Hybrid Dextran-gadolinium Nano-suitcases as High-relaxivity MRI Contrast Agents

Dextran-poly(glycidyl methacrylate) (Dex-PGMA) nano-suitcases were synthesized efficiently via a graft copolymerization induced self-assembly (GISA) approach. On this basis, the Dex-PGMA nano-suitcases were modified with hydrazide, and the attachment of multiple chelated Gd(III) ions to the interior of the nano-suitcases affords nanoscale MRI contrast agents with high relaxivity values. The highly fenestrated dextran shell of the nano-suitcases assures water exchange which readily occurs between the surrounding environment and the Gd(III) ions encapsulated within the hybrid nano-suitcases. The complexation between the hydrophilic hydrazide interior of the nano-suitcases and Gd(III) ions results in an impressive Gd payload at 22.6 wt% in the hybrid nano-suitcases. The longitudinal relaxivity (r1) of the hybrid nano-suitcases is reported as 44.4 L/(mmol·s), which is 9–14 folds of that of commercial Gd-DTPA agents. In vivo MRI studies demonstrate that the hybrid nano-suitcases accumulated in the lymph node of the rat due to their nanoscale dimensions and displayed strong signals in vivo . The results indicated that the hybrid nano-suitcases provide a promising platform for the diagnosis of lymph node related diseases.