Nanoscale metal-organic frameworks as potential multimodal contrast enhancing agents

Abstract

Nanoscale metal-organic frameworks (NMOFs) based on Gd3+ centers and benzenedicarboxylate and benzenetricarboxylate bridging ligands were synthesized using reverse microemulsions and characterized using SEM, PXRD, and TGA. These NMOFs exhibit extraordinarily large R1 and R2 relaxivities because of the presence of up to tens of millions of Gd3+ centers in each nanoparticle and are thus efficient T1 and T2 contrast agents for MRI. The NMOFs can also be made highly luminescent by doping with Eu3+ or Tb3+ centers. The results from this work suggest that NMOFs can be used as potential contrast agents for multimodal imaging.

Figure 1

SEM images of Gd(BDC)_1.5(H₂O)₂ (1) nanorods synthesized with w=5 (left) and w=10 (right).

Figure 2

SEM images of irregularly-shaped, crystalline [Gd(1,2,4-BTC)(H₂O)₃]•H₂O (2) nanoplates.

Figure 3

(a) R1 and R2 relaxivity curves of 1 of ∼100 nm in length by ∼40 nm in diameter. (b) R1 and R2 relaxivity curves of 1 of ∼1 μm in length by ∼100 nm in diameter. In comparison, OmniScan gave an R1 of 4.1 mM⁻¹•s⁻¹ under these conditions. (c) T1-weighted MR images of suspensions of 1 in water containing 0.1% xanthan gum. (d) Luminescence images of ethanolic suspensions of 1, 1a (1 doped with 5 mol% Eu³⁺), and 1b (1 doped with 5 mol% Tb³⁺).