Betulinic acid and 3-o-acetyl-betulinic acid interactions with external and internal surface of boron-nitride nanotubes: A DFT and MD investigation

Abstract

In present study, density-functional theory and molecular simulations were carried out to examine adsorption of anticancer drug betulinic acid and its analogue 3-o-acetyl-betulinic acid on external and internal surfaces of boron nitride nanotubes. To investigate effects of nanotube diameter and chirality on drugs adsorption, nanotubes including (8,8), (9,9), (10,10) and (16,0) were considered. Then, interactions of drugs with external and internal surfaces of these nanotubes were assessed. The results showed that both drugs are better adsorbed on internal nanotubes than on their external surface. Comparing energy amounts showed that adsorption energies are affected by nanotube diameter and both drugs molecules are adsorbed better on the internal nanotube (9,9) than (8,8) and (10,10). It was found that 3-o-acetyl-betulinic acid has stronger interaction with the boron nitride nanotubes internal surface. Results also showed that adsorption of drug molecules on nanotubes increases nanotubes polarity, which in turn improves solubility of nanotubes in water.