Interaction of nanoparticles with lipid films: the role of symmetry and shape anisotropy

The bioactivity, biological fate and cytotoxicity of nanomaterials when they come into contact with living organisms are determined by their interaction with biomacromolecules and biological barriers. In this context, the role of symmetry/shape anisotropy of both the nanomaterials and biological interfaces in their mutual interaction, is a relatively unaddressed issue. Here, we study the interaction of gold nanoparticles (NPs) of different shapes (nanospheres and nanorods) with biomimetic membranes of different morphology, i.e. flat membranes (2D symmetry, representative of the most common plasma membrane geometry), and cubic membranes (3D symmetry, representative of non-lamellar membranes, found in Nature under certain biological conditions). For this purpose we used an ensemble of complementary structural techniques, including Neutron Reflectometry, Grazing Incidence Small-Angle Neutron Scattering, on a nanometer lengthscale and Confocal Laser Scanning Microscopy on a micrometer length scale. We found that the structural stability of the membrane towards NPs is dependent on the topological characteristic of the lipid assembly and of the NPs, where a higher symmetry gave higher stability. In addition, Confocal Laser Scanning Microscopy analyses highlighted that NPs interact with cubic and lamellar phases according to two distinct mechanisms, related to the different structures of the lipid assemblies. This study for the first time systematically addresses the role of NPs shape in the interaction with lipid assemblies with different symmetry. The results will contribute to improve the fundamental knowledge on lipid interfaces and will provide new insights on the biological function of phase transitions as a response strategy to the exposure of NPs.

纳米材料与生物体接触时的生物活性、生物学归趋及细胞毒性，由其与生物大分子（biomacromolecules）和生物屏障（biological barriers）的相互作用所决定。在此研究背景下，纳米材料与生物界面二者的对称性/形状各向异性（symmetry/shape anisotropy）在二者互作中的作用，仍是一个相对未被充分探究的科学问题。本研究针对不同形貌的金纳米颗粒（gold nanoparticles, NPs，包括纳米球（nanospheres）与纳米棒（nanorods））与不同形态仿生膜（biomimetic membranes）的相互作用展开探究：所涉仿生膜包括代表最常见质膜几何结构（plasma membrane geometry）的平面膜（flat membranes，二维对称性（2D symmetry）），以及自然界特定生物条件下存在的非层状膜（non-lamellar membranes）所对应的立方膜（cubic membranes，三维对称性（3D symmetry））。为此，我们采用了一套互补的结构表征技术体系：在纳米尺度下使用中子反射法（Neutron Reflectometry）与掠入射小角中子散射（Grazing Incidence Small-Angle Neutron Scattering），在微米尺度下使用共聚焦激光扫描显微镜（Confocal Laser Scanning Microscopy）。研究结果表明，膜对纳米颗粒的结构稳定性取决于脂质组装体（lipid assembly）与纳米颗粒的拓扑特性，对称性越高则膜的稳定性越强。此外，共聚焦激光扫描显微镜分析结果显示，纳米颗粒与立方相和层状相（lamellar phases）的相互作用遵循两种截然不同的机制，这与脂质组装体的结构差异密切相关。本研究首次系统性地探讨了纳米颗粒形貌与不同对称性脂质组装体相互作用的关联。本研究成果不仅有助于深化我们对脂质界面的基础认知，还可为理解作为纳米颗粒暴露响应策略的相变（phase transitions）生物学功能提供全新视角。