Reorienatational dynamics of cholesterol molecules in thin film surrounded carbon nanotube: Molecular dynamics simulations

Molecular Dynamics Simulations of Water-Mediated Cholesterol Capture within an Open-Ended Single-Walled Carbon Nanotube

The excess concentration of cholesterol in the bloodstream can be brought down to a safer level by utilizing a potential cholesterol-binding agent such as a carbon nanotube (CNT). Here, we have probed solvent-mediated interactions between cholesterol and CNT by performing molecular dynamics simulations and potential-of-mean force (PMF) calculations. Simulations predict favorable interactions between water-mediated cholesterol and CNT owing to strong mutual interactions between them, whereas water plays an opposing role in the association. The breakdown of PMF into its enthalpic and entropic contributions indicates that contrary to traditional entropy-driven hydrophobic association, the cholesterol encapsulation within a CNT is primarily driven by enthalpy.

On the impact of nanotube diameter on biomembrane indentation - Computer simulations study

The influence of the single-walled carbon nanotubes on the phospholipid bilayer has been studied using steered molecular dynamics (SMD) simulations. The impact of different nanotubes on the phospholipid bilayer structure is discussed as well as the speed of indentation. Additionally, a series of simulations with pulling out of the nanotubes from the membrane were performed. The deflection of the membrane in both nanoindenation and extraction processes is also discussed. The self-sealing ability of membrane during this process is examined. Complete degradation of the bilayer was not observed even for the most invasive nanoindentation process studied. The obtained results show that carbon nanotubes can be regarded as potential drug carriers for targeted therapy.

Supramolecular complexes of multivalent cholesterol-containing polymers to solubilize carbon nanotubes in apolar organic solvents

Copolymers of 2-ethylhexyl acrylate (EHA) and cholesteryloxycarbonyl-2-hydroxymethacrylate (CEM) were prepared by reversible addition-fragmentation chain-transfer (RAFT) polymerization. Supramolecular complexes of these copolymers with carbon nanotubes (CNTs) were soluble in THF, toluene, and isooctane. The colloidal solutions remained stable for months without aggregation. The rationale for the choice of CEM was based on the high adsorption energy of cholesterol on the CNT surface, as computed by DFT calculations. Adsorption isotherms were experimentally measured for copolymers of various architectures (statistical, diblock, and star copolymers), thereby demonstrating that 2-5 cholesterol groups were adsorbed per polymer chain. Once the supramolecular complex had dried, the CNTs could be easily resolubilized in isooctane without the need for high-power sonication and in the absence of added polymer. Analysis by atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) indicated that the CNTs were devoid of bundles. The supramolecular complexes could also be employed in an inverse emulsion polymerization of 2-hydroxyethylmethacrylate (HEMA) in isooctane and dodecane, thereby leading to the formation of a continuous polymeric sheath around the CNTs. Thus, this technique leads to the formation of very stable dispersions in non-polar organic solvents, without altering the fundamental properties of the CNTs.