Positive and Negative Lattice Shielding Effects Co-existing in Gd (III) Ion Doped Bifunctional Upconversion Nanoprobes

Authors

  • Feng Chen,

    1. Group of Mesoporous and Low-Dimensional Nano-materials, State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, P.R. China
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  • Wenbo Bu,

    Corresponding author
    1. Group of Mesoporous and Low-Dimensional Nano-materials, State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, P.R. China
    • Group of Mesoporous and Low-Dimensional Nano-materials, State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, P.R. China.
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  • Shengjian Zhang,

    1. Department of Radiology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, P.R. China
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  • Xiaohang Liu,

    1. Department of Radiology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, P.R. China
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  • Jianan Liu,

    1. Group of Mesoporous and Low-Dimensional Nano-materials, State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, P.R. China
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  • Huaiyong Xing,

    1. Group of Mesoporous and Low-Dimensional Nano-materials, State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, P.R. China
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  • Qingfeng Xiao,

    1. Group of Mesoporous and Low-Dimensional Nano-materials, State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, P.R. China
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  • Liangping Zhou,

    1. Department of Radiology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, P.R. China
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  • Weijun Peng,

    1. Department of Radiology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, P.R. China
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  • Lianzhou Wang,

    1. Chemical Engineering and ARC Centre of Excellence for Functional Nanomaterials, The University of Queensland, St. Lucia, QLD 4072, Australia
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  • Jianlin Shi

    Corresponding author
    1. Group of Mesoporous and Low-Dimensional Nano-materials, State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, P.R. China
    • Group of Mesoporous and Low-Dimensional Nano-materials, State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, P.R. China.
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Abstract

Gadolinium (Gd) doped upconversion nanoparticles (UCNPs) have been well documented as T1-MR and fluorescent imaging agents. However, the performance of Gd3+ ions located differently in the crystal lattice still remains debatable. Here, a well-designed model was built based on a seed-mediated growth technique to systematically probe the longitudinal relaxivity of Gd3+ ions within the crystal lattice and at the surface of UCNPs. We found, for the first time, a nearly 100% loss of relaxivity of Gd3+ ions buried deeply within crystal lattices (> 4 nm), which we named a “negative lattice shielding effect” (n-LSE) as compared to the “positive lattice shielding effect” (p-LSE) for the enhanced upconversion fluorescent intensity. As-observed n-LSE was further found to be shell thickness dependent. By suppressing the n-LSE as far as possible, we optimized the UCNPs' structure design and achieved the highest r1 value (6.18 mM−1s−1 per Gd3+ ion) among previously reported counterparts. The potential bimodal imaging application both in vitro and in vivo of as-designed nano-probes was also demonstrated. This study clears the debate over the role of bulk and surface Gd3+ ions in MRI contrast imaging and paves the way for modulation of other Gd-doped nanostructures for highly efficient T1-MR and upconversion fluorescent bimodal imaging.

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