Preparation and Time-Resolved Luminescence Bioassay Application of Multicolor Luminescent Lanthanide Nanoparticles

Because highly luminescent lanthanide compounds are limited to Eu³⁺ and Tb³⁺ compounds with red (Eu, ˜615 nm) and green (Tb, ˜545 nm) emission colors, the development and application of time-resolved luminescence bioassay technique using lanthanide-based multicolor luminescent biolabels have rarely been investigated. In this work, a series of lanthanide complexes covalently bound silica nanoparticles with an excitation maximum wavelength at 335 nm and red, orange, yellow and green emission colors has been prepared by co-binding different molar ratios of luminescent Eu³⁺-Tb³⁺ complexes with a ligand N,N,N¹,N¹-(4′-phenyl-2,2′:6′,2′′-terpyridine-6,6′′-diyl)bis(methylenenitrilo) tetrakis (acetic acid) inside the silica nanoparticles. The nanoparticles characterized by transmission electron microscopy and luminescence spectroscopy methods were used for streptavidin labeling, and time-resolved fluoroimmunoassay (TR-FIA) of human prostate-specific antigen (PSA) as well as time-resolved luminescence imaging detection of an environmental pathogen, Giardia lamblia. The results demonstrated the utility of the new multicolor luminescent lanthanide nanoparticles for time-resolved luminescence bioassays.