High-Relaxivity Gd(III)–Hemicryptophane Complex

Self-Assembly of Lanthanide-Covalent Organic Polyhedra: Chameleonic Luminescence and Efficient Catalysis

A series of multinuclear lanthanide-covalent organic polyhedra (LnCOPs), including pillar-typed triangular prisms 1-Ln₃ and tetrahedra 2-Ln₄ (Ln = La^III, Sm^III, Eu^III), have been constructed for the first time, through either one-pot subcomponent self-assembly or postassembly metalation. In contrast to the known tetrahedral cages based on transition metals, the pillar-typed polyhedra were favored from the same organic components in the presence of lanthanides. Besides this, facile transmetalations between the 1-Ln₃ polyhedra endow cascade chameleonic luminescence. Meanwhile, the open metal sites and pendent amine groups on 1-Ln₃ enable these polyhedra to catalyze the Henry reaction efficiently.

Enhancing the magnetic relaxivity of MRI contrast agents via the localized superacid microenvironment of graphene quantum dots

The design of contrast agents (CAs) with high magnetic relaxivities is a key issue in the field of magnetic resonance imaging (MRI). The traditional strategy employed is aimed at optimizing the structural design of the magnetic atoms in the CA. However, it is difficult to obtain an agent with magnetic relaxivity over 100 mM^-1 s^-1 using this approach. In this work, we demonstrate that modulation of the localized superacid microenvironment of certain CAs (Gd³⁺ loaded polyethylene glycol modified graphene oxide quantum dots or 'GPG' for short) can effectively enhance the longitudinal magnetic relaxivities (r₁) by accelerating proton exchange. r₁ values of a series of GPGs are significantly increased by 20-30 folds compared to commercially available CAs over a wide range of static magnetic field strengths (e.g. 210.9 mM^-1 s^-1vs. 12.3 mM^-1 s^-1 at 114 μT, 127.0 mM^-1 s^-1vs. 4.9 mM^-1 s^-1 at 7.0 T). GPG aided MRI images is then acquired both in vitro and in vivo with low biotoxicities. Furthermore, folic-acid-modified GPG is demonstrated suitable for MRI-fluorescence dual-modal tumor targeting imaging in animals with more than 98.3% specific cellular uptake rate.