Application of gold nanoparticles produced by laser ablation for immunochromatographic assay labeling.

Nanodispersed gold is widely used as a marker in different analytical systems. For such purposes, it is usually obtained by the reduction of salts. This work studied the potential analytical applications of nanodispersed gold obtained by laser ablation because gold produced with this method has no chemical coating. The nanoparticles produced were characterized by transmission electron microscopy and spectrophotometry. The average size of the particles was 24.5 nm. Concentration dependences of antibody immobilization on ablative gold were obtained. With the use of antibody-conjugated nanoparticles, an immunochromatographic system was constructed for the detection of zearalenone mycotoxin. This immunoassay was characterized by a detection limit of 0.1 ng/ml antigen with an assay duration of only 15 min, which is on par with current test systems comprising nanodispersed gold obtained by chemical reduction. The simplicity of ablative dispersing makes this a prospective method for the labeling of various antibodies for analytical use.

[Immunochromatographic Test System for the Detection of T-2 Toxin].

An immunochromatographic test system was developed for the detection of T-2 toxin (T2T), which is one of priority contaminants of cereals. The detection is based on the competition between T2T in the sample and the T2T-protein conjugate immobilized on the test strip for the binding to the complexes of anti-T2T antibodies with gold nanoparticles serving as the marker. The results of the competition are recorded as the coloration in the test zone of the test strip produced by the marker. The optimum dilution of the sample for the reliable high-sensitivity analysis corresponds to the final methanol concentration equal to 20%. The deceleration of the movement of reactants along the test strip due to the use of additional membranes impregnated with 10% BSA resulted in the decrease in the detection limit of T2T. The test system was examined for the detection of T2T in water-methanol extracts of maize grains. The disappearance of the color in the test zone, which attests to the presence of mycotoxin, was observed for grain samples containing T2T at a concentration of 53 µg/kg or more (the final T2T concentration in the immunochromatorgaphic assay is 3 ng/mL). The video-digital detection limit of T2T is 16 µg/kg (0.9 ng/mL). The duration of the assay is 15 min. The results of the present study suggest that the developed test system is suitable for the control of the maximum allowable T2T content.