Bioconjug Chem. 2013 Aug 21;24(8):1332-44. doi: 10.1021/bc400011v.
Novel PEGtide dendrons of generations 1 through 5 (G1.0–5.0) containing alternating discrete poly(ethylene glycol) (dPEG) and amino acid/peptide moieties were designed and developed. To demonstrate their targeting utility as nanocarriers, PEGtide dendrons functionalized with mannose residues were developed and evaluated for macrophage targeting. PEGtide dendrons were synthesized using 9-fluorenylmethyloxycarbonyl (Fmoc) solid-phase peptide synthesis (SPPS) protocols. The N-α-Fmoc-N-ε-(5-carboxyfluorescein)-l-lysine (Fmoc-Lys(5-FAM)-OH) and monodisperse Fmoc-dPEG6-OH were sequentially coupled to Fmoc-β-Ala-resin to obtain the resin-bound intermediate Fmoc-dPEG6-Lys(5-FAM)-β-Ala (1). G1.0 dendrons were obtained by sequentially coupling Fmoc-Lys(Fmoc)-OH, Fmoc-β-Ala-OH, and Fmoc-dPEG6-OH to 1. Dendrons of higher generation, G2.0–5.0, were obtained by repeating the coupling cycles used for the synthesis of G1.0. Dendrons containing eight mannose residues (G3.0-mannose8) were developed for mannose receptor (MR) mediated macrophage targeting by conjugating α-d-mannopyranosylphenyl isothiocyanate to G3.0 dendrons. In the present study PEGtide dendrons up to G5.0 were synthesized. The molecular weights of the dendrons determined by MALDI-TOF were in agreement with calculated values. The hydrodynamic diameters measured using dynamic light scattering (DLS) ranged from 1 to 8 nm. Cell viability in the presence of G3.0 and G3.0-mannose8 was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and was found to be statistically indistinguishable from that of untreated cells. G3.0-mannose8 exhibited 12-fold higher uptake than unmodified G3.0 control dendrons in MR-expressing J774.E murine macrophage-like cells. Uptake was nearly completely inhibited in the presence of 10 mg/mL mannan, a mannose analogue and known MR substrate. Confocal microscopy studies demonstrated the presence of significant intracellular punctate fluorescence colocalized with a fluid endocytosis marker with little surface fluorescence in cells incubated with G3.0-mannose8. No significant cell-associated fluorescence was observed in cells incubated with G3.0 dendrons that did not contain the targeting ligand mannose. The current studies suggest that PEGtide dendrons could be useful as nanocarriers in drug delivery and imaging applications.
设计并开发了 1 到 5 代的新型聚乙二醇（PEG）肽树突（G1.0-G5.0），其中包含交替离散的聚乙二醇（dPEG）和氨基酸/肽部分。为了证明它们作为纳米载体的靶向用途，开发了甘露糖残基功能化的 PEG 肽树突，并对其进行了巨噬细胞靶向评估。PEG 肽树突使用 9-芴甲氧羰基（Fmoc）固相肽合成（SPPS）方案合成。将 N-α-Fmoc-N-ε-（5-羧基荧光素）-l-赖氨酸（Fmoc-Lys（5-FAM）-OH）和单分散 Fmoc-dPEG6-OH 顺序偶联到 Fmoc-β-Ala-树脂上，得到树脂结合中间体 Fmoc-dPEG6-Lys（5-FAM）-β-Ala（1）。通过顺序偶联 Fmoc-Lys（Fmoc）-OH、Fmoc-β-Ala-OH 和 Fmoc-dPEG6-OH 来获得 G1.0 树突。通过重复用于 G1.0 合成的偶联循环来获得更高代的树突，G2.0-G5.0。通过将α-d-甘露吡喃糖基苯基异硫氰酸酯偶联到 G3.0 树突上来开发含八个甘露糖残基的树突（G3.0-甘露糖 8），用于甘露糖受体（MR）介导的巨噬细胞靶向。通过基质辅助激光解吸电离飞行时间质谱（MALDI-TOF）测定的树突的分子量与计算值一致。使用动态光散射（DLS）测量的水动力直径在 1 至 8nm 之间。使用 3-（4,5-二甲基噻唑-2-基）-2,5-二苯基四氮唑溴化物（MTT）测定法评估 G3.0 和 G3.0-甘露糖 8 存在时的细胞活力，发现与未经处理的细胞相比，细胞活力无统计学差异。在表达 MR 的 J774.E 鼠巨噬样细胞中，G3.0-甘露糖 8 的摄取比未修饰的 G3.0 对照树突高 12 倍。在存在 10mg/mL 甘露聚糖（甘露糖类似物和已知的 MR 底物）的情况下，摄取几乎完全被抑制。共焦显微镜研究表明，在用 G3.0-甘露糖 8 孵育的细胞中，存在与液泡内吞作用标记物高度共定位的显著细胞内点状荧光，而细胞表面荧光很少。在用不包含靶向配体甘露糖的 G3.0 树突孵育的细胞中，未观察到明显的细胞相关荧光。目前的研究表明，PEG 肽树突可用作药物输送和成像应用中的纳米载体。
