Langmuir. 2019 Apr 2;35(13):4646-4659. doi: 10.1021/acs.langmuir.8b04303. Epub 2019 Mar 19.
A series of anionic, zwitterionic, and cationic lysine-based block copolymers with a thermoresponsive segment were synthesized by the reversible addition-fragmentation chain transfer (RAFT) polymerization of N-acryloyl- N-carbobenzoxy-l-lysine [A-Lys(Cbz)-OH], which contains a carboxylic acid and a protected amine-functionality in the monomer unit. Carboxylic acid-containing homopolymers, poly(A-Lys(Cbz)-OH), with predetermined molecular weights with relatively low polydispersities were initially synthesized by RAFT polymerization of A-Lys(Cbz)-OH. The chain extension of the dithiocarbamate-terminated poly(A-Lys(Cbz)-OH) to N-isopropylacrylamide (NIPAM) via the RAFT process and subsequent deprotection afforded the zwitterionic block copolymer composed of thermoresponsive poly(NIPAM) and poly(A-Lys-OH), which exhibited switchability among the zwitterionic, anionic, and cationic states by pH change. The assembled structures and thermoresponsive and chiroptical properties of these block copolymers were evaluated by dynamic light scattering, circular dichroism, and turbidity measurements. Finally, the cationic block copolymer, poly(A-Lys-OMe)- b-poly(NIPAM), was obtained by the methylation of the carboxylic acid group in the zwitterionic poly(A-Lys-OH) segment. Selective interactions of DNA with the cationic poly(A-Lys-OMe) segment in the lysine-based block copolymer were further evaluated by agarose gel electrophoresis and atomic force microscopy measurements, which revealed characteristic assembled structures and temperature-responsive properties of the polyplexes.
一系列的阴离子型、两性离子型和阳离子型赖氨酸基嵌段共聚物，具有热敏性段，是通过可逆加成-断裂链转移（RAFT）聚合 N-丙烯酰基-N-碳芐氧-L-赖氨酸[A-Lys（Cbz）-OH]合成的，该单体单元中含有羧酸和保护的胺官能团。首先通过 RAFT 聚合 A-Lys（Cbz）-OH 合成了具有预定分子量和相对低的多分散性的羧酸封端均聚物，聚（A-Lys（Cbz）-OH）。通过 RAFT 过程将二硫代氨基甲酸盐封端的聚（A-Lys（Cbz）-OH）扩展到 N-异丙基丙烯酰胺（NIPAM），并随后进行脱保护，得到了由热敏性聚（NIPAM）和聚（A-Lys-OH）组成的两性离子嵌段共聚物，通过 pH 值变化可以在两性离子、阴离子和阳离子状态之间进行切换。通过动态光散射、圆二色性和浊度测量评估了这些嵌段共聚物的组装结构以及热响应和手性光学性质。最后，通过两性离子聚（A-Lys-OH）段中羧酸基团的甲基化得到了阳离子嵌段共聚物，聚（A-Lys-Ome）-b-聚（NIPAM）。通过琼脂糖凝胶电泳和原子力显微镜测量进一步评估了 DNA 与赖氨酸基嵌段共聚物中阳离子聚（A-Lys-Ome）段之间的选择性相互作用，这揭示了聚电解质复合物的特征组装结构和温度响应性质。
