Oligoethylenimine-Grafted Chitosan as Enhanced T-1 Contrast Agent for In Vivo Targeted Tumor MRI

Purpose: To synthesize and characterize an effective macromolecular magnetic resonance imaging (MRI) contrast agent based on oligoethylenimine-grafted chitosan with targeting capability. Materials and Methods: In this study we synthesized and characterized oligoethylenimine-grafted chitosan copolymers, followed by conjugating with Gd-DTPA and folic acid. The toxicity was evaluated by WST assay, and in vitro MRI studies were performed in comparison with Gd-DTPA. Finally, the contrast enhancement of the new macromolecular MRI contrast agent was then evaluated in the mice bearing KB xenografts. Results: Compared to Gd-DTPA (4.3 mM(-1) s(-1)), this macromolecular contrast agent (mCA) exhibited much higher T-1 relaxivity (14.4 mM(-1) s(-1)), up to 3.3 times higher. Meanwhile, the WST assay illustrated that the viability of KB cells remained at 90% even when the Gd concentration was 1 mM. During the in vivo study, the image contrast produced by FA-mCA was higher than one produced by mCA, up to 2.5 times higher. Conclusion: Our results showed this macromolecular contrast agent has potential for developing sensitive and biocompatible MRI probe with targeting capability