Rapid Self-Healing and Thixotropic Organogelation of Amphiphilic Oleanolic Acid–Spermine Conjugates,Langmuir

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Rapid Self-Healing and Thixotropic Organogelation of Amphiphilic Oleanolic Acid–Spermine Conjugates
Langmuir ( IF 3.7 ) Pub Date : 2021-02-17 , DOI: 10.1021/acs.langmuir.0c03335
Zulal Özdemir _{1,

2} , David Šaman ₃ , Kia Bertula ₄ , Manu Lahtinen ₅ , Lucie Bednárová ₃ , Markéta Pazderková _{3,

6} , Lucie Rárová ₇ , Nonappa _{4,

8} , Zdeněk Wimmer _{1,

2}

Affiliation

Natural and abundant plant triterpenoids are attractive starting materials for the synthesis of conformationally rigid and chiral building blocks for functional soft materials. Here, we report the rational design of three oleanolic acid–triazole–spermine conjugates, containing either one or two spermine units in the target molecules, using the Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction. The resulting amphiphile-like molecules 2 and 3, bearing just one spermine unit in the respective molecules, self-assemble into highly entangled fibrous networks leading to gelation at a concentration as low as 0.5% in alcoholic solvents. Using step-strain rheological measurements, we show rapid self-recovery (up to 96% of the initial storage modulus) and sol ⇔ gel transition under several cycles. Interestingly, rheological flow curves reveal the thixotropic behavior of the gels. To the best of our knowledge, this kind of behavior was not shown in the literature before, neither for a triterpenoid nor for its derivatives. Conjugate 4, having a bolaamphiphile-like structure, was found to be a nongelator. Our results indicate that the position and number of spermine units alter the gelation properties, gel strength, and their self-assembly behavior. Preliminary cytotoxicity studies of the target compounds 2–4 in four human cancer cell lines suggest that the position and number of spermine units affect the biological activity. Our results also encourage exploring other triterpenoids and their derivatives as sustainable, renewable, and biologically active building blocks for multifunctional soft organic nanomaterials.

中文翻译：

两亲齐墩果酸-精胺结合物的快速自愈和触变有机胶凝

天然和丰富的植物三萜是有吸引力的起始原料，用于合成功能性软材料的构象刚性和手性结构单元。在这里，我们报告了使用铜（I）催化的Huisgen 1,3-偶极环加成反应对目标分子中包含一个或两个精胺单元的三种齐墩果酸-三唑-精胺结合物的合理设计。生成的两亲性分子2和3，在各自的分子中仅带有一个精胺单元的分子，自组装成高度纠缠的纤维网络，导致在酒精溶剂中的凝胶化浓度低至0.5％。使用分步应变流变学测量，我们显示了快速自我恢复（高达初始储能模量的96％）和在几个循环中的sol凝胶转变。有趣的是，流变流动曲线揭示了凝胶的触变性。据我们所知，这种行为在三萜类化合物及其衍生物中都没有出现过。共轭4被发现具有类保兰两亲结构的非胶凝剂。我们的结果表明，精胺单元的位置和数量会改变胶凝特性，胶凝强度及其自组装行为。目标化合物的初步细胞毒性研究2 - 4在四种人类肿瘤细胞系表明的精胺单元的位置和数量影响生物活性。我们的结果还鼓励探索其他三萜及其衍生物，它们是多功能，柔软的有机纳米材料的可持续，可再生和具有生物活性的构建基块。

更新日期：2021-03-02

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