The UC Berkeley-UCSF Graduate Program in Bioengineering, University of California Berkeley, Berkeley, CA 94720-1762, USA.
Bioconjug Chem. 2013 Jan 16;24(1):36-43. doi: 10.1021/bc300346h. Epub 2012 Dec 18.
We report the synthesis and characterization of a series of ionizable lysine-based lipids (ILL), novel lipids containing a lysine headgroup linked to a long-chain dialkylamine through an amide linkage at the lysine α-amine. These ILLs contain two ionizable amines and a carboxylate, and exhibit pH-dependent lipid ionization that varies with lipid structure. The synthetic scheme employed allows for the simple, orthogonal manipulation of lipids. This provides a method for the development of a compositionally diverse library with varying ionizable headgroups, tail structures, and linker regions. A focused library of four ILLs was synthesized to determine the impact of hydrophobic fluidity, lipid net charge, and lipid pK(a) on the biophysical and siRNA transfection characteristics of this new class of lipids. We found that manipulation of lipid structure impacts the protonation behavior, electrostatically driven membrane disruption, and ability to promote siRNA mediated knockdown in vitro. ILL-siRNA liposomal formulations were tested in a murine Factor VII model; however, no significant siRNA-mediated knockdown was observed. These results indicate that ILL may be useful in vitro transfection reagents, but further optimization of this new class of lipids is required to develop an effective in vivo siRNA delivery system.
我们报告了一系列可离子化赖氨酸脂质（ILL）的合成和表征，这些新型脂质含有赖氨酸头基，通过赖氨酸的α-氨基上的酰胺键连接到长链二烷基胺上。这些 ILL 含有两个可离子化的胺和一个羧酸盐，表现出随脂质结构变化的 pH 依赖性脂质电离。所采用的合成方案允许对脂质进行简单的、正交的操作。这为开发具有不同可离子化头基、尾结构和连接区的组成多样的文库提供了一种方法。合成了一个包含四个 ILL 的重点文库，以确定疏水性流动性、脂质净电荷和脂质 pKa 对这一新类脂质的生物物理和 siRNA 转染特性的影响。我们发现，脂质结构的操纵会影响质子化行为、静电驱动的膜破坏以及促进体外 siRNA 介导的敲低的能力。ILL-siRNA 脂质体制剂在小鼠因子 VII 模型中进行了测试；然而，没有观察到明显的 siRNA 介导的敲低。这些结果表明，ILL 可能是有用的体外转染试剂，但需要进一步优化这一新类脂质，以开发有效的体内 siRNA 递送系统。
