Issue 7, 2013

Polymer cross-linking: a nanogel approach to enhancing the relaxivity of MRI contrast agents

Abstract

Polymer cross-linking was explored as an approach for increasing the relaxivity of macromolecular contrast agents for magnetic resonance imaging. Poly(ethylene glycol) methyl ether methacrylate, N-(2-aminoethyl)methacrylamide hydrochloride, and the cross-linker ethylene glycol dimethacrylate were copolymerized under free radical conditions. By tuning the cross-linker content and reaction concentration, it was possible to obtain 10 nm nanogels in a single synthetic step. The pendant amine moieties were functionalized with an isothiocyanate derivative of diethylenetriaminepentaacetic acid (DTPA) and Gd(III) was chelated. In comparison with a linear control polymer prepared under the same conditions in the absence of the cross-linking agent, the nanogel contrast agent did exhibit enhanced relaxivity with an r1 of 20.8 ± 0.2 at 20 MHz and 17.5 ± 0.4 at 60 MHz (corresponding to the clinical field strength of 1.5 T). The nuclear magnetic resonance dispersion profile was modeled to demonstrate that the enhanced relaxivity was a result of the nanogel agent's increased rotational correlation time, that is proposed to result from the constraint on motion imparted by the cross-linking. T1 weighted imaging in mice showed enhanced contrast and vascular circulation for the nanogel relative to Gd(III)–DTPA (Magnevist) demonstrating the future promise of these new agents.

Graphical abstract: Polymer cross-linking: a nanogel approach to enhancing the relaxivity of MRI contrast agents

Supplementary files

Article information

Article type
Paper
Submitted
02 Nov 2012
Accepted
06 Dec 2012
First published
07 Dec 2012

J. Mater. Chem. B, 2013,1, 1027-1034

Polymer cross-linking: a nanogel approach to enhancing the relaxivity of MRI contrast agents

A. Soleimani, F. Martínez, V. Economopoulos, P. J. Foster, T. J. Scholl and E. R. Gillies, J. Mater. Chem. B, 2013, 1, 1027 DOI: 10.1039/C2TB00352J

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