Department of Engineering Mechanics, Shanghai Jiao Tong University, Shanghai 200240, China.
Nanoscale. 2012 Jun 21;4(12):3768-75. doi: 10.1039/c2nr30379e. Epub 2012 May 21.
The cell uptake rate of nanoparticles (NPs) coated with mixed hydrophilic/hydrophobic ligands is known to be strongly influenced by the ligand pattern on the nanoparticle surface. To help reveal the physical mechanism behind this intriguing phenomenon, here we perform dissipative particle dynamics simulations to analyze the evolution of free energy as the ligand-coated NPs pierce through a lipid bilayer. Four characteristic ligand patterns are considered: striated NPs with alternating hydrophilic and hydrophobic groups compared to NPs with randomly mixed ligands at the same hydrophilic to hydrophobic ratio, as well as NPs coated with homogeneous hydrophilic or hydrophobic ligands. The free energy analysis indicates that among the four ligand patterns under study, the striated NP encounters the lowest energy barrier during translocation across the membrane. Further analysis reveals that the translocation of the striated NP is facilitated by the constraint of its rotational degree of freedom by the anisotropic ligand pattern, which prevented the free energy of the system from sinking to a deeper valley as the NP passes through the hydrophobic core of the bilayer. Finally, the critical forces required for almost instant penetration of these patterned NPs across the bilayer are calculated and shown to be consistent with the free energy analysis. These findings provide useful guidelines for the molecular design of patterned NPs for controllable cell penetrability.
具有混合亲水/疏水配体的纳米颗粒 (NPs) 的细胞摄取率已知强烈受到纳米颗粒表面配体模式的影响。为了帮助揭示这一有趣现象背后的物理机制,我们在这里进行耗散粒子动力学模拟,以分析配体包覆的 NPs 穿透脂质双层时自由能的演变。考虑了四种特征配体模式:与具有相同亲水-疏水比的随机混合配体的 NPs 相比,具有交替亲水和疏水基团的条纹状 NPs,以及涂有均相亲水或疏水配体的 NPs。自由能分析表明,在所研究的四种配体模式中,条纹状 NP 在跨膜转运过程中遇到的能量屏障最低。进一步的分析表明,条纹状 NP 的转运受到各向异性配体模式对其旋转自由度的限制,这阻止了系统的自由能在 NP 通过双层的疏水性核心时下沉到更深的谷值。最后,计算了这些图案化 NPs 几乎瞬间穿透双层所需的临界力,并表明与自由能分析一致。这些发现为可控细胞穿透性的图案化 NPs 的分子设计提供了有用的指导。