Weighing about half an ounce, costing less than $5, and able to attach to a cell phone, an optofluidic platform that integrates flow cytometry and fluorescent microscopy can be used to rapidly image bodily fluids for cell counts or cell analysis.
Details of the work, conducted at the BioPhotonics Laboratory at the UCLA Henry Samueli School of Engineering and Applied Science (Los Angeles, CA), are currently available online in the journal Analytical Chemistry. Led by by Aydogan Ozcan, a professor of electrical engineering and bioengineering and a member of the California NanoSystems Institute at UCLA, the team integrated compact optical attachments to create the optofluidic fluorescent cytometry platform, which includes one simple lens costing less than $3, one plastic color filter (less than $1), two LEDs (less than 30 cents each), and simple batteries.
The microfluidic assembly is placed just above a separate, inexpensive lens that is put in contact with the cell phone's existing camera unit, allowing the entire cross-section of the microfluidic device to be mapped onto the phone's CMOS sensor-chip. The sample fluid is delivered continuously through a disposable microfluidic channel via a syringe pump.
The device is illuminated from the side by the LEDs using a simple butt-coupling technique. The excitation light is then guided within the cross-section of the device, uniformly exciting the specimens in the imaging fluid. The optofluidic pumping scheme also allows for the use of an inexpensive plastic absorption filter to create the dark-field background needed for fluorescent imaging.
In addition, video post-processing and contour-detection and tracking algorithms are used to count and label the cells or particles passing through the microfluidic chip.
In order to demonstrate proof-of-concept for the new platform, the team used the device to measure the density of white blood cells in human whole-blood samples, as white blood cell density is routinely tested to diagnosis various diseases and infections, including leukemia, HIV and bone marrow deficiencies.
Next steps for the device include other potential applications such as counting potential waterborne parasites for water-quality monitoring, says Hongying Zhu, a UCLA Engineering postdoctoral scholar at the BioPhotonics Lab and co-author of the research. Ozcan adds that deployment and testing of the device in extremely poor-resource countries—where the device would be best useful due to its low cost—is likely as well.
The National Institutes of Health, the National Science Foundation, the Office of Naval Research, the Gates Foundation and the Vodafone Americas Foundation all supported this work.