二级生物响应性脂质基因输送系统设计、构效关系及体内效果评价

In the purpose of improving two major problems including toxicity and low transfection efficiency in vivo, for cationic lipid gene vector system, a series of dual bioresponsive lipidic gene delivery carriers have been constructed. Cationic lipid with peptides dendron as cationic head, different length of aliphatic chain as hydrophobic tail were synthesized. Reduction sensitive disulfide (or diselenide) bond was used to conjugate the head and tail of cationic lipid, pH-sensitive binding (or enzyme-sensitive peptide) was applied to the connection between cholesterol and the hydrophilic PEG (or hyaluronic acid, HA). PEG (or HA) performance as the shielding of the system, in the aims of achieving long circulation; through the EPR effect (or modified ligands on PEG / HA), nano-sized carriers in the low pH conditions (tumor or lysosomes) occurred the first bioresponse to deshield of PEG or HA; when the vector / gene complexes were released into the cytoplasm, the reductive conditions triggered the second bioresponse that inducing carrier degradation and disassociation with gene. Through a comprehensive study of the system, structure-activity relationship of lipid carrier, the process and mechanism of endocytosis of the cationic lipid gene vector, in vivo effect of transfection should be well clarified, which will be benefit for the lipid carrier design and further gene therapy in vivo.

本项目针对阳离子脂质基因载体系统研究中面临的毒性大、体内转染效率低两大问题，设计构建一系列以肽类树状大分子为阳离子头部、不同长度脂肪链为疏水尾部的阳离子脂质载体，并以还原敏感的二硫键（或二硒键）键合阳离子脂质头尾部，pH敏感键（或酶敏感短肽）连接胆固醇与亲水性PEG（或透明质酸，HA）部分，形成二级生物响应的脂质基因输送载体，研究其体内基因转染效果。该系统可利用PEG（或HA）的屏蔽达到长循环；通过EPR效应（或PEG上修饰的配体/或HA）到达肿瘤组织；在低pH条件下（肿瘤部位或溶酶体中）纳米载体的屏蔽层（PEG或HA）发生一级生物响应而剥离；当载体/基因复合物被释放到细胞浆后，还原性的条件诱发第二级生物响应，载体降解并释放基因。通过对该系统的全面考察，可对脂质载体的构效关系、阳离子脂质基因载体系统入胞过程和机理进行研究，评价其体内转染效果，为脂质载体设计和基因的体内评价提供研究数据。

本项目针对阳离子脂质基因载体系统研究中面临的毒性大、体内转染效率低两大问题，设计构建一系列以肽类树状大分子为阳离子头部、不同长度脂肪链为疏水尾部的阳离子脂质载体，并以不同敏感度的还原敏感的二硫键、二硒键 或柠康酐、琥珀酸酐修饰基因载体的不同组成部份，形成二级生物响应的脂质基因输送载体，研究其体内基因转染效果。该系统可利用HA或负电荷的屏蔽达到长循环；通过EPR效应到达肿瘤组织；在pH6.8或高GSH条件下（肿瘤部位或溶酶体中）纳米载体的屏蔽层发生一级生物响应而剥离或电荷翻转；当载体/基因复合物被释放到细胞浆或溶酶体后，还原性的条件或更低的pH5.5条件诱发第二级生物响应，载体降解并释放基因。通过对该系统的全面考察，可对脂质载体的构效关系、阳离子脂质基因载体系统入胞过程和机理进行研究，评价其体内转染效果，为脂质载体设计和基因的体内评价提供研究数据。