Supramolecular aggregates from polyacrylates and Gd(iii)-containing cationic surfactants as high-relaxivity MRI contrast agents†
The assembly behavior of narrowly dispersed poly(sodium acrylate) (PAAS) of different molecular weights with Gd(III)-containing cationic metallosurfactants (MS) was investigated by DLS, TEM and relaxivity plotting. The formed polyelectrolyte–surfactant complexes (PSCs) showed different structural patterns as the charge ratio increased from micellar to vesicular structures. SEM element mapping showed the presence of the gadolinium element in these complexes. An ICP-AES analysis further quantified the contents of Gd(III) in the PSCs. T1 magnetic resonance imaging (MRI) showed that these Gd(III)-loading complexes exhibited a relaxivity of up to 21.89 mM−1 s−1, much higher than that of Omniscan® (4.64 mM−1 s−1). A higher relaxivity was achieved with PAAS of higher molecular weight at the same charge ratio. The cytotoxicity test in vitro demonstrated the excellent biocompatibility of these PSCs, which is essential for clinical application.