Тhe technology of creation and quality testing of immunofluorescent probes with dye alexa-488 for analysis of celular populations by flow cytometry

Fluorescent probes based on monoclonal antibodies (MAb) are widely used in scientific and clinical research in the field of oncology, hematology, immunology, epidemiology. Objective: to create of fluorescent probes based on the MAb and the fluorescent dye Alexa-488 for the analysis of cellular populations by flow cytometry. Materials and methods. MAb to B lymphocyte antigen (clone ICO-180), fluorescent dye Alexa-488 were used in the work. MAb was isolated from ascitic fluid by combined purification of the immunoglobulin fraction with caprylic acid and salting out with ammonium sulfate. Gel filtration on a PD-10 column was used to purify the conjugates (immunofluorescent probes, IFP), the concentration and labeling density of the IFP were determined spectrophotometrically. The determination of the working titer of the IFP was performed using the antibody titration method proposed by C.C. Stewart. Results. The optimal time of incubation of MAb with a fluorophore was experimentally determined. The optimal conditions for labeling MAb of the IСO series with the dye are: a carbonate buffer with pH 8,3, the concentration of antibodies in the reaction mixture is 1 mg/ml, molar ratio of active dye – 10–100 mmol per 1 mmol of protein, the incubation time is 90 minutes, the temperature is 18–25 °C. We obtained a panel of conjugates of MAb with Alexa-488, differing in their different labeling densities. Evaluation of the biological activity of the resulting conjugates was carried out on peripheral blood cells of donors in the concentration range of MAb 0,5–100 μg/ml. Conclusion. The optimal conditions for labeling MAb of the IСO series with the dye are: a carbonate buffer with pH 8,3, the concentration of antibodies in the reaction mixture is 1 mg/ml, the incubation time is 90 minutes, the temperature is 18–25 °C. The optimum density of labeling is in the range 5–13,5 M:M, the optimal concentration of antibodies is in the range of 5–25 μg/ml.

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