A Gd3Al tetranuclear complex as a potential bimodal MRI/optical imaging agent

Abstract

A new self-assembled gadolinium(III)–aluminum(III) complex (Gd₃Al) was synthesized and characterized. The efficacy of this Gd₃Al complex as a potential bimodal magnetic resonance imaging (MRI)/optical imaging agent has been evaluated. Relaxivity studies showed that the Gd₃Al complex has higher relaxation efficiency (7.18 mM⁻¹ s⁻¹) compared with the clinically used complex gadolinium–diethylenetriaminepentaacetic acid (Gd–DTPA, 3.9 mM⁻¹ s⁻¹) at 400 MHz and 25 °C. In vitro T₁-MR images on a 0.5 T magnetic field exhibited a remarkable enhancement of signal contrast for Gd₃Al compared to Gd-DTPA. Furthermore, the Gd₃Al complex exhibits bright-green luminescence with the emission spectrum centred at 510 nm. Live-cell fluorescence imaging reveals that the Gd₃Al complex is permeable to cells and localizes to the cytoplasm. In view of the relaxometric and luminescent properties, this Gd₃Al complex could serve as a potential bimodal MRI/optical imaging agent.