Synthesis of an Amphiphilic Bis-Aqua Gd(OBETA) Complex for the Preparation of High-Relaxivity Supramolecular Magnetic Resonance Imaging Probes.

Prompted by the favourable relaxometric, thermodynamic and kinetic properties of the bis-hydrated Gd(OBETA) (OBETA=2,2'-oxybis(ethylamine)-N,N,N',N'-tetraacetic acid) complex, a novel derivative tailored with an n-hexadecyl chain was synthesised. The amphiphilic gadolinium complex was designed and prepared with the aim of obtaining high relaxivity supramolecular aggregates by self-assembly in micelles and liposomes. Thus, lipidic nanoparticles were prepared and characterised by dynamic light scattering and H NMR relaxometry. Relaxivity values of up to 48.3 mm  s (20 MHz and 298 K) were registered in liposomal aggregates. The binding to human serum albumin (HSA), evaluated both in terms of affinity and relaxometric properties of the supramolecular adduct, yielded exceptionally high relaxivity values (71.4 mm  s at 30 MHz and 298 K).