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.