Molecular dynamics properties of varying amounts of the anticancer drug gemcitabine inside an open-ended single-walled carbon nanotube

To investigate the loading of multiple drugs inside single-walled carbon nanotubes (SWCNTs), molecular dynamics simulations were applied to the gemcitabine–SWCNT system with from one to six drug molecules being confined inside the SWCNT cavity. At low drug concentrations (1–4 gemcitabines inside each SWCNT), the π–π stacking of two cytosine rings of adjacent gemcitabine molecules caused them to orientate towards each other and move together inside the SWCNT. In contrast, at high drug concentrations (encapsulated gemcitabines ⩾5), the close contact of gemcitabines promoted electrostatic interactions through hydrogen bonding rather than the π–π stacking interaction from their cytosine rings.