Teshima Ryota, Osawa Shigehito, Kawano Yayoi, Hanawa Takehisa, Kikuchi Akihiko, Otsuka Hidenori
Department of Chemistry, Graduate School of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601, Japan.
Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601, Japan.
ACS Omega. 2023 Feb 16;8(8):7800-7807. doi: 10.1021/acsomega.2c07552. eCollection 2023 Feb 28.
Anionic polysaccharides, including low-methoxy (LM) pectin, are extensively used in biomaterial applications owing to their safety, biocompatibility, and feasibility in constructing supramolecular assemblies by forming egg-box structures with divalent cations. Mixing an LM pectin solution with CaCO spontaneously forms a hydrogel. The gelation behavior can be controlled by adding an acidic compound to change the solubility of CaCO. CO is used as the acidic agent and can be easily removed after gelation, thereby reducing the acidity of the final hydrogel. However, CO addition has been controlled under varied thermodynamical conditions; therefore, specific CO effects on gelation are not necessarily visualized. To evaluate the CO impact on the final hydrogel, which would be extended to control hydrogel properties further, we utilized carbonated water to supply CO into the gelation mixture without changing its thermodynamic conditions. The addition of the carbonated water accelerated gelation and significantly increased the mechanical strength, promoting cross-linking. However, the CO volatilized into the atmosphere, and the final hydrogel became more alkaline than that without the carbonated water, probably because a considerable amount of the carboxy group was consumed for cross-linking. Moreover, when aerogels were prepared from the hydrogels with carbonated water, they exhibited highly ordered networks of elongated porosity in scanning electron microscopy, proposing an intrinsic structural change by CO in the carbonated water. We also controlled the pH and strength of the final hydrogels by changing the CO amounts in the carbonated water added, thereby validating the significant effect of CO on hydrogel properties and the feasibility of using carbonated water.
包括低甲氧基（LM）果胶在内的阴离子多糖，因其安全性、生物相容性以及通过与二价阳离子形成蛋盒结构构建超分子组装体的可行性，而在生物材料应用中被广泛使用。将LM果胶溶液与碳酸钙混合会自发形成水凝胶。通过添加酸性化合物改变碳酸钙的溶解度，可以控制凝胶化行为。二氧化碳用作酸性剂，凝胶化后可轻松去除，从而降低最终水凝胶的酸度。然而，二氧化碳的添加在不同的热力学条件下受到控制；因此，二氧化碳对凝胶化的具体影响不一定能显现出来。为了评估二氧化碳对最终水凝胶的影响，并进一步扩展以控制水凝胶的性质，我们利用碳酸水在不改变其热力学条件的情况下向凝胶化混合物中供应二氧化碳。碳酸水的添加加速了凝胶化并显著提高了机械强度，促进了交联。然而，二氧化碳挥发到大气中，最终的水凝胶比没有添加碳酸水的水凝胶碱性更强，这可能是因为大量羧基用于交联。此外，当用碳酸水从水凝胶制备气凝胶时，在扫描电子显微镜下它们呈现出高度有序的细长孔隙网络，表明碳酸水中的二氧化碳引起了内在的结构变化。我们还通过改变添加的碳酸水中二氧化碳的量来控制最终水凝胶的pH值和强度，从而验证了二氧化碳对水凝胶性质的显著影响以及使用碳酸水的可行性。
