Preparation And Application Of Long-wavelength-excited Luminescent Europium Nanoparticles

The time-resolved luminescence bioassays based on long-lifetime lanthanide complexes can effectively eliminate the background fluorescence from biological samples, and have been widely applied in clinic diagnosis and life sciences. However, the excitation wavelength of the most lanthanide luminescent biolabels are confined within the UV region (below360nm), which poses phototoxicity on biological samples and block the applications of time-resolved luminescence bioassays. Thus, it is quite desirable to develop long-wavelength-excited and water-soluble luminescent biolabels with high quantum yield and long lifetime for the improvement of time-resolved luminescence bioassays.In this work, two new ternary europium complexes have been synthesized based on ligands2’-(N,N-diethylanilin-4-yl)-4’,6’-bis(3"-methoxycarbonylpyrazol-1"-y1)-1,3’,5’-triazine (MCPBT) and2-(V,N-diethylanilin-4-y1)-4,6-bis(3-carboxylpyrazol-1"-y1)-1’,3’,5’-triazine (DPCT), respectively. By using a covalent binding-copolymerization method, two kinds of silica-based europium (Ⅲ) luminescent nanoparticles were prepared in a water-in-oil (W/O) microemulsion. One kind of nanoparticles can be excited at384nm and have long lifetime (369μs), high quantum yield (25.3%) and uniform size, ca.38nm in diameter. The maximum wavelength of the other kind of luminescent nanoparticles is337nm, and the excitation window can be extended to450nm. It can emit decent luminescence even when excited by400nm light. The nanoparticles also possesses long lifetime (402μs), high quantum yield (32.0%) and uniform size, about34nm in diameter. Both of the two kinds of nanoparticles are monodisperse spherical with primary amino groups introduced to their surface which enable the nanoparticles to be used directly as biolabels. The new nanoparticles were successfully used for streptavidin labeling and time-gated luminescence imaging of an environmental pathogen, cryptosporidium muris. The results suggest that the developed long-wavelength-excited europium luminescent nanoparticles can be used as new biolabels for time-gated luminescence bioassays.