Luminescent immunochromatography based on Eu3+ coordination compounds for detection of pathogenic microorganisms and bacterial toxins

Introduction . Increasing the sensitivity of immunochromatographic assay as an express method for detection and diagnosis of pathogenic microorganisms and toxins is a relevant task with regard to ensuring food safety and population health in general. Objective. Development of a prototype of a video digital recorder of luminescent immunochromatograms (RLI-Eu 3+ ) and luminescent immunochromatographic tests (LICHT) adapted to a device based on microspheres with europium compounds. Comparison of the sensitivity of LICHT and AuNPs-based immunochromatography assay (ICA) tests to increase the sensitivity of the method for detection of pathogenic microorganisms and their toxins. Material and methods . Submicron polymer microspheres labeled with organic complexes of trivalent europium (Eu 3+ ) were used as a luminescent label for immunochromatography. LICHT were recorded using the developed RLI-Eu 3+ recorder. Results. The detection threshold of the Eu 3+ luminescent complex on the immunochromatographic membrane was shown to be 2 pg/mm 2 , with the linearity of the readings ranging within 2–200 pg/mm 2 . The coefficients of variation of the instrument readings in the luminescent complex concentration range of 20–200 pg/mm 2 and 2–20 pg/mm 2 were found to be less than 5% and 10%, respectively. Using LICHT and the RLI-Eu 3+ device, detection thresholds were determined as follows: cholera toxin — 10 ng/mL, staphylococcal enterotoxin type B — 0.5 ng/mL, plague pathogen cells — 1×10 3 cells/mL, anthrax pathogen spores — 5×10 3 spores/mL, Crimean-Congo hemorrhagic fever (CCHF) virus antigens — at a dilution of 1:640,000. Conclusions. The developed video digital recorder RLI-Eu 3+ and LICHT based on europium coordination compounds enabled the detection threshold of pathogenic microorganisms and bacterial toxins to be reduced by 20–128 times compared to immunochromatographic tests based on colloidal gold (CG) for the same pathogens.