Preparation, characterization and application of fluorescent terbium complex-doped zirconia nanoparticles.

Novel zirconia-based fluorescent terbium nanoparticles have been prepared as a fluorescent nanoprobe for time-resolved fluorescence bioassay. The nanoparticles were prepared in a water-in-oil (W/O) microemulsion consisting of a strongly fluorescent Tb(3+) complex, N,N,N(1), N(1)-[2,6-bis(3'-aminomethyl-1'-pyrazolyl)-phenylpyridine]tetrakis(acetate)-Tb(3+)(BPTA-Tb(3+)), Triton X-100, hexanol, and cyclohexane by controlling co-condensation of Zr(OCH(2)CH(3))(4) and ZrOCl(2.) The characterizations by transmission electron microscopy and fluorometric methods indicate that the nanoparticles are uniform in size, 33+/- 4 nm in diameter, and have a fluorescence quantum yield of 8.9% and a long fluorescence lifetime of 2.0 ms. The zirconia-based fluorescent terbium nanoparticles show high stability against basic dissolution in a high pH aqueous buffer compared to the silica-based nanoparticles. A surface modification and bio-conjugation method for the fluorescent nanoparticles was developed, and the nanoparticle-conjugated streptavidin (SA) was used for time-resolved floro-immunoassy (TR-FIA) of human prostate specific antigen (PSA). The result shows that the zirconia-based fluorescent terbium nanoparticles are useful as a fluorescent nanoprobe for time-resolved fluorescence bioassay.