Functionalized fluorescent core-shell nanoparticles used as a fluorescent labels in fluoroimmunoassay for IL-6

Nanoparticle labels conjugated with biomolecules are used in a variety of different assay applications. In this paper, a sensitive fluoroimmunoassay for recombinant human interleukin-6 (IL-6) with the functionalized Rubpy-encapsulated fluorescent core-shell silica nanoparticles labeling technique has been proposed. IL-6 was measured based on the specific interaction between captured IL-6 antigen and functionalized fluorescent core-shell nanoparticles-labeled anti-IL-6 monoclonal antibody. The calibration graph for IL-6 was linear over the range 20–1250 pg ml−1 with a detection limit of 7 pg ml−1 (3σ). The regression equation of the working curve is IF = 7.665 + 32.499 [IL-6] (ng ml−1) (r = 0.9980). The relative standard deviation (R.S.D.) for 11 parallel measurements of 78 pg ml−1 IL-6 was 3.2%. Furthermore, the application of fluorescence microscopy imaging in the study of the antibody labeling and sandwich fluoroimmunoassay with the functionalized fluorescent core-shell silica nanoparticles was also explored. This proposed method has the advantage of showing the specificity of immunoassay and sensitivity of fluorescent nanoparticle labels technology. The results demonstrate that the method offers potential advantages of sensitivity, simplicity and reproducibility for the determination of IL-6, and is applicable to the determination of IL-6 in serum samples and enabling fluorescence microscopy imaging for the determination of IL-6.