Sao Carlos Institute of Physics, University of Sao Paulo, Sao Carlos, SP, Brazil.
Sao Carlos Institute of Chemistry, University of Sao Paulo, Sao Carlos, SP, Brazil.
Colloids Surf B Biointerfaces. 2022 Jan;209(Pt 2):112146. doi: 10.1016/j.colsurfb.2021.112146. Epub 2021 Oct 2.
Langmuir monolayers are used to simulate the biological membrane environment, acting as a mimetic system of the outer or the inner membrane leaflet. Herein, we analyze the interaction of membrane models with a partially N-acetylated chitosan (Ch35%) possessing a quasi-ideal random pattern of acetylation, full water solubility up to pH ≈ 8.5 and unusually high weight average molecular weight. Lipid monolayers containing dipalmitoyl phosphatidyl choline (DPPC), dipalmitoyl phosphatidyl ethalonamine (DPPE), dipalmitoyl phosphatidyl glycerol (DPPG) or E. coli total lipid extract were spread onto subphases buffered at pH 4.5 or 7.4. The incorporation of Ch35% chitosan caused monolayer expansion and a general trend of decreasing monolayer rigidity with Ch35% concentration. Due to its relatively high content of N-acetylglucosamine (GlcNAc) units, Ch35% interactions with negatively charged monolayers and with E. coli extract were weaker than those involving zwitterionic monolayers or lipid rafts. While the smaller interaction with negatively charged lipids was unexpected, this finding can be attributed to the degree of acetylation (35%) which imparts a small number of charged groups for Ch35% to interact. Chitosan properties are therefore determinant for interactions with model cell membranes, which explains the variability in chitosan bactericide activity in the literature. This is the first study on the effects from chitosans on realistic models of bacterial membranes under physiological pH.
朗缪尔单分子层被用来模拟生物膜环境，作为外膜或内膜小叶的模拟系统。在此，我们分析了具有近乎理想的随机乙酰化模式、完全水溶性直至 pH≈8.5 和异常高的重均分子量的部分 N-乙酰化壳聚糖 (Ch35%) 与膜模型的相互作用。含有二棕榈酰磷脂酰胆碱 (DPPC)、二棕榈酰磷脂酰乙醇胺 (DPPE)、二棕榈酰磷脂酰甘油 (DPPG) 或大肠杆菌总脂质提取物的脂质单层被铺展在 pH 4.5 或 7.4 的亚相中。Ch35%壳聚糖的加入导致单分子层膨胀，并且单分子层刚性随 Ch35%浓度的增加而降低。由于其相对较高的 N-乙酰葡萄糖胺 (GlcNAc) 单元含量，Ch35%与带负电荷的单层和大肠杆菌提取物的相互作用比与两性离子单层或脂质筏的相互作用弱。虽然与带负电荷的脂质的较小相互作用出乎意料，但这一发现可归因于乙酰化程度（35%），其赋予 Ch35% 较少的带电基团进行相互作用。因此，壳聚糖的性质是决定其与模型细胞膜相互作用的决定因素，这解释了文献中壳聚糖杀菌剂活性的可变性。这是首次在生理 pH 下研究壳聚糖对细菌膜真实模型的影响。
