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Biomedical Microdevices

, 21:24 | Cite as

Immuno-gold silver staining assays on capillary-driven microfluidics for the detection of malaria antigens

  • Ngoc M. Pham
  • Sebastian Rusch
  • Yuksel Temiz
  • Hans-Peter Beck
  • Walter Karlen
  • Emmanuel DelamarcheEmail author
Article

Abstract

Accurate and affordable rapid diagnostic tests (RDTs) are indispensable but often lacking for many infectious diseases. Specifically, there is a lack of highly sensitive malaria RDTs that can detect low antigen concentration at the onset of infection. Here, we present a strategy to improve the sensitivity of malaria RDTs by using capillary-driven microfluidic chips and combining sandwich immunoassays with electroless silver staining. We used 5 μm fluorescent beads functionalized with capture antibodies (cAbs). These beads are self-assembled by capillary action in recessed “bead lanes”, which cross the main flow path of chips microfabricated in Si and SU-8. The binding of analytes to detection antibodies (dAbs) and secondary antibodies (2ndAbs) conjugated to gold nanoparticles (NPs) allows the formation of a silver film on the beads. Such silver film masks the fluorescent core of the bead inversely proportional to the concentration of antigen in a sample. We illustrate this method using the recombinant malaria antigen Plasmodium falciparum histidine-rich-protein 2 (rPfHRP2) spiked in human serum. This antigen was a recombinant HRP2 protein expressed in Escherichia coli, which is also the standard reference material. The limit of detection (LOD) of our immunoassay was found to be less than 6 ng mL−1 of rPfHRP2 within 20 min, which is approaching the desired sensitivity needed in the Target Product Profile (TPP) for malaria elimination settings. The concept presented here is flexible and may also be utilized for implementing fluorescence immunoassays for the parallel detection of biomarkers on capillary-driven microfluidic chips.

Keywords

Malaria infection PfHRP2 Fluorescent beads Capillary Microfluidics Silver staining immunoassays 

Notes

Acknowledgements

Ngoc M. Pham received an Engineering for Development Scholarship from ETH Global and the Sawiris Foundation for Social Development. Walter Karlen is supported through the Swiss National Science Foundation professorship award 150640 “Intelligent point-of-care monitoring”. Yuksel Temiz and Emmanuel Delamarche thank Elisa Hemmig, Robert Lovchik and Onur Gökçe for discussions and Walter Riess and the IBM Research Frontiers Institute for their continuous support.

Compliance with ethical standards

Conflict of interest

None

Supplementary material

10544_2019_376_MOESM1_ESM.docx (834 kb)
ESM 1 (DOCX 833 kb)

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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.ETH Zürich, Mobile Health Systems Lab, Department of Health Sciences and Technology, BAAInstitute of Robotics and Intelligent SystemsZürichSwitzerland
  2. 2.Swiss Tropical and Public Health InstituteBaselSwitzerland
  3. 3.University of BaselBaselSwitzerland
  4. 4.Kantonsspital Aarau AG, Medizinische GenetikInstitut für LabormedizinAarauSwitzerland
  5. 5.IBM Research – ZurichRüschlikonSwitzerland

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