Bio–barcode triggered isothermal amplification in a fluorometric competitive immunoassay for the phytotoxin abrin


Abrin is one of the most toxic phytotoxins to date, and is a potential biological warfare agent. A bio–barcode triggered isothermal amplification for fluorometric determination of abrin is described. Free abrin competes with abrin–coated magnetic microparticles (MMP) probes to bind to gold nanoparticle (AuNP) probes modified with abrin antibody and bio–barcoded DNA. Abundant barcodes are released from the MMP–AuNP complex via dithiothreitol treatment. This triggers an exponential amplification reaction (EXPAR) that is monitored by real–time fluorometry, at typical excitation/emission wavelengths of 495/520 nm. The EXPAR assay is easily operated, highly sensitive and specific. It was used to quantify abrin in spiked commercial samples. The detection limit (at S/N = 3; for n = 6) is 5.6 pg·mL−1 which is considerably lower than previous reports. This assay provides a universal sensing platform and has great potential for determination of various analytes, including small molecules, proteins, DNA, and cells.

Schematic representation of the bio–barcode triggered exponential amplification reaction (EXPAR) for a fluorometric competitive immunoassay for abrin. The limit of detection is 5.6 pg mL−1 with a large dynamic range from 10 pg mL−1 to 1 µg mL−1.

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This work was supported by the National Key Research and Development Program of China (No. 2017YFC1200903), the Key Research and Development Program of Tianjin (No. 18YFZCNC01260).

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Correspondence to Zhixian Gao or Yonggang Hu.

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Sun, X., Fei, R., Zhang, L. et al. Bio–barcode triggered isothermal amplification in a fluorometric competitive immunoassay for the phytotoxin abrin. Microchim Acta 187, 127 (2020).

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  • Bio–barcode DNA
  • Exponential amplification reaction
  • Gold nanoparticles
  • Magnetic microparticles
  • Antibody
  • Immunoreaction
  • Real–time fluorometry