Diagnostic Chips for Global Health

Assistant Professor Samuel K. Sia of the Department of Biomedical Engineering is developing new portable medical diagnostic devices for use in developing countries, such as those in sub-Saharan Africa, based on "lab-on-a-chip" technology originating from the microelectronics industry. This device is a hand-held instrument that will show when HIV patients are in danger of developing AIDS, thereby providing physicians in developing countries with an inexpensive and immediate way to diagnose the progression of AIDS in order to start antiretroviral medications.

One known characteristic that marks the transition from HIV to AIDS is the continual reduction in the number of CD4+ lymphocytes. In Professor Sia's device, a patient's blood sample is taken using a 
Professor Sia's research team includes, photo on the left, l. to r., undergraduate Ben Lee '10 and Ph.D. student Yukkee Cheung, with Professor Sia (standing), and, in photo right, Ph.D. student Curtis Chin.

simple finger prick (similar to diabetic patients using glucose meters), and the blood is routed through a series of tiny channels inside a credit card-sized chip where CD4+ lymphocytes are captured. A handheld instrument that is battery-operated and low-cost (consisting of laser-emitting diodes, photodetectors, a micropump, and electronics on a printed circuit board) will read the number of CD4+ lymphocytes present in the blood.
 
Once the progression from HIV to AIDS has been discovered, patients can be immediately started on an antiretroviral regimen that may prolong their life significantly. An additional benefit of having this low-cost test that monitors the CD4+ level is that it becomes an important diagnostic tool to monitor cases of drug resistance.
 
"Designing diagnostic instruments for use in resource-poor settings is a tremendous engineering challenge but at the same time offers clearly tangible clinical benefit," says Sia. "Not only does the device have to work accurately and robustly, it also has to be simple to use and tremendously affordable. Over the last few years, we have re-designed many aspects of microfluidics, a technology that has the potential to move the bulk of lab-based diagnostic tests towards portable testing, towards fulfilling this goal. For this CD4 counting project, instead of flow cytometry that uses advanced lasers and optics, we have simplified the fluid handling and optical detection to the point where it is feasible to imagine making this important clinical determination in remote locations."
 
Professor Sia's research is supported in part by the Walter C. Coulter Foundation, which has recently awarded him a Phase II award for his grant proposal, BioMEMS Device for counting CD4+ Lymphocytes. His clinical collaborators on this project include Dr. Jessica Justman and Dr. Wafaa El-Sadr at the Mailman School of Public Health.
 
"We have tried to integrate considerations of the clinical environments throughout our whole design process," says Sia. "We are pleased to work with Drs. El-Sadr and Justman, who have set up a tremendous network of sites in Africa where we can test our device. Phase II of the Coulter Foundation Award will allow us to test our devices in sub-Saharan Africa, in countries such as Rwanda, where we can closely assess the sensitivity, specificity, and predictive values of these tests."
 
This CD4 project builds on Sia's previous translational research in bringing microfabricated devices to resource-poor settings. Recently, his work on global health diagnostics has also received grants from the NIH and the World Health Organization. In addition, since a low-cost and portable medical diagnostics device is also important for "point-of-care" testing in the U.S., his work has led to the founding of a venture capital-backed startup company, Claros Diagnostics, located in Woburn, MA, which he co-founded with two colleagues and which focuses on developing a prostate cancer test for physicians' offices.
 
Sia continues, "There are important differences between designing devices for sub-Saharan Africa versus the U.S., but perhaps even more commonalities. A cheap, simple-to-use, handheld diagnostic device is useful in many clinical settings. Working in developing countries has a special place in our hearts because the engineering challenge is so great, and the clinical value so immediate and rewarding."

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