Thermogelling behavior of aqueous polymer solutions comes from the delicate balance between hydrophilic and hydrophobic moieties of the polymer. Typically, poly(ethylene glycol) (PEG) has been used as a hydrophilic block in most thermogels reported to date. However, recent papers have suggested the potential immunogenicity of PEG-conjugated compounds. Here, we report that aqueous solutions of dl-polyalanine (DL-PA) with a specific molecular weight can exhibit thermogelling behavior. In particular, DL-PA with a molecular weight (M_n) of 6690 Da, DL-PA67, exhibited sol-to-gel transition at the physiologically important temperature range of 30–40 °C. ¹H NMR and FTIR data indicated that the mechanism of thermogelation is related to dehydration and conformational changes of DL-PA67 from random coil to β-sheet structures. Subcutaneous injection of an aqueous DL-PA67 solution into rats confirmed the gel formation and its histocompatibility with mild tissue irritation.

中文翻译：

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dl-聚丙氨酸作为不含 PEG 的热凝胶

聚合物水溶液的热凝胶行为来自聚合物的亲水部分和疏水部分之间的微妙平衡。通常，聚（乙二醇）（PEG）已被用作迄今为止报道的大多数热凝胶中的亲水性嵌段。然而，最近的论文提出了 PEG 缀合化合物的潜在免疫原性。在这里，我们报告了具有特定分子量的dl-聚丙氨酸 (DL-PA) 的水溶液可以表现出热凝胶行为。特别是，分子量 ( Mn )_为6690 Da 的 DL-PA，DL-PA67，在 30-40 °C 的重要生理温度范围内表现出溶胶到凝胶的转变。¹H NMR和FTIR数据表明，热凝胶化的机制与DL-PA67的脱水和构象从无规卷曲到β-折叠结构的变化有关。向大鼠皮下注射 DL-PA67 水溶液证实了凝胶的形成及其与轻度组织刺激的组织相容性。