Abstract Dissolved natural or modified chitosans are used as the carriers of bioactive compounds which demands knowledge on how these macromolecules bind chemicals in solutions. This work examines binding of ionizable salicylic acid (SA), a medicine chemical and plant hormone, to chitosan and its derivative obtained by amine N alkylation with n-C6H13. Binding was studied at two pHs, below the chitosan's pKa, by performing dialysis with a 3500 Da cut-of membrane, followed by a spectrophotometric determination of SA concentrations in the membrane-separated compartments. SA-chitosan binding obeys reversible linear isotherms showing distinct preferences for SA to distribute from water to macromolecules with a coefficient reaching up to few hundreds (L kg−1), depending on pH and NaCl concentration. Both SA molecules and anions bind to dissolved chitosan. Although the SA anion-chitosan interactions tend to dominate, they can be suppressed by competing anions. Chitosan N-alkylation is associated with a modest decreasing effect on SA binding. For water-soluble formulations of bioactive substances, binding quantification may help to differentiate between the effects of concentration of chitosan-bound active chemicals and the ability of complexes to pass biological barriers.

中文翻译：

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溶液中水杨酸与壳聚糖及其 N-烷基化衍生物的结合相互作用：平衡透析研究

摘要 溶解的天然或改性壳聚糖被用作生物活性化合物的载体，这需要了解这些大分子如何结合溶液中的化学物质。这项工作检查了可电离水杨酸 (SA)（一种药物化学物质和植物激素）与通过胺 N 烷基化与 n-C6H13 获得的壳聚糖及其衍生物的结合。在低于壳聚糖 pKa 的两个 pH 值下研究结合，通过用 3500 Da 截断膜进行透析，然后分光光度法测定膜分离隔室中的 SA 浓度。SA-壳聚糖结合遵循可逆线性等温线，显示出 SA 从水分布到大分子的明显偏好，其系数高达数百 (L kg-1)，具体取决于 pH 值和 NaCl 浓度。SA 分子和阴离子都与溶解的壳聚糖结合。尽管 SA 阴离子-壳聚糖相互作用往往占主导地位，但它们可以被竞争阴离子抑制。壳聚糖 N-烷基化与对 SA 结合的适度降低影响有关。对于生物活性物质的水溶性制剂，结合定量可能有助于区分壳聚糖结合活性化学品浓度的影响和复合物通过生物屏障的能力。