A dual-mode T1 MRI/CT contrast agent of Gd2O3/Au@MSNs for tumor imaging with high performance

Magnetic resonance imaging (MRI) contrast agents with high relaxivity is of great importance for clinical diagnosis. Here we propose an effective method to enhance the relaxivity of MRI contrast agents. Ultra-small gadolinium oxide nanoparticles (Gd 2 O 3 NPs) with different surface ligands were prepared by coprecipitation method, and the polyacrylic acid (PAA) modulated Gd 2 O 3 NPs (PAA-Gd 2 O 3 ) have the high r 1 relaxivity of 53.34 mM –1 s –1 , which is mainly induced by the strong affinity between PAA and water molecules. In addition, PAA modulated Gd 2 O 3 NPs were successfully loaded on Au@MSNs (Au nanorod coated with mesoporous silica , Gd 2 O 3 /Au@MSNs) with enhanced affinity between Gd 3+ and water molecules, as well as increased motional time of Gd 3+ . Therefore, the r 1 relaxivity of Gd 2 O 3 /Au@MSNs can be up to 64.53 mM –1 s –1 , which is 17 times of the commercial agent Gd-DTPA. The Gd 2 O 3 /Au@MSNs NPs also have a low r 2 /r 1 of 1.04 and good computed tomography (CT) imaging performance, as well as good biocomatibility, which have great potential applications in multimodal bioimaging.