School of Chemical Engineering, Sichuan University, 24 South Section 1, Yihuan Road, Chengdu, Sichuan Province 610065, P. R. China.
J Biomater Sci Polym Ed. 2011;22(15):2041-61. doi: 10.1163/092050610X530982. Epub 2010 Oct 27.
Amphiphilic methacrylate co-polymers recently demonstrated antimicrobial activity. To understand their activity mechanism, we prepared three homologous methacrylate co-polymers with activity ranging from inactive (MMA) over specifically active (EMA) to non-specifically active (BMA) against bacteria and human erythrocytes. Fluorescent dye leakage assays were used to characterize their membrane-disrupting activity against liposomes of different compositions. From bacterial membrane-mimicking liposomes (composed of Escherichia coli extract or 20:80 DOPG/DOPE), the two active forms, EMA and BMA, caused more dye leakage than the inactive MMA, which mirrors their antibacterial activity trend. From mammalian membrane-mimicking liposomes (composed of DOPC or 20:80 DOPG/DOPC), the highly hemolytic BMA caused significantly more leakage than MMA and EMA, which mirrors its hemolytic activity trend. Moreover, to dissect the effect of intrinsic membrane curvature from that of membrane charge, we used a ternary membrane with constant charge and tunable intrinsic curvature. Specifically, we used membranes composed of DOPG/DOPE/DOPC with constant DOPG content and varying DOPE/DOPC ratio. To significantly disrupt this model, methacrylate co-polymers with different activity profiles required a different minimum threshold DOPE content. In contrast, variation in DOPG/DOPC ratio at constant DOPE concentration did not show a similar influence on the selective membrane-disrupting activity of these co-polymers. Our results suggested that the intrinsic membrane curvature, rather than membrane charge, may play a major role in the selective membrane-disrupting activity of methacrylate co-polymers. Since more PE lipids exist in bacterial membranes than in eukaryotic membranes, our results imply that negative-intrinsic-curvature lipids such as PE may contribute to the selective antimicrobial activity.
两亲性甲基丙烯酸酯共聚物最近表现出抗菌活性。为了了解其作用机制，我们制备了三种具有活性的同系甲基丙烯酸酯共聚物，其活性从无活性（MMA）到特异性活性（EMA）再到非特异性活性（BMA），针对细菌和人红细胞。荧光染料渗漏实验用于表征它们对不同组成的脂质体的膜破坏活性。从细菌膜模拟脂质体（由大肠杆菌提取物或 20:80 DOPG/DOPE 组成）中，两种活性形式的 EMA 和 BMA 引起的染料渗漏量多于无活性的 MMA，这反映了它们的抗菌活性趋势。从哺乳动物膜模拟脂质体（由 DOPC 或 20:80 DOPG/DOPC 组成）中，高度溶血的 BMA 引起的渗漏量明显多于 MMA 和 EMA，这反映了其溶血活性趋势。此外，为了从膜电荷中分离出固有膜曲率的影响，我们使用了具有恒定电荷和可调节固有曲率的三元膜。具体来说，我们使用 DOPG/DOPE/DOPC 组成的膜，DOPG 含量恒定，DOPE/DOPC 比例可变。为了显著破坏这种模型，具有不同活性谱的甲基丙烯酸酯共聚物需要不同的最小 DOPE 含量阈值。相比之下，在恒定 DOPE 浓度下改变 DOPE/DOPC 比例不会对这些共聚物的选择性膜破坏活性产生类似影响。我们的结果表明，固有膜曲率而不是膜电荷可能在甲基丙烯酸酯共聚物的选择性膜破坏活性中起主要作用。由于细菌膜中存在的 PE 脂质多于真核膜，因此我们的结果表明，负曲率脂质如 PE 可能有助于选择性抗菌活性。
