A Novel Immunoassay Method for Cd2+ Detection Based on Up-Conversion Nanoparticles and Gold Nanoparticles

Abstract:

A immunoassay platform for Cd²⁺ was constructed based on fluorescence resonance energy transfer (FRET) between the up-conversion nanoparticles (UCNPs) and the gold nanoparticles (AuNPs) and the recognition of antigen and antibody. Water-soluble UCNPs modified with Cd-antigen were prepared as the energy donor probe, and AuNPs modified by Cd-antibody were synthesized as the energy receptor probe. The immune binding of antigen-antibody triggered FRET process of UCNPs and AuNPs, causing fluorescence quenching of UCNPs. In the presence of Cd²⁺, Cd²⁺ competitively bound to AuNPs-antibody with UCNPs-antigen, which inhibited the FRET process, and the fluorescence signal value enhanced with the increase of Cd²⁺ concentration. The results showed that the detection range was from 0.01 ng/mL to 10 ng/mL, and the detection limit was 0.01 ng/mL. The method was applied to the detection of Cd²⁺ in tap water samples. At the spiked level of 0.1, 1, 10 ng/mL, the recoveries for Cd²⁺ ranged from 98% to 109% with the relative standard deviations (RSDs) of 3.4% to 4.1%.