Executive Summary
Johns Hopkins University researchers are testing a low-cost diagnostic tool that detects chlamydia within 30 minutes. The tool, tentatively called mobiLab, is made of a disposable cartridge for a genital swab sample and a heating unit that incubates the DNA to facilitate a reaction. The test results are delivered to and processed by a mobile app on a smartphone connected to the battery-powered device.
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The battery-powered device, the size of a coffee mug, works by using a microfluidics cartridge to detect the DNA of chlamydia bacteria in genital swab samples. The DNA analysis unit is integrated with a smartphone, which enables the user to control the platform and process test data with a smartphone app.
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The testing device costs about $200 to manufacture. Developers estimate the per-run cost of the platform at $2.
Researchers at Baltimore-based Johns Hopkins University (JHU) are testing a low-cost diagnostic tool that detects chlamydia within 30 minutes. The tool, tentatively called mobiLab, is made of a disposable cartridge for a genital swab sample and a heating unit that incubates the DNA to facilitate a reaction. The test results are delivered to and processed by a mobile app on a smartphone connected to the battery-powered device.1
National data indicate that an estimated 1.8 million Americans ages 14-39 are infected with chlamydia, with rates of infection highest among young women. An estimated 4.7% of women ages 14-24 were infected with the disease in 2012, data suggest.2 (Contraceptive Technology Update’s “STI Quarterly” supplement reported on the data. See “Nearly 5% of young U.S. women have chlamydia,” December 2014.)
Since the beginning of the 21st century, healthcare providers have been able to expand chlamydia screening programs through development of nucleic acid amplification (NAAT) testing. However, NAAT testing is too complex to perform in point-of-care settings such as clinicians’ offices, health fairs, school clinics, or other sexual health outreach venues.
Johns Hopkins University researchers, led by Jeff Tza-Huei Wang, PhD, from JHU’s BioMEMS Lab, presented initial results of the first low-cost NAAT platform that can diagnose chlamydia at the point of care and that integrates sample preparation, DNA amplification, and data processing at the 2015 American Association for Clinical Chemistry Annual Meeting and Clinical Lab Expo in Atlanta. The battery-powered device, the size of a coffee mug, works by using a microfluidics cartridge to detect the DNA of chlamydia bacteria in genital swab samples. The DNA analysis unit is integrated with a smartphone, which enables the user to control the platform and process test data with a smartphone app.
The testing device weighs as much as two or three iPhones and costs about $200 to manufacture. Developers estimate the per-run cost of the platform at $2.
Researchers now have fairly accurate, sensitive, and specific molecular assays to detect very few numbers of organisms in biological samples, said Dong Jin Shin, BME, one of the abstract’s authors and a PhD student at Johns Hopkins. However, many of these technologies are confined to use in centralized lab settings.
“If we’re able to bring molecular diagnostic technology closer to the clinic and deliver accurate results to clinicians sooner, then we’ll be able to improve our standard of care for patients with chlamydia, while also saving costs,” said Shin in a press statement accompanying the abstract presentation.
How does it perform?
The JHU researchers designed the heart of the mobiLab technology using magnetic particles as a mobile solid phase for DNA capture and transport. This simplified fluidic processing to particle translocation on a robust and scalable cartridge. Process integration facilitated by Bluetooth-enabled microcontrollers enable full control of the instrument by the user with a smartphone application, the researchers state.1
The mobiLab platform consists of three discrete units:
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a droplet microfluidic cartridge;
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a battery-powered instrument for droplet manipulation and amplification;
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a smartphone for user interface, data acquisition, and processing.
The microfluidic cartridge design uses open-surface magnetofluidic manipulation to enable bioassays requiring multiple buffer exchanges to be performed without complex instruments. The instrument uses a microcontroller that controls the rotary bead manipulator, thermal incubation, and Bluetooth-based communication with the smartphone application. Each assay consumes about 10% of the battery capacity, which allows up to 10 assays to be performed consecutively without access to a power outlet.
Researchers designed a single-stream loop-mediated isothermal amplification (LAMP) assay to operate in tandem with the mobiLab platform. Within this assay, polyhistidine-coated magnetic particles capture DNA targets from sample lysate via electrostatic interaction. The affinity between particles and nucleic acids is maintained at acidic pH, which is reversed when particles enter the LAMP buffer. The basic pH of LAMP mixture is compatible with the elution conditions for nucleic acids, which enables seamless integration between DNA extraction and amplification.
To test the single-stream assay, researchers used plasmid targets and were able to capture and amplify 103 copies of gene targets. Specificity of the assay for Chlamydia trachomatis was tested, and the absence of cross-reactivity with human or other bacterial genomic DNA was verified. The mobiLab platform was validated by testing Chlamydia trachomatis infection from patient-collected vaginal swab samples.
Volunteers enrolled in an internet-based chlamydia screening program, where two sets of swabs were self-collected and mailed back to the JHU lab. One set of swabs was analyzed using the gold standard Gen-Probe AC2 CT assay (San Diego), while the second set was tested using the mobiLab platform. The two results were in agreement for 20 out of 20 samples after 30-minute incubation, which demonstrated that the droplet assay performance is comparable to the gold standard for the samples tested.1
At the present time, the mobiLab technology hasn’t been tested for infections other than chlamydia; however, Wang says it could be used to test for other DNA/RNA-based infections. Researchers will continue looking at alternate uses for the technology, as well as confirm its use for possible commercial development.
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Shin D, Athamanolap P, Chen L, et al. Clinical evaluation of mobiLab, a smartphone-enabled microfluidic NAAT platform for Chlamydia trachomatis screening. Presented at the 2015 American Association for Clinical Chemistry Annual Meeting and Clinical Lab Expo. Atlanta; July 2015.
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Torrone E, Papp J, Weinstock H. Prevalence of Chlamydia trachomatis genital infection among persons aged 14-39 years — United States, 2007-2012. MMWR 2014; 63(38):834-838.
