Simple, rapid, and sensitive thyroid-stimulating hormone immunoassay using europium(III) nanoparticle label

Thyroid-stimulating hormone (TSH) is widely used as a marker of thyroid function. A rapid TSH assay enables diagnosis during the first visit at the doctor’s office aiding to faster and cost-effective medical treatment. To accomplish such an assay method europium(III) chelate nanoparticles were coated with anti-TSH monoclonal antibody. Captured anti-TSH monoclonal antibody was immobilized onto single wells by streptavidin–biotin chemistry and the assay was carried out in dry chemistry format using 5 (mu)l of sample in a 30 (mu)l assay volume in the commercial AiO immunoassay system. The developed TSH nanoparticle assay was performed in a kinetic mode using a 10-min incubation time. The analytical sensitivity of the developed assay was 0.0012 mIU l^-1 corresponding to the fourth generation TSH assay and less than 0.02 mIU l^-1 when serum-based matrix was used for calibrators. The dynamic range of the assay was more than three orders of magnitude and no high-dose hook effect was observed at 100 mIU l^-1 of TSH. Correlation with an automated commercial assay was good (y = 0.96 (plus-minus) 0.02, INTERCEPT = 0.12 (plus-minus) 0.09, Sy|x = 0.49, R = 0.988). Intra- and interassay variations were 4–14 and 6–17%, respectively. The developed quantitative one-step all-in-one dry reagent time-resolved fluorometric immunoassay has great potential for rapid analysis of serum thyroid-stimulating hormone in a point-of-care environment when antibody-coated high specific activity Eu(III) nanoparticles were used as labels.