Carbon nanotubes (CNTs) have been regarded as one of the most hopeful candidates for transporting drugs to target cells because of their huge surface area, hollow structure, and enhanced cellular uptake. The idea of using their hollow channels as containers to load and unload small drug molecules has been proposed for many years. However, the encapsulation of drugs into CNTs, the internalization of CNT-drug conjugates in the cell membrane, and the successive drug release at the atomic level remain unclear. In this work, we performed molecular dynamics simulations to investigate the potential application of CNTs as a nanocarrier to transport and deliver drug molecules. Pregabalin (PRE) was selected as a model drug, as its size and polarity are suitable for transporting through CNT hollow channels. The simulation can be divided into three stages. First, PRE was encapsulated into the optimized CNT in the water solution and the PRE–CNT complex was formed, then this complex readily entered the lipid bilayer and finally PRE released one by one from CNTs into the membrane. Compared with the direct insertion of PRE in the membrane, the PRE–CNT complex can reduce the energy barrier to enter the membrane and pass the bilayer center. The fast release of PRE from CNTs benefits from its amphipathicity. The electrostatic interaction between its polar groups and lipid headgroups pull the PRE molecules out of the CNT. The results indicate that both the loading and unloading of PRE based on CNTs are energetically favorable. CNTs exhibit great potential as nanovehicles to carry and deliver particular drug molecules.

An unexpected hydrophobicity with a contact angle of 82° on (OH)2-SAM terminated only with two hydrophilic OH groups was found, which is attributed to the formation of a hexagonal-ice-like H-bonding structure in the OH matrix of (OH)2-SAM.

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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.

The OH-terminated self-assembled monolayers, as protein-resistant surfaces, have significant potential in biocompatible implant devices, which can avoid or reduce adverse reactions caused by protein adhesion to biomaterial surfaces, such as...