Molecular structure and electronic properties of adsorbed Ampyra drug on the functionalized graphene nanosheet: A DFT study

In this study, the adsorption of Ampyra (Am) molecule (C5H6N2) on the graphene nanosheets functionalized with hydroxyl (G-OH), epoxide (G-O), carbonyl (G-CO), and carboxyl (G-COOH) groups have been investigated by density functional theory. All calculations have been done using M06-2X [1] functional along with the 6-31G(d,p) basis set in the gas phase.Table 1 shows that, by functionalization of graphene nanosheet with a carboxyl group, the maximum adsorption energy (Eads) between Ampyra drug and the nanosheet is obtained. Diminish in energy gap (Eg) and global hardness (ƞ) with the adsorption of Ampyra on the functionalized nanosheets shows that the reactivity of functionalized complexes increases upon loading of the drug molecule.When Ampyra molecule approaches on the functionalized nanosheets, electrons are transferred from higher chemical potential to the lower electronic chemical potential, until the electronic chemical potentials become identical.Considering the amount of chemical potential values of Table confirm that electrons will flow from a definite occupied orbital in the TG drug to definite empty orbital in G-COOH, G-O, G-CO and G-OH nanosheets.These results are in accordance with the obtained electrophilicity index values of the studied segments at the considered functionalized complexes.These results reveal that the chemical modification of graphene nanosheet using covalent functionalization scheme is an effectual approach for loading and delivery of Ampyra drug molecule within biological systems.