A novel heterobimetallic Ru(ii)–Gd(iii) complex-based magnetoluminescent agent for MR and luminescence imaging

Abstract

A novel heterobimetallic ruthenium(II)–gadolinium(III) complex, Ru–Gd, comprising a luminescent Ru(II) complex, [Ru(bpy)₂(phen)]²⁺ (bpy: 2,2′-bipyridine; phen: 1,10-phenanthroline), and a Gd(III) complex, DOTA–Gd³⁺ (DOTA: 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), has been designed and synthesized as a magnetoluminescent dual-modal imaging agent. The heterobimetallic complex Ru–Gd is water-soluble, biocompatible with low cytotoxicity, strongly luminescent with a long luminescence lifetime and a large Stokes shift, and has comparable longitudinal relaxivity r₁ (4.71 mM⁻¹ s⁻¹), which enable the complex to be suitable for luminescence bioimaging and T₁-weighted MR imaging. Using Ru–Gd as a contrast agent, the T₁-weighted MRI of a Kunming (KM) mouse was successfully carried out. The results demonstrated the availability and validity of our approach for the development of magnetoluminescent dual-modal imaging agents.