Department of Chemistry, National University of Singapore, Singapore, 117543, Singapore.
Centre for Inflammation Research, Queen's Medical Research Institute, The University of Edinburgh, EH16 4TJ, Edinburgh, UK.
Adv Mater. 2019 Sep;31(37):e1901851. doi: 10.1002/adma.201901851. Epub 2019 Jul 30.
The development of high-performance contrast agents in magnetic resonance imaging (MRI) has recently received considerable attention, as they hold great promise and potential as a powerful tool for cancer diagnosis. Despite substantial achievements, it remains challenging to develop nanostructure-based biocompatible platforms that can generate on-demand MRI signals with high signal-to-noise ratios and good tumor specificity. Here, the design and synthesis of a new class of nanoparticle-based contrast agents comprising self-assembled NaGdF and CaCO nanoconjugates is reported. In this design, the spatial confinement of the T source (Gd ions) leads to an "OFF" MRI signal due to insufficient interaction between the protons and the crystal lattices. However, when immersed in the mildly acidic tumor microenvironment, the embedded CaCO nanoparticles generate CO bubbles and subsequently disconnect the nanoconjugate, thus resulting in an "ON" MRI signal. The in vivo performance of these nanoconjugates shows more than 60-fold contrast enhancement in tumor visualization relative to the commercially used contrast agent Magnevist. This work presents a significant advance in the construction of smart MRI nanoprobes ideally suited for deep-tissue imaging and target-specific cancer diagnosis.
磁共振成像的新机遇
磁共振成像（MRI）中高性能对比剂的发展受到了广泛关注，因为它们有望成为癌症诊断的有力工具。尽管已经取得了很大的成就，但开发具有生物相容性的纳米结构平台仍然具有挑战性，这些平台能够以高信噪比和良好的肿瘤特异性产生按需 MRI 信号。在此，报道了一类由自组装的 NaGdF 和 CaCO 纳米复合物组成的新型纳米粒子基对比剂的设计和合成。在该设计中，由于质子与晶格之间的相互作用不足，T 源（Gd 离子）的空间限制导致 MRI 信号“关闭”。然而，当浸入轻度酸性的肿瘤微环境中时，嵌入的 CaCO 纳米颗粒会产生 CO 气泡，并随后断开纳米复合物，从而导致 MRI 信号“打开”。这些纳米复合物的体内性能显示，与商用对比剂 Magnevist 相比，肿瘤可视化的对比度增强了 60 多倍。这项工作在构建智能 MRI 纳米探针方面取得了重大进展，这些探针非常适合深层组织成像和靶向癌症诊断。
