An ultrasensitive detection of 17β-estradiol using a gold nanoparticle-based fluorescence immunoassay.

A novel ultrasensitive amplification immunoassay for the determination of 17β-estradiol (E2) is reported based on the nanoparticle signal amplification platform. It involves two types of particles: magnetic microparticles (MMPs) functionalized with an anti-E2 antibody produced in rabbit as a capture probe; double-codified gold nanoparticles (DC-AuNPs) modified with both goat anti-rabbit antibody and SH-dsDNA-biotin as a signal amplifier; and avidin-FITC was added to link to the SH-dsDNA-biotin as a tracer. The competitive reaction of the anti-E2 antibody immobilized on magnetic microparticles with estradiol in the sample solution and with the goat anti-rabbit antibody on double-codified gold nanoparticles results in a complex involving the DC-AuNPs and MMPs. Under optimized conditions, the linear range of E2 is from 1.0 × 10(-5) to 1.0 ng mL(-1), and the detection limit of the assay could reach up to 6.37 × 10(-6) ng mL(-1). It was applied to determine E2 in human urine, with mean percent recoveries in the range of 96.5%-107.4%, and relative standard deviations were below 8.1%.