Biocompatible Nanoparticles of KGd(H₂O)₂[Fe(CN)₆]·H₂O with Extremely High <i>T</i>₁‑Weighted Relaxivity Owing to Two Water Molecules Directly Bound to the Gd(III) Center

A simple one-step method for preparing biocompatible nanoparticles of gadolinium ferrocyanide coordination polymer KGd­(H₂O)₂[Fe­(CN)₆]·H₂O is reported. The crystal structure of this coordination polymer is determined by X-ray powder diffraction using the bulk materials. The stability, cytotoxicity, cellular uptake, and MR phantom and cellular imaging studies suggest that this coordination-polymer structural platform offers a unique opportunity for developing the next generation of <i>T</i>₁-weighted contrast agents with high relaxivity as cellular MR probes for biological receptors or markers. Such high-relaxivity MR probes may hold potential in the study of molecular events and may be used for in vivo MR imaging in biomedical research and clinical applications

Imaging Metastasis Using an Integrin-Targeting Chain-Shaped Nanoparticle

While the enhanced permeability and retention effect may promote the preferential accumulation of nanoparticles into well-vascularized primary tumors, it is ineffective in the case of metastases hidden within a large population of normal cells. Due to their small size, high dispersion to organs, and low vascularization, metastatic tumors are less accessible to targeted nanoparticles. To tackle these challenges, we designed a nanoparticle for vascular targeting based on an α_vβ₃ integrin-targeted nanochain particle composed of four iron oxide nanospheres chemically linked in a linear assembly. The chain-shaped nanoparticles enabled enhanced “sensing” of the tumor-associated remodeling of the vascular bed, offering increased likelihood of specific recognition of metastatic tumors. Compared to spherical nanoparticles, the chain-shaped nanoparticles resulted in superior targeting of α_vβ₃ integrin due to geometrically enhanced multivalent docking. We performed multimodal <i>in vivo</i> imaging (fluorescence molecular tomography and magnetic resonance imaging) in a non-invasive and quantitative manner, which showed that the nanoparticles targeted metastases in the liver and lungs with high specificity in a highly aggressive breast tumor model in mice