Abstract: A novel immunofluorescence microscopic method for a neutrophil and somatic cell count was developed by using anti-elastase antibody. Two different conjugates - anti-bovine neutrophil elastase antibody-fluorescein isothiocyanate conjugate and anti-bovine neutrophil elastase antibody-Quantum Dots 710nm conjugate were prepared. The coupling of Quantum Dots (QDs) and fluorescein isothiocyanate (FITC) to antibody has been demonstrated by comparison of ultraviolet absorption spectra and fluorescence spectra of conjugate and initial components. The activities of conjugates were measured by indirect ELISA at the same conditions. It was found that the sensitivity of the immunoassay with QDs-conjugate was higher than the sensitivity of the immunoassay with FITC-conjugate. The storage stability of anti- bovine neutrophil elastase antibody-QDs710nm conjugate and anti-bovine neutrophil elastase antibody-FITC conjugate was studied. The residual fluorescence intensity of anti-elastase antibody-QDs was 95% at 30th day, while the intensity of anti- elastase antibody-FITC conjugate was reduced to 60% at same day. The obtained conjugates were applied in real test with bovine milk somatic cells. The fluorescence imaging proved that QDs-conjugate has better fluorescence intensity than the FITC- conjugate, and is more appropriate for determination of somatic cells in milk.

Keywords: Quantum Dots; FITC; Antibody; Conjugate; Somatic cells;


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