Gelation of Na-alginate aqueous solution: A study of sodium ion dynamics via NMR relaxometry
Gelation of Na-alginate aqueous solution: A study of sodium ion dynamics via NMR relaxometry
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海藻酸钠水溶液的凝胶化：通过 NMR 弛豫测定法研究钠离子动力学
DOI：
10.1016/j.carbpol.2017.03.099
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发表时间：
2017-08-01
影响因子：
11.2
通讯作者：
Liu, Ruigang
中科院分区：
文献类型：
--
作者：
Zhao, Congxian;Zhang, Chao;Liu, Ruigang
海藻酸钠（SA）水凝胶具有广泛的应用，包括组织工程、药物递送和预防胃反流的制剂。 SA 溶液凝胶过程中钠离子的动力学对于阐明凝胶过程至关重要。在这项工作中，使用核磁共振 (NMR) 弛豫测量和脉冲场梯度 (PFG) NMR 扩散测量来研究 SA 海藻酸盐凝胶化过程中钠离子的动力学。我们发现，添加二价钙离子后，钠离子处于两种不同的状态，对应于水凝胶中Ca2+交联和未交联的区域。未交联区域内的钠离子是那些从没有 Ca2+ 交联的藻酸盐链中释放出来的钠离子。随着体系中钙离子含量的增加，Ca2+交联区内钠离子的相对含量降低。随着钙离子浓度的增加，Ca2+交联区和非交联区钠离子的弛豫时间T-2逐渐变短和变长，这表明SA链的包裹更加紧密，游离钠离子的扩散空间更大。这项工作阐明了海藻酸钙凝胶中平衡状态下 Na-23(+) 的动力学。 (C) 2017 Elsevier Ltd. 保留所有权利。
Sodium alginate (SA) hydrogels have a wide range of applications including tissue engineering, drug delivery and formulations for preventing gastric reflux. The dynamics of sodium ions during the gelation process of SA solution is critical for clarification of the gelation procedure. In this work, nuclear magnetic resonance (NMR) relaxometry and pulsed-field-gradient (PFG) NMR diffusometry were used to investigate the dynamics of the sodium ions during the gelation of SA alginate. We find that sodium ions are in two different states with the addition of divalent calcium ions, corresponding to Ca2+ crosslinked and un-crosslinked regions in the hydrogels. The sodium ions within the un-crosslinked regions are those released from the alginate chains without Ca2+ crosslinking. The relative content of sodium ions within the Ca2+ crosslinked regions decreased with the increase in the content of calcium ions in the system. The relaxation time T-2 of sodium ions within the Ca2+ crosslinked and un-crosslinked regions shift to shorter and longer relaxation time with the increase in concentration of calcium ion, which indicates the closer package of SA chains and the larger space for the diffusion of free sodium ions. This work clarifies the dynamics of Na-23(+) in a calcium alginate gel at the equilibrium state. (C) 2017 Elsevier Ltd. All rights reserved.