Preparation of Targeted Gd~(3+) Contrast Agent Based on Folate-receptor and Its Relaxation

OBJECTIVE To prepare the complexes of folate-chitosan-(Gd-DTPA)n ——a novel kind of folate-receptor-targeted macromolecular MRI contrast agents,and to evaluate their relaxation in vitro.METHODS Catalyzed by EDC at pH6.5,chitosan was reacted with DTPA to form chitosan-DTPA,then the complexes of chitosan-chitosan-(Gd-DTPA)n were obtained by chelating of GdCl3 with the product of folate-DTPA coupled with activated folate ester at pH 7~8.The in vitro spin-lattice relaxation of these Gd complexes were preliminarily investigated.RESULTS The coupling ratio of folate to chitosan was about 4,and the ratio of Gd-DTPA to chitosan was increased with the increasing of EDC.The relaxation of these complexes was about 6.2×10-3 L·mmol-1·ms-1,that′s about 2.3 times as the small molecular Gd-DTPA complex.CONCLUSION The MRI contrast agents mediated by folate had been prepared successfully and had high relaxation.