Institut of Pharmaceutical Sciences, ETH Zurich, 8093 Zurich, Switzerland.
Biointerphases. 2006 Dec;1(4):123-33. doi: 10.1116/1.2409645.
Microparticulate carrier systems have significant potential for antigen delivery. The authors studied how microspheres coated with the polycationic copolymer poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) can be protected against unspecific phagocytosis by antigen presenting cells, a prerequisite for selective targeting of phagocytic receptors. For this aim the authors explored the influence of PLL-g-PEG architecture on recognition of coated microspheres by antigen presenting cells with regard to both grafting ratio and molecular weight of the grafted PEG chains. Carboxylated polystyrene microspheres (5 microm) were coated with a small library of PLL-g-PEG polymers with PLL backbones of 20 kDa, grafting ratios from 2 to 20, and PEG side chains of 1-5 kDa. The coated microspheres were characterized by their zeta-potential and resistance to IgG adsorption. Phagocytosis of these microspheres by human monocyte derived dendritic cells (DCs) and macrophages (MPhi) was quantified by phase contrast microscopy and by analysis of the cells' side scattering in a flow cytometer. Generally, increasing grafting ratios impaired the protein resistance of coated microspheres, leading to higher phagocytosis rates. For DC, long PEG chains of 5 kDa decreased the phagocytosis of coated microspheres even in the case of considerable IgG adsorption. In addition, preferential adsorption of dysopsonins is discussed as another factor for decreased phagocytosis rates. For comparison, the authors studied the cellular adhesion of DC and MPhi to PLL-g-PEG coated microscopy slides. Remarkably, DC and MPhi were found to adhere to relatively protein-resistant PLL-g-PEG adlayers, whereas phagocytosis of microspheres coated with the same copolymers was inefficient. Overall, PLL(20)-[3.5]-PEG(2) was identified as the optimal copolymer to ensure resistance to both phagocytosis and cell adhesion. Finally, the authors studied coatings made from binary mixtures of PLL-g-PEG type copolymers that led to microspheres with combined properties. This enables future studies on cell targeting with ligand modified copolymers.
微粒载体系统在抗原递送上具有很大的潜力。作者研究了如何通过将带正电荷的共聚物聚（L-赖氨酸）-接枝-聚（乙二醇）（PLL-g-PEG）涂覆微球来保护其免受抗原呈递细胞的非特异性吞噬，这是吞噬受体选择性靶向的前提。为此，作者研究了 PLL-g-PEG 结构对带正电荷的微球被抗原呈递细胞识别的影响，包括接枝比和接枝 PEG 链的分子量。用一小部分具有 20 kDa PLL 主链、2 至 20 的接枝比和 1 至 5 kDa 的 PEG 侧链的 PLL-g-PEG 聚合物涂覆 5 µm 的羧化聚苯乙烯微球。通过 Zeta 电位和抗 IgG 吸附性对涂覆的微球进行了表征。通过相差显微镜和流式细胞仪分析细胞侧向散射来定量这些微球被人单核细胞衍生的树突状细胞 (DC) 和巨噬细胞 (MPhi) 的吞噬作用。一般来说，增加接枝比会降低涂覆微球的蛋白质抗性，从而导致更高的吞噬率。对于 DC，即使 IgG 吸附量相当大，长 5 kDa 的 PEG 链也会降低涂覆微球的吞噬率。此外，还讨论了作为降低吞噬率的另一个因素的非调理素的优先吸附。作为比较，作者研究了 DC 和 MPhi 对涂覆有 PLL-g-PEG 的显微镜载玻片的细胞黏附作用。值得注意的是，发现 DC 和 MPhi 能够黏附到相对蛋白质抗性的 PLL-g-PEG 吸附层上，而用相同共聚物涂覆的微球的吞噬作用效率较低。总体而言，PLL(20)-[3.5]-PEG(2)被确定为确保对吞噬作用和细胞黏附都具有抗性的最佳共聚物。最后，作者研究了由 PLL-g-PEG 型共聚物的二元混合物制成的涂层，这些涂层使微球具有组合性能。这为使用配体修饰共聚物进行细胞靶向研究提供了基础。
