Since foodborne diseases have become one of the major threats to human health, food safety has increased public concern around the world. Staphylococcal enterotoxins are one of the most common causes of acute food contamination and poisoning, accounting for numerous foodborne-disease outbreaks all over the world. To ensure a fast surveillance and response to foodborne-disease outbreaks, a rapid analytical method is required which enables a sensitive quantification of SEB in complex food matrices.
Magnetic nanocomposites offer the major advantage of being easily separated from complex food matrices and are thus perfectly suitable for immunomagnetic enrichment procedures. The ultimate goal of this thesis was the coupling of a facile and efficient immunomagnetic separation (IMS) step based on nanocomposites with specifically tailored magnetic and morphological characteristics to a sensitive microarray analysis on the automated flow-based microarray analysis platform MCR 3. Hereby, the potential of a prior selective pre-enrichment and concentration step by IMS to increase the assay sensitivity and enable the possibility to rapidly analyze larger amounts of food samples was tested.
An important task during the PhD thesis was the synthesis of iron oxide-shell silica core nanocomposites which bear highly beneficial magnetic features for applications in IMS - the simple manipulation by permanent magnets and superparamagnetism for easily switching on and off the magnetic response.
For the first time, the novel iron oxide-shell silica-core nanocomposites were applied along with antibodies against SEB to establish a highly sensitive magnetic nanocomposite-based sandwich microarray immunoassay (MNC-SMIA) on the microarray platform MCR 3 SLT. To realize this immunoassay, iron oxide-shell silica-core nanocomposites functionalized with biotinylated anti-SEB detection antibodies were incubated in milk spiked with SEB. Nanocomposites bind SEB in the milk by an affinity reaction. An IMS step was applied, to selectively enrich and isolate SEB from the initial sample volume of either 0.6 mL or 100 mL.
In order to guarantee a rapid magnetic separation of the nanocomposites, both manual and automatic separation techniques were tested with regard to time-effectiveness, effectivity and practicability. SEB was quantified by MNC-SMIA. The assay readout is performed by chemiluminescence (CL) imaging after enzymatic reaction of horseradish peroxidase with luminol and hydrogen peroxide on each spot of the microarray.
The MNC-SMIA was eventually stepwise optimized. On the basis of our results, the application of the novel magnetic nanocomposites appeared to be a major improvement of the conventional CL-SMIA in food matrix. Enrichment procedures, even from large samples up to 100 mL, are now possible, resulting in a further improvement of sensitivity.
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Since foodborne diseases have become one of the major threats to human health, food safety has increased public concern around the world. Staphylococcal enterotoxins are one of the most common causes of acute food contamination and poisoning, accounting for numerous foodborne-disease outbreaks all over the world. To ensure a fast surveillance and response to foodborne-disease outbreaks, a rapid analytical method is required which enables a sensitive quantification of SEB in complex food matrices...
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