fluorescence] technology is expensive and hard to operate," he says. "You need a dark room, a mercury lamp, and a lot of training." These facilities aren't available in many areas of developing nations, which, Lam notes, are the places that most need the technology to detect common diseases like TB. The Cellscope device could be distributed to health workers in remote areas, extending the reach of fluorescence-based medical imaging.