PEGylated Polyethylenimine as Enhanced T-1 Contrast Agent for Efficient Magnetic Resonance Imaging

Currently used small molecular magnetic resonance (MR) imaging contrast agents (CM) in clinics have relatively short half-lives, which has limited the acquisition of high-resolution organ and angiographic images. Therefore, development of a facile strategy for the synthesis of long-circulating CAs with the transforming potential for MR imaging still remains a great challenge. Here we communicate the design and synthesis of PEGylated polyethylenimine (PEI) and its application as enhanced T-1 CA for the long-circulating blood pool as well as efficient organ and tumor imaging. In this study, PEI was covalently grafted with gadolinium (Gd-III) chelator and mPEGNHS, followed by acetylation of the remaining amines to improve biocompatibility and prolong circulation time. With the relatively long circulation time (3.8 h), the formed multifunctional PEI (PEI.NHAc-DTPA(Gd-III)-mPEG) can be used as an enhanced T-1 CA for blood pool and major organ imaging, and could be cleared from the body 96 h post administration through the urinary system. Importantly, the PEI.NHAc-DTPA(Gd-III)-mPEG complexes displayed a strong T-1 contrast effect for tumor imaging through the enhanced permeation and retention effect. These findings suggest that the synthesized PEI.NHAc-DTPA(Gd-III)-mPEG may be used as a promising CA for T-1 MR imaging of various biological systems.

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