Pyclen-based Gd complex with ionisable side-chain as a contrastophore for the design of hypersensitive MRI nanoprobes: synthesis and relaxation studies

Abstract A straightforward method for synthesizing at the multigram scale a low molecular weight PCTA–based gadolinium complex bearing an ionizable oxyacetic chain on the pyridine unit was described, together with its encapsulation within a nanohydrogel matrix. The ionic gelation occurred between chitosan and hyaluronic acid, reinforced by crosslinking with sodium tripolyphosphate. The resulting nanogels are spherical and narrowly monodisperse. They are stable for at least four months at room temperature in water and in media of higher ionic strength (NaCl 0.9%, PBS). They display an enhanced longitudinal relaxivity r1 of 15.9 and 12.1 mM-1.s-1 at 20 MHz and 60 MHz at 37 °C respectively which is at least 4 times higher than that of DOTAREM®.