1H NMR RELAXIVITY OF NOVEL COLLOIDAL NANOSTRUCTURED Gd(III)-BASED POTENTIAL CONTRAST AGENTS

Novel nanostructured potential contrast agents were prepared following a recently reported procedure [1- 3] in which water insoluble Gd(III) complexes, with ligands based either on thiacalix[4]arene or tetrahydroxy-calix[4]arene (Figure 1), self-assemble into nanosized particles by precipitation from an organic to an aqueous phase and form stable colloids by coating with poly(sodium styrene sulfonate). The longitudinal (r1) and transverse (r2) relaxivities of the colloidal systems were measured at 20.8 MHz. 1H FFC NMR relaxometry was applied to determine r1 as a function of Larmor frequency in the 10 kHz to 40 MHz range. Relaxivity dispersions, showing a maximum at around 20-30 MHz (Figure 2), clearly indicated the effective incorporation of the Gd(III) complexes into nanostructures. Their analysis allowed the mechanism at the basis of contrast enhancement and the key factors affecting the contrast efficiency to be highlighted. References [1] N. A. Shamsutdinova et al., ChemistrySelect, 2016, 1, 1377-1383. [2] R. Zairov et al., Sci. Rep., 2017, 7, 40486. [3] R. Zairov et al., Sci. Rep., 2017, 7, 14010.