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A polymeric micelle MRI contrast agent with changeable relaxivity.

Nakamura E, Makino K, Okano T, Yamamoto T, Yokoyama M

Tokyo University of Science, Department of Pharmaceutics, 2641 Yamasaki, Noda, Chiba 278-8510, Japan.

Polymeric micelles were formed from cationic polymers (polyallylamine or protamine) and anionic block copolymers (poly(ethylene glycol)-b-poly(aspartic acid) derivative) that bound Gd ions providing high contrasts in Magnetic Resonance Imaging (MRI) by shortening the T(1) longitudinal relaxation time of protons of water. The Gd-binding block copolymer alone showed high relaxivity (T(1)-shortening ability) values from 10 to 11 mol(-1) s(-1), while the polymeric micelles exhibited low relaxivity values from 2.1 to 3.6 mol(-1) s(-1). These findings point to the feasibility of a novel MRI contrast agent that selectively provides high contrasts at solid tumor sites owing to a dissociation of the micelle structures, while selective delivery to the tumor sites is achieved in the polymeric micelle form.

Published 8 September 2006 in J Control Release, 114(3): 325-33.
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