Salord J, Tarnus C, Muller C D, Schuber F
Biochim Biophys Acta. 1986 Apr 8;886(1):64-75. doi: 10.1016/0167-4889(86)90212-0.
We have tested the feasibility of targeting liposomes via interaction with specific ecto-enzymes, i.e., enzymes which have their active site oriented to the external surface of the cell. 3,4-Dimethylpyridine adenine dinucleotide, a competitive inhibitor of ecto-NAD+-glycohydrolase, was substituted at N6 with a hydrophilic spacer arm, functionalized with a sulfhydryl group, and covalently linked to performed liposomes containing 4-(p-maleimidophenyl)butyryl phosphatidylethanolamine. We show that compared to control vesicles, the binding of the conjugated liposomes was greatly increased (up to 5-fold) to cells presenting ecto-NAD+-glycohydrolase activity (Swiss 3T3 fibroblasts, mouse peritoneal macrophages); in contrast, no specific binding was detected with hepatoma tissue culture cells, which lack this enzyme. Specific binding was found to depend on the ligand/lipid molar ratio of the vesicles and on the length of the arm. High concentrations of free 3,4-dimethylpyridine adenine dinucleotide virtually abolished the specific binding to cells of the targeted liposomes. Analysis of binding revealed that the ligand conjugated to the liposomes presented a functional affinity for 3T3 fibroblasts 15-fold superior to that of the free ligand.
我们已经通过与特定的胞外酶（即活性位点朝向细胞外表面的酶）相互作用来测试靶向脂质体的可行性。3,4-二甲基吡啶腺嘌呤二核苷酸是胞外NAD⁺-糖水解酶的竞争性抑制剂，在N6处被一个亲水性间隔臂取代，该间隔臂用巯基官能化，并与含有4-(对马来酰亚胺苯基)丁酰磷脂酰乙醇胺的预制脂质体共价连接。我们发现，与对照囊泡相比，共轭脂质体与具有胞外NAD⁺-糖水解酶活性的细胞（瑞士3T3成纤维细胞、小鼠腹腔巨噬细胞）的结合大大增加（高达5倍）；相反，在缺乏这种酶的肝癌组织培养细胞中未检测到特异性结合。发现特异性结合取决于囊泡的配体/脂质摩尔比和臂的长度。高浓度的游离3,4-二甲基吡啶腺嘌呤二核苷酸几乎消除了靶向脂质体与细胞的特异性结合。结合分析表明，与脂质体共轭的配体对3T3成纤维细胞的功能亲和力比游离配体高15倍。
