Ultra-small manganese dioxide nanoparticles with high T 1 relaxivity for magnetic resonance angiography

Gadolinium (Gd)-based contrast agents (CAs) for clinical magnetic resonance imaging are facing the problems of low longitudinal relaxivity ( ) and toxicity caused by gadolinium deposition. Manganese-based small molecule complexes and manganese oxide nanoparticles (MONs) are considered as potential alternatives to Gd-based CAs due to their better biocompatibility, but their relatively low values and complicated synthesis routes slow down their clinical translation. Herein, we presented a facile one-step co-precipitation method to prepare MONs using poly(acrylic acid) (PAA) as a coating agent (MnO /PAA NPs), which exhibited good biocompatibility and high values. A series of MnO /PAA NPs with different particle sizes were prepared and the relationship between the particle size and was studied, revealing that the MnO /PAA NPs with a particle size of 4.9 nm exhibited higher . The finally obtained MnO /PAA NPs had a high value (29.0 Mn mM s ) and a low / ratio (1.8) at 1.5 T, resulting in a strong contrast enhancement. magnetic resonance angiography with Sprague-Dawley (SD) rats further proved that the MnO /PAA NPs showed better angiographic performance at low-dosage administration than commercial Gadovist® (Gd-DO3A-Butrol). Moreover, the MnO /PAA NPs could be rapidly cleared out after imaging, which effectively minimized the toxic side effects. The MnO /PAA NPs are promising candidates for MR imaging of vascular diseases.