Preparation of linear poly(glycerol) as a T1 contrast agent for tumor-targeted magnetic resonance imaging.

Macromolecular contrast agents (CAs) labeled with targeting molecules are gaining remarkable interest as promising materials overcoming the defects of small-molecule CAs. Designed on the basis of biocompatible poly(glycerol) (PG), a linear macromolecular contrast agent (CA) was synthesized with a composition of PG as a backbone and partial hydroxyl connected with gadolinium labeled poly(l-lysine) dendrons, where folic acid was also conjugated. This linear CA exhibited higher relaxivity (7.04 mM^-1 S^-1) relative to Magnevist® (3.98 mM^-1 S^-1), and showed negligible toxicity determined by WST assay and histological analysis. In vitro and in vivo magnetic resonance imaging (MRI) measurements presented obvious target specificity to KB cells and tumor. Moreover, high signal enhancement was observed in the tumor region at various time points after intravenous injection to ensure the long time window for imaging. All the findings make it an attractive candidate for tumor-targeted MRI CAs.