Editors' ChoicePoint-of-Care Diagnostics

Blue-CHIP Diagnostics

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Science Translational Medicine  24 Aug 2011:
Vol. 3, Issue 97, pp. 97ec136
DOI: 10.1126/scitranslmed.3003049

With the ongoing centralization of medical and laboratory services in resource-poor settings, there remains an urgent need to develop easy-to-use point-of-care (POC) diagnostics. In these settings, POC diagnostics provide timely options for diagnosis, counseling, and treatment. By integrating clever microfluidic device manufacturing, fluid handling, and signal detection, Chin and colleagues demonstrate the successful application of a POC diagnostic assay, called mobile microfluidic chip for immunoassay on protein markers (mCHIP), for diagnosing HIV and syphilis—two common sexually transmitted diseases in that remote setting known to be underdiagnosed in antenatal care cases.

Chin et al. focused on a technical challenge of integrating multiple benchtop immunoassay steps into their mCHIP in a cost-effective manner. To minimize cost, they used injection molding of hard plastic components, a technique that is amenable to mass production. Next, they optimized fluid handling and signal output. A “bubble-based” method of reagent delivery was used to separate their delivery spatiotemporally. By displacing a certain amount of air in a syringe, precise volumes of reagents separated by air bubbles were drawn into the microfluidic cassette (an electricity-free process). To amplify the output signal in the mCHIP, the authors used a technique that plates silver onto gold nanoparticles. The optical density of the silver film was then quantified using a photodetector. This approach allowed for rapid turnaround (5 min to signal) and lower limits of pathogen detection—all with the use of low-cost photodetectors.

To ensure real-world applicability in the detection of HIV and syphilis, Chin et al. tested their POC mCHIP device in Rwanda. Using as little as 1 µl of unprocessed whole blood in the field, they could identify 100% (42/42) of HIV-positive persons and 96% (27/28) of persons known to be HIV-negative, in less than 15 min. When tested on commercial sex workers in Kigali, Rwanda, the POC mCHIP showed excellent performance characteristics as a combined HIV-syphilis diagnostic test. Although the authors demonstrated immediate POC application of mCHIP in remote clinics in developing countries, this cost-effective technology may also be extended to other high-burden infectious diseases in remote settings around the world.

C. D. Chin et al., Microfluidics-based diagnostics of infectious diseases in the developing world. Nat. Med. 17, 1015–1019 (2011). [Abstract]

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