Application Of Gadolinium Cluster Nanoparticles In MRI

Magnetic resonance imaging?MRI?,as a noninvasive and non-radiation imaging technology,offers significant advantages in many disease diagnosis,especially soft tissues disease,such as tumor.MRI contrast agents,which have been widely used in clinic,are able to produce robust contrast in MRI,which is a great help for diagnosis in clinic.Herein,a new kind of MRI contrast agent was developed.Firstly,two gadolinium cluster?Gd6 and Gd20?were synthesized.Then,by capping with poly?ethylene glycol?-derivatized poly?styrene-co-maleic anhydride??PSMA-PEG?,the Gd6-PSMA-PEG and Gd20-PSMA-PEG hydrophilic nanoparticles?NPs?can be prepared.The Gd6-PSMA-PEG NPs and Gd20-PSMA-PEG NPs with uniform distribution present a spherical shape.Hydrodynamic diameters of Gd6-PSMA-PEG NPs and Gd20-PSMA-PEG NPs were 110 and 284.3 nm respectively.The Gd6-PSMA-PEG NPs and Gd20-PSMA-PEG NPs exhibited high longitudinal relaxivity of 59.02 and 39.98 mM^-1 s^-1?0.5 T?and 18.68 and 19.83 mM^-1 s^-1?3 T?,respectively.While the commercial MRI agent,Magnevist,only exhibited a longitudinal relaxivity of 4.49?0.5 T?and 4.11 mM^-1 s^-1?3 T?.According to the Solomon-Bloembergen-Morgan?SBM?theory,the Gd6-PSMA-PEG NPs and Gd20-PSMA-PEG NPs high longitudinal relaxivity were contributed to their high rotational correlation time??_R?,low mean square zero field splitting?ZFS?energy??²?and low characteristic diffusion time??_D?.Robust contrast MRI were obtained when low dose Gd6-PSMA-PEG NPs?1/10 of the recommended dose for Magnevist?were intravenous injection of to the 4T1 tumor transplantation mice.