Detection of ricin toxin in water using immunoassays

Abstract

Two types of immunoassays were employed to determine ricin toxin through the substitute of A chain sub-unit in water. Protocol for detecting ricin by commercial enzyme-linked immunosorbent assay (ELISA) kits was established and evaluated. Final results were obtained by this assay in six hours and the detection limit was found to be less than 3 ng mL⁻¹ based on ricin A chain. Cross-reactivity from ricin B chain was minimal. The validated assay was successfully applied to the determination of ricin toxin in water for the purpose of water security. The results showed that water samples were free from this biotoxin. In order to reduce the assay time and enhance the ability of securing water quality, a fibre optic biosensor RAPTOR™ has been applied as another platform to rapidly analyse ricin toxin in water. Polyclonal anti-ricin antibody was captured on the waveguide through incubation. Four waveguides were assembled into each coupon, which could provide multiplex analysis in one assay run. Cy5-labelled antibody was used as detector antibody and characterised by MALDI-TOF mass spectrometry. Results showed that the detection limit was 10 and 60 ng mL⁻¹ of ricin A chain in deionised water and tap water, respectively. Based on readily assembled coupon, the assay run could be completed and the results reported in less than 15 minutes. Thus, the biosensor has been shown to be a promising technology for rapid and sensitive detection of biotoxins in water. In the future, more research work will be carried out to further improve the sensitivity and enhance reproducibility of the assay for the detection of ricin toxin.

Keywords:

• ricin toxin
• ricin A chain
• immunoassay
• ELISA
• biosensor
• antibody
• MALDI-TOF mass spectrometry

Acknowledgement

The authors would like to thank Dr. Guo Zhongxian for the assistance in characterising antibodies by MALDI-TOF MS technique.