Predicting the efficiency of polyethylene glycol-functionalised graphene in delivery of temozolomide anticancer drug and investigating the effect of pH on the drug release process: DFT and free energy calculations

Abstract

The adsorption mechanism of temozolomide (TMZ) anticancer drug on functionalised graphene nanosheet with polyethylene glycol (PEG-GNS) is investigated using density functional theory (DFT) calculations and molecular dynamics (MD) simulations. The probability of the formation of f – f stacking, hydrogen bond, and the simultaneous effect of these two interactions are investigated. The obtained results from the DFT calculations showed that interaction of TMZ with PEG-GNS is exothermic, and f – f stacking interaction between the aromatic rings of TMZ and GNS surface has a vital role in the adsorption process. Also, it is found that the most stable complex is formed in a system where the drug can interact with the graphene surface and PEG agent via f – f stacking and hydrogen bond interactions. Furthermore, MD simulations are performed to understand the effects of pH variation on the adsorption process. The obtained results illustrated that the interaction of the drug with the proposed carrier in the neutral system is stronger than protonated systems. The binding free energy value is reduced by decreasing the pH level. It is observed that interactions between TMZ and the nanocarrier are strong inbiological pH conditions. While these interactions become weaker in the acid condition.