Department of Chemical Engineering, University of Rhode Island , 51 Lower College Road, Kinston, Rhode Island 02881, United States.
Langmuir. 2018 Feb 6;34(5):2039-2045. doi: 10.1021/acs.langmuir.7b03743. Epub 2018 Jan 23.
We have investigated the surface activity of poly(ethylene glycol) (PEG)-coated silver nanoparticles (Ag-PEG) in the presence or absence of lipid monolayers comprised of monounsaturated dioleoylphosphocholine and dioleoylphosphoglycerol (DOPC/DOPG; 1:1 mol ratio). Dynamic measurements of surface pressure demonstrated that Ag-PEG were surface-active at the air/water interface. Surface excess concentrations suggested that at high Ag-PEG subphase concentrations, Ag-PEG assembled as densely packed monolayers in the presence and absence of a lipid monolayer. The presence of a lipid monolayer led to only a slight decrease in the excess surface concentration of Ag-PEG. Surface pressure-area isotherms showed that in the absence of lipids Ag-PEG increased the surface pressure up to 45 mN m upon compression before the Ag-PEG surface layer collapsed. Our results suggest that surface activity of Ag-PEG was due to hydrophobic interactions imparted by a combination of the amphiphilic polymer coating and the hydrophobic dodecanethiol ligands bound to the Ag-PEG surface. With lipid present, Ag-PEG + lipid surface pressure-area (π-A) isotherms reflected Ag-PEG incorporation within the lipid monolayers. At high Ag-PEG concentrations, the π-A isotherms of the Ag-PEG + lipid films closely resembled that of Ag-PEG alone with a minimal contribution from the lipids present. Analysis of the subphase silver (Ag) and phosphorus (P) concentrations revealed that most of the adsorbed material remained at the air/lipid/water interface and was not forced into the aqueous subphase upon compression, confirming the presence of a composite Ag-PEG + lipid film. While interactions between "water-soluble" nanoparticles and lipids are often considered to be dominated by electrostatic interactions, these results provide further evidence that the amphiphilic character of a nanoparticle coating can also play a significant role.
我们研究了聚乙二醇（PEG）包覆的银纳米粒子（Ag-PEG）在存在或不存在由单不饱和二油酰基磷酸胆碱和二油酰基磷酸甘油（DOPC/DOPG；1:1 摩尔比）组成的脂质单层的情况下的表面活性。表面压力的动态测量表明，Ag-PEG 在空气/水界面具有表面活性。表面过剩浓度表明，在高 Ag-PEG 亚相浓度下，Ag-PEG 在存在和不存在脂质单层的情况下组装成密集堆积的单层。脂质单层的存在仅导致 Ag-PEG 的过剩表面浓度略有降低。表面压力-面积等温线表明，在不存在脂质的情况下，Ag-PEG 在压缩前将表面压力增加至 45 mN m 以上，然后 Ag-PEG 表面层坍塌。我们的结果表明，Ag-PEG 的表面活性是由于两亲聚合物涂层和结合在 Ag-PEG 表面的疏水性十二硫醇配体赋予的疏水相互作用所致。有脂质存在时，Ag-PEG+脂质表面压力-面积（π-A）等温线反映了 Ag-PEG 掺入脂质单层中。在高 Ag-PEG 浓度下，Ag-PEG+脂质膜的 π-A 等温线与单独的 Ag-PEG 非常相似，而存在的脂质的贡献最小。亚相中银（Ag）和磷（P）浓度的分析表明，大部分吸附材料仍留在空气/脂质/水界面，在压缩时不会被迫进入水亚相，这证实了存在复合 Ag-PEG+脂质膜。虽然“水溶性”纳米粒子和脂质之间的相互作用通常被认为主要由静电相互作用主导，但这些结果进一步证明了纳米粒子涂层的两亲特性也可以发挥重要作用。
