Synthesis and characterization of europium(III) nanoparticles for time-resolvedfluoroimmunoassay of prostate-specific antigen

Abstract

Recent advances in the fabrication and bioconjugation of nanometre-sized lanthanide(III)chelate particles have led to robust high specific activity labels. This paper describes thesynthesis and characterization of lanthanide(III) nanoparticle labels and the use ofa nanoparticle in a bioaffinity assay system. Two europium(III) nanoparticleswere prepared using an extremely simple, inexpensive and fast agglomerationstrategy. A silica-stabilized nanoparticle was synthesized from hydrophobictris(dibenzoylmethane)–mono(phenanthroline) and tris(dibenzoylmethane)–mono(5-aminophenanthroline)europium(III) chelates in aqueous solution. In addition, a naphthoyltrifluoroacetone:tri-n-octylphosphineoxide:sodium dodecyl sulfate europium(III) complex was agglomerated inwater. The particle sizes ranged from 62 to 140 nm in diameter. The silica-stabilized particlewas further coated with a monoclonal antibody. The analytical performance of thebioconjugated nanoparticle label was evaluated in a model sandwich immunoassay ofprostate-specific antigen. The detection limit of human prostate-specific antigen was28 ng l−1, 850 fM, in a microtiter plate format using time-resolved fluorometry. The coefficient ofvariation ranged from 1 to 9%. The novel nanoparticle label improves the specific activityof existing lanthanide(III) nanoparticle labels and simplifies the preparation route. Inaddition, prepared high-density nanoparticle labels using lanthanide(III) chelates orother specific fluorochromes have potential applications in a number of otherfields.