Carbon Nanotubes Translocation through a Lipid Membrane and Transporting Small Hydrophobic and Hydrophilic Molecules

Yiyi Gao,Liang Chen,Guoquan Zhou,Songwei Zeng,Jun Wu,Zhikun Wang,Xiaogang Wang,Junlang Chen,Dangxin Mao

doi:10.3390/app9204271

Abstract

Carbon nanotubes (CNTs) are extensively adopted in the applications of biotechnology and biomedicine. Their interactions with cell membranes are of great importance for understanding the toxicity of CNTs and the application of drug delivery. In this paper, we use atomic molecular dynamics simulations to study the permeation and orientation of pristine and functionalized CNTs in a lipid bilayer. Pristine CNT (PCNT) can readily permeate into the membrane and reside in the hydrophobic region without specific orientation. The insertion of PCNTs into the lipid bilayer is robust and independent on the lengths of PCNTs. Due to the presence of hydroxyl groups on both ends of the functionalized CNT (FCNT), FCNT prefers to stand upright in the lipid bilayer center. Compared with PCNT, FCNT is more suitable to be a bridge connecting the inner and outer lipid membrane. The inserted CNTs have no distinct effects on membrane structure. However, they may block the ion channels. In addition, preliminary explorations on the transport properties of CNTs show that the small hydrophobic molecule carbon dioxide can enter both PCNT and FCNT hollow channels. However, hydrophilic molecule urea is prone to penetrate the PCNT but finds it difficult to enter the FCNT. These results may provide new insights into the internalization of CNT in the lipid membrane and the transport properties of CNTs when embedded therein.

Highlights

The introduction of carbon nanoparticles into the biotechnological and biomedical fields has opened a large number of applications, such as biosensors and drug carriers [1,2,3,4,5,6,7,8]
The orientation of Pristine carbon nanotube (CNT) (PCNT) out and in the membrane is monitored by the tilt angle (α), which is defined as the included angle between the central axis of PCNT and the membrane plane
Using molecular dynamics (MD) simulations, we studied the translocation of PCNT from the aqueous environment to the lipid bilayer interior and compared the behavior of PCNT in the membrane with that of functionalized CNT (FCNT)

Summary

Introduction

The introduction of carbon nanoparticles into the biotechnological and biomedical fields has opened a large number of applications, such as biosensors and drug carriers [1,2,3,4,5,6,7,8]. One such kind of nanomaterial is the carbon nanotube (CNT), which can deliver peptides [6,8], proteins [4], and nucleic acids [5] to different cells. Two very recent works show that short CNTs can transport water, protons, and small ions after the spontaneous insertion into the live cell membranes [18]

Methods

Results

Conclusion