Tamaki Mamiko, Fukushima Daichi, Kojima Chie
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University 1-1 Gakuen-cho, Naka-ku Sakai Osaka 599-8531 Japan
RSC Adv. 2018 Aug 6;8(49):28147-28151. doi: 10.1039/c8ra05381b. eCollection 2018 Aug 2.
Dendrimers are unique polymers with well-defined structures, and are useful as functional unimolecular nanoparticles. Previous reports have shown that polyamidoamine (PAMAM) dendrimers modified with hydrophobic molecules, such as amino-terminal phenylalanine (Phe), are thermosensitive at high pH. In the present study, we designed carboxyl-terminal Phe-modified PAMAM dendrimers that are thermosensitive under acidic conditions. We reacted an amino-terminal PAMAM dendrimer with various acid anhydrides, such as succinic anhydride, cyclohexanedicarboxylic anhydride, and phthalic anhydride, prior to the reaction with Phe. Interestingly, the amino-terminal Phe-modified PAMAM dendrimers exhibited LCST (lower critical solution temperature)-type thermosensitivity at approximately pH 7, but the carboxyl-terminal Phe-modified dendrimers exhibited UCST (upper critical solution temperature)-type thermosensitivity in acidic solutions. Temperature sensitivity was dependent on both pH and the anhydride modifier. We were able to separate rose bengal (a model compound) from aqueous solutions of the carboxyl-terminal Phe-modified dendrimer at low pH.
树枝状聚合物是具有明确结构的独特聚合物，可用作功能性单分子纳米颗粒。先前的报道表明，用疏水分子如氨基末端苯丙氨酸（Phe）修饰的聚酰胺胺（PAMAM）树枝状聚合物在高pH下具有热敏性。在本研究中，我们设计了在酸性条件下具有热敏性的羧基末端Phe修饰的PAMAM树枝状聚合物。在与Phe反应之前，我们使氨基末端PAMAM树枝状聚合物与各种酸酐（如琥珀酸酐、环己烷二甲酸酐和邻苯二甲酸酐）反应。有趣的是，氨基末端Phe修饰的PAMAM树枝状聚合物在约pH 7时表现出低临界溶液温度（LCST）型热敏性，但羧基末端Phe修饰的树枝状聚合物在酸性溶液中表现出高临界溶液温度（UCST）型热敏性。温度敏感性取决于pH和酸酐改性剂。我们能够在低pH下从羧基末端Phe修饰的树枝状聚合物的水溶液中分离出孟加拉玫瑰红（一种模型化合物）。
