Nowadays luminescent semiconductor quantum dots (QDs) are widely applied in different areas due to their unique optical properties. QDs can be used as photoluminescent labels with excellent possibilities for high-throughput detection and diagnostics. For most of such applications QDs must be coupled to biomolecules, which often represents a fundamental challenge. Although QDs have a lot of advantages over organic dyes, most of the techniques that have been developed for QD functionalization and bioconjugation, are more complicated than the corresponding techniques for organic fluorescent dyes. Here, the importance of choosing a suitable bioconjugation strategy in different applications, such as imaging and assays is described. The main goal of this review is to give a structured and detailed overview and comparison of the most widely used conjugation strategies in function of the active groups (carboxyl, amine, thiol, epoxy, hydroxyl and aldehyde groups) present on QD surface.

A multiplex lateral flow immunoassay (LFIA) for the determination of the mycotoxins deoxynivalenol, zearalenone, and T2/HT2-toxin in barley was developed with luminescent quantum dots (QDs) as label. The synthesized QDs were hydrophilized by two strategies, that is, coating with an amphiphilic polymer or silica. The water-soluble QDs were compared with regard to their bioconjugation with monoclonal antibody (mAb) and were tested on a LFIA. Silica-coated QDs that contained epoxy groups were most promising. Therefore, green, orange, and red epoxy-functionalized silica-coated QDs were conjugated with anti-ZEN, anti-DON, and anti-T2 mAb, respectively. The LFIA was developed in accordance with the European Commission legal limits with cutoff limits of 1000, 80, and 80 μg/kg for deoxynivalenol, zearalenone, and T2/HT2-toxin, respectively. The LFIA gave a fast result (15 min) with a low false-negative rate (<5%), and the results were easy to interpret without any sophisticated equipment.

Bacterial toxins are food safety hazards causing about 10% of all reported foodborne outbreaks in Europe. Pertinent to Gram‐positive pathogens, the most relevant toxins are emetic toxin and diarrheal enterotoxins of Bacillus cereus, neurotoxins of Clostridium botulinum, enterotoxin of Clostridium perfringens, and a family of enterotoxins produced by Staphylococcus aureus and some other staphylococci. These toxins are the most important virulence factors of respective foodborne pathogens and a primary cause of the related foodborne diseases. They are proteins or peptides that differ from each other in their size, structure, toxicity, toxicological end points, solubility, and stability, types of food matrix to which they are mostly related to. These differences influence the characteristics of required detection methods. Therefore, detection of these toxins in food samples, or detection of toxin production capacity in the bacterial isolate, remains one of the cornerstones of microbial food analysis and an essential tool in understanding the relevant properties of these toxins. Advanced research has led into new insights of the incidence of toxins, mechanisms of their production, their physicochemical properties, and their toxicological mode of action and dose‐response profile. This review focuses on biological, immunological, mass spectrometry, and molecular assays as the most commonly used detection and quantification methods for toxins of B. cereus, C. botulinum, C. perfringens, and S. aureus. Gathered and analyzed information provides a comprehensive blueprint of the existing knowledge on the principles of these assays, their application in food safety, limits of detection and quantification, matrices in which they are applicable, and type of information they provide to the user.

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