Nanosized hybrid particles with double luminescence for biological labeling

Doubly luminescent core/shell structure nanoparticles were synthesized for biological detection. In the first step gadolinium oxide (Gd2O3) core doped with the luminescent Tb3+ ions was obtained by applying, with modifications, the polyol route, which allows direct precipitation of oxide nanoparticles in a polyalcohol medium. The presence of Tb3+ ions in the Gd2O3 crystalline matrix confers attractive optical properties for long-term studies and multilabeling such as a high photostability and narrow emission bands. The water sensitivity of these particles, which is detrimental for the Tb ion's luminescence, was overcome by embedding the oxide core in a functionalized polysiloxane shell prepared by hydrolysis condensation of a mixture of APTES and TEOS. This protective layer allows the dispersion of the particles in aqueous solution without loss of luminescence intensity. Moreover, the luminescence of polysiloxane-coated Gd2O3 nanoparticles is more intense than that in the case of the naked Gd2O3 core. Due to the presence of amino groups, organic dyes and biotargeting groups (nucleic acid, biotin, streptavidin) were covalently linked to the polysiloxane network. These particles are efficient for detection of biomolecules whose presence is revealed by the high fluorescence of organic dyes and/or the photostable Tb3+ ion's luminescence.