Method Preserves Microfluidic Devices for HIV Monitoring in Developing Countries

A novel method has been developed to store microfluidic devices for CD4 T cell testing in extreme weather conditions for up to six months without refrigeration.

Bioengineers at Stanford University School of Medicine (Palo Alto, CA, USA) and their colleagues employed a lensless imaging method to rapidly count CD4 T cells using complementary metal-oxide semiconductor (CMOS) sensor, the same imaging sensor found in cell phone cameras. Lensless imaging technology allows rapid cell counting and does not require skilled technicians to operate, making it suitable for point-of-care settings. If produced at a large scale, the microfluidic device would cost less than USD 1 compared with the current cost of a CD4 assay, which is about USD 30–50.

The investigators used trehalose, a form of sugar that is present in some plants and animals, to preserve the microfluidic device. Since trehalose has the capability to enable plants to thrive in very harsh hot and cold conditions, they determined that it could have the same effect on multilayer surfaces like a microfluidic device. They packaged and vacuum-sealed the trehalose treated device in plastic and used a drying agent to address the effects of humidity. They exposed the device to extreme weather conditions in a laboratory environment to test its functionality and shelf life.

The results of the study revealed that they were able to preserve the microfluidic devices over a period of six months using this method. At room temperature, they observed 90% specificity for up to six months. The engineers also integrated these stabilized microfluidic devices post-reactivation with the CMOS lensless imaging technology. The captured CD4 T cells were counted rapidly and automatically from unprocessed whole blood, creating a portable, battery-operated, inexpensive, and microscope-free CD4 T cell counting platform with a long shelf life.

Waseem Asghar, PhD, an assistant professor of electrical engineering and co-first author of the study, said, “Monitoring HIV patients at point-of-care settings in resource-constrained countries like Africa are critical in knowing how their treatment is progressing and whether or not a particular drug is working the way it should.” The study was originally published online on February 17, 2016, in the journal Scientific Reports.

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Stanford University School of Medicine