ABSTRACT

A variety of poly(N-isopropylacrylamide) (PIPAAm)-grafted surfaces have been reported for temperature-controlled cell adhesion/detachment. However, the surfaces reported to date need further improvement to achieve good outcomes for both cell adhesion and detachment, which are inherently contradictory behaviors. This study investigated the effects of terminal cationization and length of grafted PIPAAm chains on temperature-dependent cell behavior. PIPAAm brushes with three chain lengths were constructed on glass coverslips via surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization. Terminal substitution of the grafted PIPAAm chains with either monocationic trimethylammonium or nonionic isopropyl moieties was performed through the reduction of terminal RAFT-related groups and subsequent thiol-ene reaction with the corresponding acrylamide derivatives. Although the thermoresponsive properties of the PIPAAm brush surfaces were scarcely affected by the terminal functional moiety, the zeta potentials of the cationized PIPAAm surfaces were higher than those of the nonionized ones, both below and above the phase transition temperature of PIPAAm (30°C). When bovine endothelial cells were cultured on each surface at 37°C, the number of adherent cells decreased with longer PIPAAm. Notably, cell adhesion on the cationized PIPAAm surfaces was higher than that on the nonionized surfaces. This terminal effect on cell adhesion gradually weakened with increasing PIPAAm length. In particular, long-chain PIPAAm brushes virtually showed cell repellency even at 37°C, regardless of the termini. Interestingly, moderately long-chain PIPAAm brushes promoted cell detachment at 20°C, with negligible terminal electrostatic interruption. Consequently, both cell adhesion and detachment were successfully improved by choosing an appropriate PIPAAm length with terminal cationization.

摘要

各种聚( N-异丙基丙烯酰胺) (PIPAAm) - 接枝表面已被报道用于温度控制的细胞粘附/分离。然而，迄今为止报道的表面需要进一步改进才能在细胞粘附和脱离方面取得良好的结果，这两者本质上是相互矛盾的行为。本研究调查了末端阳离子化和接枝 PIPAAm 链长度对温度依赖性细胞行为的影响。通过表面引发的可逆加成-断裂链转移 (RAFT) 聚合在玻璃盖玻片上构建具有三个链长的 PIPAAm 刷子。用单阳离子三甲基铵或非离子异丙基部分对接枝的 PIPAAm 链进行末端取代是通过末端 RAFT 相关基团的还原和随后与相应丙烯酰胺衍生物的硫醇-烯反应来进行的。尽管 PIPAAm 刷表面的热响应特性几乎不受末端官能团的影响，但阳离子化 PIPAAm 表面的 zeta 电位高于非离子化表面的 zeta 电位，低于和高于 PIPAAm 的相变温度（30°C） . 当牛内皮细胞在 37°C 的每个表面上培养时，贴壁细胞的数量随着 PIPAAm 的延长而减少。值得注意的是，阳离子化 PIPAAm 表面上的细胞粘附高于非离子化表面上的细胞粘附。这种对细胞粘附的终末效应随着 PIPAAm 长度的增加而逐渐减弱。特别是，长链 PIPAAm 刷即使在 37°C 下也几乎显示出细胞排斥性，无论末端如何。有趣的是，中等长链 PIPAAm 刷子在 20°C 下促进细胞脱离，末端静电中断可忽略不计。因此，通过选择合适的具有末端阳离子化的 PIPAAm 长度，成功地改善了细胞粘附和脱离。