Solvent/co-solvent effects on the electronic properties and adsorption mechanism of anticancer drug Thioguanine on Graphene oxide surface as a nanocarrier: Density functional theory investigation and a molecular dynamics

In this work, the adsorption of Thioguanine (TG) anticancer drug on the surface of Graphene oxide (GO) nanosheet has investigated using density functional theory (DFT) and molecular dynamics simulation (MDs). Quantum mechanics calculations by two methods including M06-2X/6-31G** and omega B97X-D/6-31G** have been employed to calculate the details of energetic, geometric, and electronic properties of the TG molecule interacting with Graphene oxide nanosheet (GONS). DFT calculations confirmed that the strongest adsorption is observed when hydrogen bond interactions between TG molecule and the functional groups of Graphene oxide nanosheet are predominate. In all calculations, solvent effects have been considered in water using the PCM method. It is found that TG molecule can be adsorbed on Graphene oxide with negative solvation energy, indicating the TG adsorption on Graphene oxide surfaces is thermodynamically favored. Moreover, MD simulations are examined to understand the solvent/co-solvent effect (water, ethanol, nicotine) on the Thioguanine drug delivery through Graphene oxide. The results of RDF patterns and the van der Waals energy calculations show that interaction between TG drugs and the Graphene oxide surface is stronger in water solvent compared to the other co-solvent. The obtained MD results illustrate that when nicotine and ethanol exist in the system, the drug takes longer time to bind with GO nanosheet and the system becomes unstable. It can be concluded that Graphene oxide can be a promising candidate in water media for delivery the TG molecule. (C) 2017 Elsevier B.V. All rights reserved.