Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 116, Issue 10, Pages 4489-4495Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1814110116
Keywords
digital; ELISA; portable; multiplex; cell phone
Categories
Funding
- Department of Bioengineering, University of Pennsylvania
- National Institutes of Health Awards [1R33CA206907, 5R21CA182336]
- Hartwell Foundation
- Pennsylvania Consortium on Traumatic Brain Injury
- American Cancer Society CEOs Against Cancer CA Division Research Scholar Grant [RSG-15-227-01-CSM]
- National Science Foundation CAREER Award [1554200]
- Microsoft Graduate Fellowship
- Div Of Chem, Bioeng, Env, & Transp Sys
- Directorate For Engineering [1554200] Funding Source: National Science Foundation
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Digital droplet assays-in which biological samples are compartmentalized into millions of femtoliter-volume droplets and interrogated individually-have generated enormous enthusiasm for their ability to detect biomarkers with single-molecule sensitivity. These assays have untapped potential for point-of-care diagnostics but are currently mainly confined to laboratory settings, due to the instrumentation necessary to serially generate, control, and measure tens of millions of droplets/compartments. To address this challenge, we developed an optofluidic platform that miniaturizes digital assays into a mobile format by parallelizing their operation. This technology is based on three key innovations: (i) the integration and parallel operation of a hundred droplet generators onto a single chip that operates > 100 x faster than a single droplet generator, (ii) the fluorescence detection of droplets at > 100 x faster than conventional in-flow detection using time domain-encoded mobile phone imaging, and (iii) the integration of on-chip delay lines and sample processing to allow serum-to-answer device operation. To demonstrate the power of this approach, we performed a duplex digital ELISA. We characterized the performance of this assay by first using spiked recombinant proteins in a complex media (FBS) and measured a limit of detection, 0.004 pg/mL (300 aM), a 1,000 x improvement over standard ELISA and matching that of the existing laboratory-based gold standard digital ELISA system. We additionally measured endogenous GM-CSF and IL6 in human serum from n = 14 human subjects using our mobile duplex assay, and showed excellent agreement with the gold standard system (R-2 = 0.96).
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