Tilcock C, Ahkong Q F, Koenig S H, Brown R D, Kabalka G, Fisher D
Department of Radiology, University of British Columbia, Vancouver, Canada.
Biochim Biophys Acta. 1992 Oct 5;1110(2):193-8. doi: 10.1016/0005-2736(92)90358-s.
Covalent attachment of methoxypoly(ethylene glycol) (MPEG) 5000 to the surface of unilamellar liposomes composed of egg phosphatidylcholine and dioleoylphosphatidylethanolamine (DOPE) (8:2) containing paramagnetic chelates, either entrapped within the interior volume of the liposomes, or associated with the membrane surface, had no effect upon the measured spin-lattice relaxation rates (1/T1) for water in these systems. 31P-NMR studies indicate no destabilization of dioleoylphosphatidylcholine (DOPC)/(DOPE) (1:1) vesicles following attachment of MPEG. However, in DOPC/DOPE (1:3) mixtures, covalent modification with MPEG results in a destabilization of multilamellar vesicles into smaller vesicular structures. These results indicate that covalent attachment of poly(ethylene glycol) to liposomal magnetic resonance agents may prove a useful method for increasing their utility as vascular MR agents by extending their lifetime in the circulation, without decreasing the relaxivity of paramagnetic species associated with the liposome, but that the presence of PEG covalently attached to the membrane surface may modify the polymorphic phase behavior of the lipid system to which it is covalently linked.
将甲氧基聚乙二醇（MPEG）5000共价连接到由鸡蛋磷脂酰胆碱和二油酰磷脂酰乙醇胺（DOPE）（8:2）组成的单层脂质体表面，这些脂质体含有顺磁性螯合物，它们要么包裹在脂质体内部，要么与膜表面结合，对这些体系中测得的水的自旋晶格弛豫率（1/T1）没有影响。31P-NMR研究表明，MPEG连接后，二油酰磷脂酰胆碱（DOPC）/（DOPE）（1:1）囊泡没有失稳。然而，在DOPC/DOPE（1:3）混合物中，MPEG的共价修饰导致多层囊泡失稳形成较小的囊泡结构。这些结果表明，将聚乙二醇共价连接到脂质体磁共振剂上，可能是一种有用的方法，通过延长其在循环中的寿命来提高其作为血管磁共振剂的效用，而不会降低与脂质体相关的顺磁性物质的弛豫率，但共价连接到膜表面的PEG的存在可能会改变与其共价连接的脂质体系的多晶型相行为。
