Highly Monodisperse Fe3O4@Au Superparamagnetic Nanoparticles as Reproducible Platform for Genosensing Genetically Modified Organisms

Several routes have been developed to prepare magnetic core–shell Fe3O4@Au nanoparticles (MNPs). However, only highly monodisperse MNPs are suitable for analytical applications. Herein, we describe the detection of GMO through the use of gold-coated MNPs with fine-tuned properties as platforms. The MNPs were prepared through a procedure that involves the preparation of Fe3O4 cores by thermal decomposition and their coating through reduction of a gold precursor. Different Fe3O4:Au precursor molar ratios (1:1; 1:4; 1:7) were tested on the Fe3O4 encapsulation. Monodisperse quasi-spherical core–shell Fe3O4@Au were obtained for the 1:4 and 1:7 ratios, in contrast, the 1:1 ratio did not lead to complete encapsulation of Fe3O4 cores. Therefore, the Fe3O4@Au obtained from higher Fe3O4:HAuCl4 ratios were tested as platforms for an electrochemical genoassay to detect MON810. The best performance was achieved with the Fe3O4@Au prepared from 1:4 ratio (10.0 ± 1.7 nm). A DNA probe covalently linked to a carboxylated self-assembled monolayer and a fluorescein isothiocyanate (FITC) signaling probe were used in a sandwich assay format. Labeling with anti-FITC-peroxidase Fab fragment conjugate allowed chronoamperometric measurements of the enzyme activity captured on Fe3O4@Au placed on screen-printed electrodes upon the hybridization event. The genoassay provided a linear range from 0.25 to 2.5 nM, LOD of 0.15 nM, with a reproducibility <4%. Certified samples containing the transgenic event were measured without further purification after PCR amplification. The results highlight the efficiency of the genoassay for the MON810 detection, opening new horizons to achieve a low-cost analysis out of large laboratory facilities to verify the compliance of GMO regulations.