Department of Biomedical Engineering, Amirkabir University of Technology, P.O. Box 1587, 4413, Tehran, Iran.
J Mater Sci Mater Med. 2011 Oct;22(10):2365-75. doi: 10.1007/s10856-011-4396-2. Epub 2011 Jul 21.
Alginate is a family of natural polysaccharides, widely used in industry and medicine for many applications, with its non toxic nature, gentle sol/gel transition procedure and low cost, alginate inferior biomechanical properties have limited its utility especially in tissue engineering. Additionally, ionically cross-linked alginate hydrogels generally lose most of their initial mechanical and swelling properties within a few hours in physiological solution. In order to overcome these limitations, the referenced alginate was treated by covalent fixation of octadecyl chains onto the polysaccharide backbone by esterification. In semi dilute solution, intermolecular hydrophobic interactions of long alkyl chains result in the formation of physical hydrogels, which can then be reinforced by the addition of calcium chloride. FTIR studies clearly showed the presence of ester bonds at 1612 and 1730 cm(-1) indicating that the alkyl groups are incorporated in the backbone of resulting polymer. The endothermic peak and exothermic peak present in the DSC thermogram of Alg-C18 had shifted to lower temperatures comparing to native alginate (from 106 to 83°C and from 250 to 245°C, respectively) due to the esterification reaction that leads to high hydrophobic nature of the modified sample. From rheological experiments, it can be inferred that the combination of both calcium bridges and intermolecular hydrophobic interaction in the treated alginate leads to enhanced gel strength accompanied by more stable structure in physiological solution comparing to native sodium alginate hydrogel. Finally, the modified alginate tended to have no toxic effects on mesenchymal stem cell culture, rather it supported MSC chondrogenic differentiation.
藻酸盐是一类天然多糖，因其无毒、温和的溶胶/凝胶转变过程和低成本，在工业和医学领域得到了广泛的应用。然而，藻酸盐较差的生物力学性能限制了其在组织工程中的应用。此外，离子交联的藻酸盐水凝胶在生理溶液中通常在几小时内就会失去大部分初始机械性能和溶胀性能。为了克服这些限制，参考的藻酸盐通过用十八烷基链通过酯化反应共价固定在多糖主链上来进行处理。在半稀溶液中，长烷基链的分子间疏水相互作用导致形成物理水凝胶，然后可以通过添加氯化钙来增强。FTIR 研究清楚地表明在 1612 和 1730 cm(-1)处存在酯键，表明烷基基团被整合到所得聚合物的主链中。与天然藻酸盐相比，Alg-C18 的 DSC 热图谱中的吸热峰和放热峰分别向低温移动（从 106°C 到 83°C，从 250°C 到 245°C），这是由于酯化反应导致改性样品具有高疏水性。从流变学实验可以推断，处理后的藻酸盐中钙桥和分子间疏水相互作用的结合导致凝胶强度增强，并且在生理溶液中结构更稳定，与天然的藻酸钠水凝胶相比。最后，改性藻酸盐对间充质干细胞培养没有毒性作用，反而支持 MSC 软骨分化。
