A. N. Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, Russia, Vavilov street 28, Moscow, 119991 Russia.
Kazan Federal University , Kremlyovskaya street 18, Kazan, 420008 Russia.
Biomacromolecules. 2017 May 8;18(5):1491-1498. doi: 10.1021/acs.biomac.7b00039. Epub 2017 Apr 12.
Oligochitosan (short chain chitosan) is more soluble in acidic aqueous media than a high molecular weight (MW) chitosan, but its antimicrobial activity decreases with increase in degree of acetylation (DA) and increase in pH above a critical pH threshold point. In the present study, oligochitosans varying in MW were additionally N-acetylated and their self-assembly properties and antibacterial activity toward Staphylococcus aureus and Escherichia coli were investigated in a wide pH range as a function of MW and DA. Light scattering studies reveals that reacetyleted oligochitosan with M ≤ 11 kDa is completely soluble in alkaline media (up to pH 12.5), if its DA is not less than 16%. Reacetylated chitosans with DA ∼ 30% are solubile in the entire pH range up to 12.5, if their M is not higher than 25 kDa, but they aggregate and precipitate from the solution at pH ≥ 8 when their M is above 25 kDa. Considering the influence of DA and MW, the antibacterial activity of reacetylated oligochitosans is maximal in the short interval of DA 16-28% at pH 7.4. These results are promising for expanding practical application of oligochitosan in pharmaceutical, cosmetic, and food compositions.
低聚壳聚糖（短链壳聚糖）在酸性水介质中的溶解度高于高分子量壳聚糖，但随着乙酰化程度（DA）的增加和 pH 值超过临界 pH 值阈值的增加，其抗菌活性降低。在本研究中，MW 不同的低聚壳聚糖进一步进行 N-乙酰化，研究了其在宽 pH 范围内的自组装特性和对金黄色葡萄球菌和大肠杆菌的抗菌活性，作为 MW 和 DA 的函数。光散射研究表明，如果 DA 不低于 16%，MW 不超过 11 kDa 的乙酰化低聚壳聚糖完全可溶于碱性介质（高达 pH 12.5）。DA 约为 30%的再乙酰化壳聚糖在整个 pH 范围内（高达 12.5）都是可溶的，如果它们的 MW 不高于 25 kDa，但当 MW 高于 25 kDa 时，它们在 pH≥8 时会聚集和沉淀出溶液。考虑到 DA 和 MW 的影响，再乙酰化低聚壳聚糖在 pH 7.4 的 DA 16-28%的短间隔内具有最大的抗菌活性。这些结果为扩大低聚壳聚糖在药物、化妆品和食品制剂中的实际应用提供了希望。
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