Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands.
J Control Release. 2011 Dec 20;156(3):307-14. doi: 10.1016/j.jconrel.2011.07.023. Epub 2011 Jul 22.
The adsorption of blood proteins onto liposomes and other colloidal particles is an important process influencing the circulation time. Proteins adsorbed to the surface of liposomes can mediate recognition of the liposomes by macrophages of the reticuloendothelial system (RES) facilitating their clearance from the circulation. Coating liposomes with poly(ethylene glycol) (PEG) decreases the blood clearance considerably, most likely due to reduced protein adsorption and/or liposome aggregation. By using the relation between clearance and protein binding, the present study introduces an in vitro assay measuring interactions of liposomes with proteins to predict their blood clearance in vivo. Such assay is valuable since it limits time and costs, and importantly reduces the number of animals required for pharmacokinetic investigations of new formulations. In the current study, Surface Plasmon Resonance (SPR) and fluorescence Single Particle Tracking (fSPT) were used to study liposome-protein interactions and blood induced liposome aggregation in vitro. By means of SPR the interactions between proteins and liposomes coated with PEG of different molecular weights and at different densities (PEG(2000) in 2.5%, 5% and 7%; PEG(5000) in 0.5%, 1.5% and 2.5%), were measured for several plasma proteins: human serum albumin (HSA), apolipoprotein E (ApoE), α2-macroglobulin (α2-M), β2-glycoprotein (β2-G) and fibronectin (Fn). Liposomes coated with PEG interacted less with all proteins, an effect which increased with the PEG surface density. In parallel, fSPT analysis showed that the exposure of liposomes to full blood did not change the liposome size, indicating that aggregation is not a strong attributive factor in the clearance of these liposomes. In addition, the SPR measurements of the interactions between liposomes and proteins were correlated with the blood clearance of the liposomes. For each protein, the degree of protein-liposome interaction as determined by SPR showed a moderate to strong positive correlation with the clearance of the liposome type.
蛋白质吸附到脂质体和其他胶体颗粒上是影响循环时间的重要过程。吸附在脂质体表面的蛋白质可以介导巨噬细胞对网状内皮系统 (RES) 中脂质体的识别，从而促进其从循环中清除。用聚乙二醇 (PEG) 对脂质体进行涂层处理会大大降低血液清除率，这很可能是由于蛋白质吸附和/或脂质体聚集减少所致。通过利用清除率与蛋白质结合之间的关系，本研究提出了一种体外测定方法，用于测量脂质体与蛋白质的相互作用，以预测其在体内的血液清除率。这种测定方法具有重要的价值，因为它可以限制时间和成本，并且重要的是，它可以减少新制剂药代动力学研究所需的动物数量。在本研究中，表面等离子体共振 (SPR) 和荧光单粒子跟踪 (fSPT) 用于研究体外脂质体-蛋白质相互作用和血液诱导的脂质体聚集。通过 SPR 测量了不同分子量和不同密度的 PEG（2.000 时为 2.5%、5%和 7%；5.000 时为 0.5%、1.5%和 2.5%）涂层的脂质体与几种血浆蛋白（人血清白蛋白 (HSA)、载脂蛋白 E (ApoE)、α2-巨球蛋白 (α2-M)、β2-糖蛋白 (β2-G) 和纤维连接蛋白 (Fn)) 之间的相互作用。用 PEG 涂层处理的脂质体与所有蛋白质的相互作用都较少，这种效应随 PEG 表面密度的增加而增加。同时，fSPT 分析表明，将脂质体暴露于全血中不会改变脂质体的大小，这表明聚集不是这些脂质体清除的主要归因因素。此外，脂质体与蛋白质之间相互作用的 SPR 测量结果与脂质体的血液清除率相关。对于每种蛋白质，SPR 测定的蛋白质-脂质体相互作用程度与脂质体类型的清除率呈中度至强正相关。
