Activatable Lanthanide Nanoprobes with Dye-Sensitized Second Near-Infrared Luminescence for <i>in Vivo</i> Inflammation Imaging
Jinzhao Huang, Xuefei Zhang, Shiyu Li, Fei Qu, Biao Huang, Ran Cui, Yijing Liu, Wenbo Hu, Xiangliang Yang, Yan Zhang
Abstract
Lanthanide nanoparticles exhibit unique photophysical properties and thus emerge as promising second near-infrared (NIR-II) optical agents. However, the limited luminescence brightness hampers their construction of activatable NIR-II probes. Herein, we report the synthesis of dye-sensitized lanthanide nanoprobes (NaGdF 4:Nd/ICG; indocyanine green (ICG)) and their further development for in vivo activatable imaging of hypochlorite (ClO – ). Dye sensitization using ICG not only shifts the optimal doping concentration of Nd 3+ from 5 to 20 mol % but also leads to a 5-fold NIR-II enhancement relative to the ICG-free counterpart. Mechanistic studies reveal that such a luminescence enhancement of NaGdF 4:Nd at high Nd 3+ concentration is ascribed to an alleviated cross-relaxation effect due to the broad absorption of ICG and faster energy transfer process. Taking advantage of dye oxidation, the nanoprobes enable activatable NIR-II imaging of hypochlorous acid (ClO – ) in a drug-induced lymphatic inflammation mouse model. This work thus provides a simple, yet effective luminescence enhancement strategy for constructing lanthanide nanoprobes at higher activator doping concentration toward activatable NIR-II molecular imaging.