Catalytic ferromagnetic gold nanoparticle immunoassay for the detection and differentiation of Mycobacterium tuberculosis and Mycobacterium bovis

Linda Stewart, Cuong Cao, Brendan Gilbride, Michael Hust, Gustavo Moreira

Research output: Contribution to journalArticlepeer-review

Abstract

A ferromagnetic gold nanoparticle based immune detection assay, exploiting the enhanced signal amplification of inorganic nanozymes, was developed and evaluated for its potential application for the detection of Mycobacterium tuberculosis complex (MTBC) organisms, and simultaneous identification of Mycobacterium bovis. Ferromagnetic gold nanoparticles (Au-Fe3O4 NPs) were prepared by combining sodium citrate capped gold and co-precipitated Fe3O4 NPs, in solution. Au-Fe3O4 NPs possess intrinsic peroxidase-like activity and can catalyse conventional peroxidase substrates including 3,3’,5’,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). When the Au-Fe3O4 NPs were functionalised by direct coupling with MTBC-specific antibodies, a nanoparticle based immune detection assay (NPIDA) was developed which could detect Mycobacterium tuberculosis (MTB) and differentiate M. bovis. The intrinsic magnetic capability of the Au-Fe3O4 NPs was exploited in sample preparation and the functionalised Au-Fe3O4 NPs were used to capture target bacterial cells from the sample. These were then incorporated into a novel immunoassay which included a second recombinant monoclonal antibody (mAb) as detector. The formation of a blue TMB oxidation product, with a peak absorbance of 370 nm, indicated successful capture and identification of the target. The detection limit of the NPIDA was found to be 1 x 103 CFU mL-1 for both MTB and M. bovis. This is tenfold more sensitive when compared to conventional ELISA format using the same antibodies, and no matrix effects were observed in either assay.
This novel NPIDA was capable of simultaneous sample concentration, purification, and immunological sensing and detection. To our knowledge, it represents the first immune-based diagnostic capable of identifying MTBC organisms and simultaneously differentiating M. bovis.
Original languageEnglish
JournalAnalytica Chimica Acta
Publication statusAccepted - 07 Aug 2021

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