Compared with ultrasonography and magnetic resonance imaging (MRI), an obvious obstacle for fluorescent imaging is the limited tissue penetration depth. Development of deep-tissue fluorescent probes is thus of great interest, especially for in vivoapplications such as early-stage cancer diagnosis. Near-infrared (NIR) photons are less absorbed and scattered by tissues, fluorescence probes with excitation and emission in NIR could act as ideal probes for in vivo imaging with high sensitivity.Lanthanide ions with multiple and abundant f configurations, are the first choice of activators for luminescent materials. Here we introduce two types of NIR nanoprobes with two different intrinsic emissions from lanthanide ions. One is anti-stokes emission nanoparticles with Yb3+ and Tm3+ doping. With the stimulation at ca. 980 nm (Yb3+, 2F7/2�2F5/2), tow-photon upconverted emission at 800 nm (Tm3+, 3H4�3H6) is efficiently achieved. Another one is Nd3+ sensitized stokes emission of Yb3+. With the excitation of Nd3+ at 808 nm (4I9/2�4F5/2), not only emission of Nd3+ at 1064 nm (4F3/2�4I13/2) could be observed, the emission of Yb3+ at 975 nm (2F5/2�2F7/2) with could also be observed. This emission behavior comes from efficient energy transfer from Nb3+ to Yb3+. And the emission from Nd3+ and Yb3+ could be tuned with the doping ratio or core/shell structure design. To meet the requirements of in vivo imaging, these nanoparticles were dispersed in PBS buffer with removing the alkyl chain. The NIR imaging were obtained with subcutaneous injection and vein injection. The circulation and accumulation of the NPs could be examined in vivo. These NIR nanoprobes shows great advantage with higher quantum efficiency, lower tissue scattering than excitation or emission in visible range, and these may also make them a potential deep-tissue imaging probes.

Near-infrared lanthanide nanoprobes for deep-tissue in vivo imaging

247th National Meeting (2014)

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