Multifunctional NaYF4:Nd/NaDyF4 nanocrystals as a multimodal platform for NIR-II fluorescence and magnetic resonance imaging.

Abstract

Recently, multimodal imaging nanoprobes based on the complementary advantages of various imaging methods have attracted considerable attention due to their potential application in the biomedical field. As important bioimaging nanoprobes, lanthanide-doped nanocrystals (NCs) would be expected to improve the related biophotonic technology through integrated multimodal bioimaging. Herein, water-soluble and biocompatible NaYF4:Nd/NaDyF4 NCs were prepared by a solvothermal method combined with hydrophobic interaction with phospholipids as a capping agent. The NaYF4:Nd/NaDyF4 NCs exhibit excellent colloidal stability under physiological conditions. Compared with the bare NaYF4:Nd3+ NCs, the second near-infrared (NIR-II, 1000–1700 nm) fluorescence intensities of Nd3+ ions in the NaYF4:Nd/NaDyF4 core–shell NCs at the emissions of 1058 nm and 1332 nm are enhanced by 3.46- and 1.75-fold, respectively. Moreover, the r2 value of NaYF4:Nd/NaDyF4 NCs as T2-weighted contrast agents is calculated to be 44.0 mM−1 s−1. As a novel multimodal imaging nanoprobe, the NaYF4:Nd/NaDyF4 NCs can be employed for both NIR-II fluorescence and magnetic resonance imaging (MRI). The phospholipid-modified NaYF4:Nd/NaDyF4 NCs demonstrate in vitro and in vivo multimodal NIR-II fluorescence imaging and MRI of HeLa cells and tumors, respectively. This study provides an effective strategy for the development of novel multimodal probes for the medical application of nanomaterials.