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Laus, S ; Sour, A ; Ruloff, R ; Tóth, E ; Merbach, AE

Rotational Dynamics Account for pH-Dependent Relaxivities of PAMAM Dendrimeric, Gd-based Potential MRI Contrast Agents

Chemistry, A European Journal 11 3064-3076

par Administrateur - publié le

Abstract :

The EPTPA(5-) chelate, which ensures fast water exchange in Gd-III complexes, has been coupled to three different generations (5, 7, and 9) of polyamidoamine (PAMAM) dendrimers through benzylthiourea linkages (H(5)EPTPA = ethylenepropylenetriamine-N,N,N’,N",N"-pentaacetic acid). The proton relaxivities measured at pH 7.4 for the dendrimer complexes G5-(GdEPTPA)(111) G7-(GdEPTPA)(253) and G9-(GdEPTPA)(1157) decrease with increasing temperature, indicating that, for the first time for dendrimers, slow water exchange does not limit relaxivity. At a given field and temperature, the relaxivity increases from G5 to G7, and then slightly decreases for G9 (r(1) = 20.5, 28.3 and 27.9 mm(-1)s(-1), respectively, at 37 degrees C, 30 MHz).