This study investigates changes in the MRI contrast properties of Gd(III)-containing paramagnetic liposomes following the incorporation of photosensitizing agent (ZnPc—zinc phthalocyanine). It provides identification of mechanisms responsible for enhancement of proton relaxation rate and hence, the increased both r1 and r2 relaxivities. Five liposomal formulations, containing fatty acids derivatives of Gd(III) salt and hydrophobic ZnPc, were synthesized. NMRD profiles of liposomal solutions (magnetic field range from 0.0002 to 9.4 T) were obtained and Modified Florence model was applied. The contrast properties of the model drug itself was separated from the lipid bilayer deformation influence, caused by its incorporation. The latter resulted, among other, in optimization of an apparent water exchange correlation time. As Gd(III) is located in the outer and inner lipid layers, some of the Gd(III) chelates are localized in aqueous interior of the liposomes, thus their contrasting efficiency depends on the water exchange rate through the membrane. The proposed approach raises the possibility of reducing the amount of potentially harmful contrast media based on gadolinium, by taking into account the increase of the relaxation effect caused by other components of the system.

中文翻译：

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治疗剂对钆脂质体治疗药物松弛性的积极影响

本研究调查了掺入光敏剂（ZnPc-锌酞菁）后含 Gd(III) 的顺磁性脂质体的 MRI 对比度特性的变化。它提供了负责提高质子弛豫率的机制的鉴定，从而增加了 r1 和 r2 弛豫率。合成了五种脂质体制剂，其中包含 Gd(III) 盐和疏水性 ZnPc 的脂肪酸衍生物。获得了脂质体溶液（磁场范围从 0.0002 到 9.4 T）的 NMRD 谱，并应用了修正的佛罗伦萨模型。模型药物本身的对比特性与由其掺入引起的脂质双层变形影响分开。后者导致表观水交换相关时间的优化等。由于 Gd(III) 位于脂质外层和内层，一些 Gd(III) 螯合物位于脂质体的水性内部，因此它们的对比效率取决于通过膜的水交换率。通过考虑由系统的其他组件引起的松弛效应的增加，所提出的方法提高了减少基于钆的潜在有害造影剂的量的可能性。