title: Development of a quantum dot-based fluorescent immunoassay for progesterone determination in bovine milk.
abstract: The use of semiconductor quantum dots (QDs) as fluorescent labels to develop a competitive immunoassay for sensitive detection and quantification of progesterone in cow's milk is described. Colloidal water-soluble CdSe/ZnS QDs are conjugated to an antigen derivative (progesterone-BSA conjugate) and a simple methodology is optimised to determine the antigen concentration in the final bioconjugate. The obtained QD-linked antigens were then employed together with unlabelled anti-progesterone monoclonal antibodies, as the biological recognition elements, in the development of the quantitative QDs-based fluorescent immunoassay for progesterone in bovine milk. After optimization, the developed immunoassay proved to cover a progesterone concentration range from 0.3 to 14.5 ng/mL in cow milk. Milk samples were just diluted 10-fold with deionised water and directly analysed with the proposed immunoassay, without additional sample pre-treatment or analyte extraction. The minimum detectable level (IC(10)) of the developed immunoassay turned out to be 0.1 ng/mL of progesterone in bovine milk. The sensitivity (IC(50)) achieved was 2.2 ng/mL with a reproducibility of 3.5% RSD as obtained from the results of the analysis of the triplicate of same samples but in three different days. Applicability of the proposed methodology was evaluated by analyzing cow's milk samples enriched with known concentrations of progesterone and recoveries better than 90% were achieved.
authors.affiliation: Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julian Clavería, 8, 33006 Oviedo, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Trapiella-Alfonso
authors.forename: Jose M
authors.initials: JM
authors.lastname: Costa-Fernández
authors.forename: Rosario
authors.initials: R
authors.lastname: Pereiro
authors.forename: Alfredo
authors.initials: A
authors.lastname: Sanz-Medel
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000379:methods*; D002417:Cattle; D005456:Fluorescent Dyes / Q000737:chemistry*; D007118:Immunoassay / Q000379:methods; D057230:Limit of Detection; D008892:Milk / Q000737:chemistry*; D011374:Progesterone / Q000032:analysis* / Q000737:chemistry; D045663:Quantum Dots; D015203:Reproducibility of Results; D012710:Serum Albumin, Bovine / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D012710:Serum Albumin, Bovine; D011374:Progesterone