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Wide-spread screening of foods for toxins requires new technologies that are easily deployed and can quickly analyze many samples. We propose to implement immunoassays, assembled on the surface of luminescent/magnetic nanoparticles, to provide wide-spread screening for Staphylococcus enterotoxins and Shiga/Shiga-like toxin in foods. We will make use of nanoscale materials that are multifunctional, with both magnetic and luminescent properties and use the novel properties of these materials to improve the kinetics and the sensitivity of our assays. Superparamagnetic iron oxide particles can be heated by a high frequency external magnetic field that surrounds our assay without the feed-throughs that would be necessary with resistance heaters. Increasing the temperature of the assay is expected to improve the kinetics significantly. Furthermore, we will use gold shell/lanthanide oxide composite particles as primary particles on which capture antibodies are immobilized to explore the use of a fast, pulsed laser to provide a measure of the proximity of secondary antibody labels to the surface of the primary particles. The diffusion of energy from the primary particle will change the emission characteristics of temperature-sensitive secondary labels, and will enable us to determine whether secondary labels are specifically bound in the proximity of our antibodies, or are in solution distant from the primary particles. This technique may permit wash-free assays, which will significantly speed up the process and reduce the number of reagents and steps. Such rapid, simple assays will result in a greater ability to screen foods for toxins thus protecting the food supply and human health.
NON-TECHNICAL SUMMARY: Wide-spread screening of foods for toxins requires new technologies that are easily deployed and can quickly analyze many samples. We propose to implement immunoassays, assembled on the surface of luminescent/magnetic nanoparticles, to provide wide-spread screening for Staphylococcus enterotoxins and Shiga/Shiga-like toxin in foods. We will make use of nanoscale materials that are multifunctional, with both magnetic and luminescent properties and use the novel properties of these materials to improve the kinetics and the sensitivity of our assays. The techniques that will be developed as part of this research will significantly speed up the process and reduce the number of reagents and steps. Such rapid, simple assays will result in a greater ability to widely screen foods for toxins, thus protecting the food supply and human health.
<P>APPROACH: The project aims to develop the detection of SE and Shiga toxins with nanoparticle immunosensors. The demonstration of nanotechnology with conventional laboratory instrumentation such as microplate readers is the first step towards the development of a useful, portable, and automated measurement system. Initially the multiplexed MLNP-based immunoassays for SE and Shiga toxins will be developed in a conventional format that will be expanded later to a microcapillary system. The nanoparticle-based assay in the microcapillary format will be extended to multiplexed toxin analysis. Following optimization in buffer solution, we shall apply the nanoparticle-based immunosensor to real food samples. The validation of the immunosensor to real foods and sample preparation studies will be performed based on our experience on the immunoanalysis of a variety of contaminants in food. The kinetics of the assay will be improved with magnetic field heating of superparamagnetic iron oxide nanoparticles. Magnetite (Fe3O4) particles with a mean diameter of about 18 nm will be synthesized by the method of co-precipitation. A model assay for human IgG will be performed in the micro-capillary system. We will modify this system to include a coil wrapped around the capillary to produce a magnetic field for heating the nanoparticles in the sample. Pulsed laser heating of gold shell - lanthanide core nanoparticles will be investigated. This will require the synthesis of gold-lanthanide core-shell particles that will be deployed in a pulsed heating scheme with immunoassays. We plan to use the thermal pulse from a heated nanoparticle as a marker of proximity and specific binding in our assays. The results of our research will be presented at national meetings such as the ACS National Meeting. Manuscripts describing our work will be submitted to major scientific journals. Undergraduate students will offered the opportunity to participate in our work.