摘要：目的 针对“平行放置于细胞膜表面的两单壁碳纳米管”系统，探究两碳管间相互作用对膜包裹碳管方式的影响，并给出能量最优的构象。 方法 建立考虑两根碳管间范德华相互作用的膜包裹碳管的力学模型，并引入反映细胞膜形态的参数以及描述碳管相对位置的参数。利用基于Helfrich自由能的连续介质力学建模，计算膜弯曲能量，并利用Lennard-Jones势描述碳管之间的相互作用。通过查表法计算系统不同位置的自由能，并给出细胞膜包裹碳管的典型结构。结果 与未考虑管间相互作用的情况相比，系统自由能曲线出现了较大改变：在碳管间距约为0.3倍管半径时，能量曲线上出现深势阱；随着碳管间距增大，自由能恢复到没有管间相互作用能时的大小。结论 引入碳管间相互作用能后，膜包裹碳管的方式发生变化，两碳管倾向于以“触碰到一起”的方式进行协同胞吞。论文结果有望为理解并设计基于纳米管的药物输运系统，提供理论借鉴。
Abstract: Objective For the system of two single-walled carbon nanotubes (CNTs) placed in parallel onto a cell membrane, we investigate the effect of the interaction between carbon nanotubes on the wrapping manner of carbon tubes by the membrane, and obtain the energy-optimized configurations. Methods We develop a physical model for membrane-wrapped CNTs considering the interaction between two CNTs, and introduce parameters describing the morphology of the cell membrane and positions of CNTs. The Helfrich model based on continuum mechanics is used to calculate the membrane’s bending energy and the Lennard-Jones potential is introduced to describe the interaction between CNTs. We obtain the free energy of the system at different distances of NTs by the look-up table method, and the typical configurations of the system. Results Compared to the case wherein the interaction between CNTs is not considered, the free energy profile of the system significantly changed: the deep well appears on the energy curve at a distance between CNTs of carbon ~0.3 times the tube diameter; as the distance between CNTs increases, the energy returns to the case wherein the interaction between CNTs is not considered. Conclusions Under the consideration of the interaction between CNTs, we find that the wrapping manner of CNTs by the cell membrane is changed, and the two CNTs tend to contact during their endocytosis. This work may be helpful in understanding and developing novel nanotube-based system for drug delivery.