Anchoring Group Mediated Radiolabeling for Achieving Robust Nanoimaging Probes

Abstract

Radiolabeling counts for much in the functionalization of inorganic nanoparticles (NPs) because it endows NPs with high‐sensitive imaging capacities apart from providing accurate pharmacokinetic information on the labeled particles, which makes the development of relevant radiolabeling chemistry highly desirable. Herein, a novel Ligand Anchoring Group MEdiated RAdioLabeling (LAGMERAL) method is reported, in which a polyethylene glycol (PEG) ligand with a diphosphonate (DP) terminal group plays a key role. It offers possibilities to radiolabel NPs through the spare coordination sites of the DP anchoring group. Through X‐ray absorption spectroscopy studies, the coordination states of the foreign metal ions on the particle surface are investigated. In addition, radioactive Fe3O4 NPs are prepared by colabeling the particles with 125I at the outskirt of the particles through a phenolic hydroxyl moiety of the PEG ligand, and 99mTc at the root of the ligand, respectively. In this way, the stabilities of these types of radiolabeling are compared both in vitro and in vivo to show the advantages of the LAGMERAL method. The outstanding stability of probe and simplicity of the labeling process make the current approach universal for creating advanced NPs with different combinations of functionalities of the inorganic NPs and radioactive properties of the metal radioisotopes.

Anchoring Group-Mediated Radiolabeling of Inorganic Nanoparticles─A Universal Method for Constructing Nuclear Medicine Imaging Nanoprobes

“…37−39 Very recently, we have developed a third radiolabeling method, that is, ligand anchoring group-mediated radiolabeling (LAGMERAL) method, that has been demonstrated by labeling Fe 3 O 4 nanoparticles with 99m Tc. 40 This new labeling method relies on the coordination between the metal radioisotope and the spare −P−O − and −PO moieties of the diphosphonate anchoring groups of the polyethylene glycol (PEG) ligands that render Fe 3 O 4 nanoparticles water-soluble and biocompatible. Compared to 125 I labeling via the phenolic hydroxyl moiety on the other side of the PEG ligand, the 99m Tc labeling at the root of the PEG ligand exhibited better stability both in vitro and in vivo.…”

Methods for Radiolabelling Nanoparticles: SPECT Use (Part 1)

“…The radiolabelling stability was evaluated by incubating the NPs in a foetal bovine serum (FBS) solution. Results showed a radiochemical purity of 93.8% after 6 h and 89.1% after 72 h [ 38 ]. NaGdF 4 :Yb,Tm NPs were synthesised by the thermal decomposition method and then labelled with 99m Tc through the LAGMERAL method, where the surface hydrophobic oleate ligand was replaced with DP-PEG-mal.…”

Methods for Radiolabelling Nanoparticles: PET Use (Part 2)

“…These were initially labelled with 99m Tc as proof of concept, and then, they were labelled with 68 Ga. This method is based on the interaction between the metal radioisotope and the diphosphonate anchoring groups of the PEG-coated NPs [ 41 , 42 ].…”