Cationic lipids have become known as one of the most versatile tools for the delivery of DNA, RNA and many other therapeutic molecules, and are especially attractive because they can be easily designed, synthesized and characterized. Most of cationic lipids share the common structure of cationic head groups and hydrophobic portions with linker bonds between both domains. The linker bond is an important determinant of the chemical stability and biodegradability of cationic lipid, and further governs its transfection efficiency and cytotoxicity. Based on the structures of linker bonds, they can be grouped into many types, such as ether, ester, amide, carbamate, disulfide, urea, acylhydrazone, phosphate, and other unusual types (carnitine, vinyl ether, ketal, glutamic acid, aspartic acid, malonic acid diamide and dihydroxybenzene). This review summarizes some research results concerning the nature (such as the structure and orientation of linker groups) and density (such as the spacing and the number of linker groups) of linker bond for improving the chemical stability, biodegradability, transfection efficiency and cytotoxicity of cationic lipid to overcome the critical barriers of in vitro and in vivo transfection.

阳离子脂质已被公认为是递送DNA ，RNA和许多其他治疗性分子的最通用工具之一，并且特别有吸引力，因为它们易于设计，合成和表征。大多数阳离子脂质具有两个结构域之间带有连接键的阳离子头基和疏水部分的共同结构。接头键是决定阳离子脂质化学稳定性和生物降解性的重要决定因素，并进一步控制其转染效率和细胞毒性。根据接头键的结构，它们可以分为许多类型，如醚，酯，酰胺，氨基甲酸酯，二硫键，尿素，酰基hydr，磷酸盐和其他异常类型（肉碱，乙烯基醚，缩酮，谷氨酸，天冬氨酸，丙二酸二酰胺和二羟基苯）。这篇综述总结了一些有关接头键的性质（例如接头基团的结构和方向）和密度（例如接头基团的间距和数目）的研究结果，以改善其化学稳定性，生物降解性，转染效率和细胞毒性。阳离子脂质可克服体外和体内转染的关键障碍。