Liposomes loaded with water-soluble and water-insoluble quantum dots (QD) were for the first time applied as labels in different heterogeneous immunoassays for the determination of food contaminants, using mycotoxin zearalenone (ZEN) as a model. A great deal of work was devoted to the optimal choice of phospholipids for the liposomes preparation and to the factors which are important for the stability and size of obtained liposomes. Thin-film hydration and reverse-phase evaporation techniques were evaluated in terms of stability of the obtained liposomes and their efficiency for QD loading. Conjugation of liposomes with proteins and the influence of cross-linkers to the nonspecific interaction of the obtained liposomes with the surface of microtiter plates and cartridges were investigated and 3-(2-pyridyldithio)propionic acid N-hydroxysuccinimide ester was found as the optimal cross-linker. The limits of detection (LOD) for ZEN of fluorescence-labeled immunosorbent assays were 0.6 μg kg(-1), 0.08 μg kg(-1), and 0.02 μg kg(-1), using QD, liposomes loaded with water-soluble QD, and water-insoluble QD, respectively. Similarly, the developed qualitative on-site tests using the different QD labels and taking into account the EU maximum residues level for ZEN in unprocessed cereals showed cutoff levels of 100, 50, and 20 μg kg(-1).

In: TALANTA, 134, 120-125, 2015. To refer to or to cite this work, please use the citation to the published version:Beloglazova N., Goryacheva O., Speranskaya E., Aubert T., Shmelin P. , Kurbangaleev V., Goryacheva I.Y., De Saeger S. (2015). Silica-coated liposomes loaded with quantum dots as labels for multiplex fluorescent immunoassay. TALANTA, 134,[120][121][122][123][124][125] AbstractThis manuscript describes synthesis and followed application of silica-coated liposomes loaded with quantum dots as a perspective label for immunoaasay. The hollow spherical structure of liposomes makes them an attractive package material for encapsulation of multiple water-insoluble quantum dots and amplifying the analytical signal. Silica coverage ensures the stability of the loaded liposomes against fusion and internal leakage during storage, transporting, application and also provides groups for bioconugation. For the first time these nanostructures were employed for the sensitive multiplex immunochemical determination of two analytes. As a model system mycotoxins zearalenone and aflatoxin B1 were detected in cereals. For simplification of multiassay results' evaluation the silanized liposomed loaded with QDs of different colors were used. The IC 50 values for the simultaneous determination of zearalenone and aflatoxin B1 were 16.2 and 18 µg kg -1 for zearalenone and 2.2 and 2.6 µg kg -1 for aflatoxin B1 in wheat and maize, respectively. As confirmatory method, liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used.

A quantitative fluorescence labeled immunosorbent assay (FLISA) and qualitative onsite column tests were developed for the determination of aflatoxin M1 (AfM1) in milk products. The use of quantum dots (QD) loaded liposomes as a label significantly increased the assay sensitivity by encapsulating multiple QD in a single liposome and, therefore, amplifying the analytical signal.Two different techniques were compared to obtain aflatoxin-protein conjugates, used for further coupling with the liposomes. The influence of non-specific interactions of the obtained liposomes-labeled conjugates with the surface of microtiter plates and column cartridges was evaluated and discussed. The limit of detection for FLISA was 0.014 µg kg -1 .For qualitative on-site tests the cut-off was set at 0.05 µg kg -1 taking into account the EU maximum level for aflatoxin M1 in raw milk, heat-treated milk and milk for the manufacture of milk based product. The direct addition of labeled conjugate in the milk samples resulted in an additional decrease of analysis time.An intra-laboratory validation was performed with sterilized milk and cream samples artificially spiked with AfM1 at concentrations less, equal and more than the cut-off level. It was shown that milk products could be analyzed without any sample preparation, just diluted with the buffer. The rates for false positive and false negative results were below 5% (2.6% and 3.3%, respectively).

No abstract

No abstract

The structural dependence of silica–liposome hybrids on silanization conditions was investigated.

No abstract

No abstract