Portable sample processing for molecular assays: application to Zika virus diagnostics

Lab Chip. 2022 May 3;22(9):1748-1763. doi: 10.1039/d1lc01068a.

Abstract

This paper introduces a digital microfluidic (DMF) platform for portable, automated, and integrated Zika viral RNA extraction and amplification. The platform features reconfigurable DMF cartridges offering a closed, humidified environment for sample processing at elevated temperatures, as well as programmable control instrumentation with a novel thermal cycling unit regulated using a proportional integral derivative (PID) feedback loop. The system operates on 12 V DC power, which can be supplied by rechargeable battery packs for remote testing. The DMF system was optimized for an RNA processing pipeline consisting of the following steps: 1) magnetic-bead based RNA extraction from lysed plasma samples, 2) RNA clean-up, and 3) integrated, isothermal amplification of Zika RNA. The DMF pipeline was coupled to a paper-based, colorimetric cell-free protein expression assay for amplified Zika RNA mediated by toehold switch-based sensors. Blinded laboratory evaluation of Zika RNA spiked in human plasma yielded a sensitivity and specificity of 100% and 75% respectively. The platform was then transported to Recife, Brazil for evaluation with infectious Zika viruses, which were detected at the 100 PFU mL-1 level from a 5 μL sample (equivalent to an RT-qPCR cycle threshold value of 32.0), demonstrating its potential as a sample processing platform for miniaturized diagnostic testing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Humans
  • Molecular Diagnostic Techniques
  • Nucleic Acid Amplification Techniques
  • RNA
  • RNA, Viral / analysis
  • RNA, Viral / genetics
  • Real-Time Polymerase Chain Reaction
  • Sensitivity and Specificity
  • Specimen Handling
  • Zika Virus Infection* / diagnosis
  • Zika Virus* / genetics

Substances

  • RNA, Viral
  • RNA

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