PAMAM dendrimeric conjugates with a Gd-DOTA phosphinate derivative and their adducts with polyaminoacids: The interplay of global motion, internal rotation, and fast water exchange
PAMAM dendrimeric conjugates with a Gd-DOTA phosphinate derivative and their adducts with polyaminoacids: The interplay of global motion, internal rotation, and fast water exchange
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DOI：
10.1021/bc060149l
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发表时间：
2006-07-19
影响因子：
4.7
通讯作者：
Aime, Silvio
中科院分区：
文献类型：
--
作者：
Rudovsky, Jakub;Botta, Mauro;Aime, Silvio
制备了一系列以PAMAM（聚氨基胺）为骨架，配以大环Gd-DO3A-P-ABn配合物（DOTA的单磷酸类似物）的树状分子缀合物。螯合物通过硫脲连接物以高负载（> 90%）共价附着在G1-、G2-和G4-PAMAM树状大分子上。制备的偶联物G1-(Gd- DO3A-P-BnN{CS})(8)、G2-(Gd-DO3A-P-BnN{CS})（16）和G4-(Gd-DO3A-P-BnN{CS})（59）在20 MHz、37℃、pH值7.5下的弛豫度分别为10.1、14.1和18.6 s(-1) mM（-1）。一项变pH研究（范围2-12）表明，G2-(Gd-DO3A-P-BnN{CS})（16）共轭物在低pH下的弛豫度增加了30%。未经修饰的G2树状大分子的H-1核磁共振滴定证实，这是由于核心叔胺的质子化导致更开放和刚性的结构。温度变化的O-17核磁共振和H-1核磁共振弛豫研究证实，弛豫不是由水交换控制，而是由旋转动力学控制。利用Lipari-Szabo方法进行的多参数数据评估显示，所研究的共轭物在水中的停留寿命（298）tau(M)约为45-70 ns，比单体模型化合物Gd-DO3A-PABn的停留寿命（16 ns）长，但足够短，不会限制其弛性。全球旋转相关时间（298）tau（Rg）在1.5 - 3.1 ns之间变化，似乎表明分子翻滚速度足够慢，可以实现测量到的高弛豫度；然而，描述内部柔韧性的刚度因子S-2（类似于0.26）远非最佳。当带正电的聚氨基酸如聚（Arg）或聚（Lys）加入到共轭溶液中时，总弛豫度显著增加(例如，G1-（Gd-DO3A-P-BnN{CS})(8)共轭物的弛豫度增加了1.8倍）。静电相互作用部分“冻结”了共轭物的内部迁移率，也减缓了整体运动。G2-(Gd-DO3A-P-BnN{CS})(16)-poly(Lys) 59加合物的1H弛豫数据证实了这一假设。重要的是，证明了加合物的形成不会阻碍水交换过程。
A series of dendrimeric conjugates based on a PAMAM (polyamidoamine) backbone with macrocyclic Gd-DO3A-P-ABn complexes (monophosphinated analogue of DOTA) was prepared. The chelates were covalently attached to the G1-, G2-, and G4-PAMAM dendrimers through a thiourea linker in high loads (> 90%). The prepared conjugates G1-(Gd- DO3A-P-BnN{CS})(8), G2-(Gd-DO3A-P-BnN{CS})(16), and G4-(Gd-DO3A-P-BnN{CS})(59) showed relaxivities of 10.1, 14.1, and 18.6 s(-1) mM(-1) at 20 MHz and 37 degrees C and pH) 7.5, respectively. A variable-pH study (range 2-12) revealed up to 30% increase in the relaxivity at low pH for the G2-(Gd-DO3A-P-BnN{CS})(16) conjugate. As confirmed by H-1 NMR titration of the unmodified G2 dendrimer, this is due to protonation of core tertiary amines leading to a more open and rigid structure. The variable-temperature O-17 NMR and H-1 NMRD relaxometric studies confirmed that the relaxivity is not controlled by water exchange but by rotational dynamics. A multiparametrical data evaluation using the Lipari-Szabo approach revealed that the water residence lifetime, (298)tau(M), for the conjugates studied was ca. 45-70 ns, which is longer than the value found for the monomeric model compound Gd-DO3A-PABn (16 ns) but short enough so as not to limit the relaxivity. The global rotational correlation time, (298)tau(Rg), varied from 1.5 to 3.1 ns and seemed to indicate a sufficiently slow molecular tumbling to achieve the high relaxivities measured; however, the rigidity factor S-2 (similar to 0.26), describing the internal flexibility, was far from optimum. The overall relaxivity was significantly increased (e.g. by a factor of 1.8 for the G1-(Gd-DO3A-P-BnN{CS})(8) conjugate) when a positively charged polyaminoacid like poly(Arg) or poly(Lys) was added to the conjugate solutions. The electrostatic interactions partially "freeze" the internal mobility of the conjugate and also slow down global motion. This assumption was confirmed by an evaluation of 1H relaxometric data obtained for the G2-(Gd-DO3A-P-BnN{CS})(16)-poly(Lys) 59 adduct. Importantly, it was proved that the adduct formation did not hamper the water exchange process.