The effect of type and concentration of functional groups on the molecular adsorption of paclitaxel onto graphene oxide in the aqueous environments using molecular dynamics simulations

Paclitaxol (PTX) is one of the well-known drugs that has been widely used for chemotherapy of a wide spectrum of cancers. Recently, advanced drug delivery systems using nano-carriers with high selectivity have been used for cancer therapy. Graphene nanostructure and its derivatives, i.e., graphene oxide (GO), are promising candidates for biological applications, such as drug delivery, because of their high specific surface areas. Due to hydrophobicity of graphene, it is not easily dispersed in water. Therefore, functional groups are added to it. In this study, we investigated adsorption of paclitaxel (PTX) drug molecule onto graphene oxide (GO) in aqueous environment. Graphene sheets typically decorated with epoxy (GO-O), and hydroxyl (GO-OH) hydrophilic functional groups can reduce apparent hydrophobicity.

Using molecular dynamics (MD) simulations the influence of the functional groups on adsorption of PTX anticancer drug molecules, adsorption energy, and the average distance of drug molecules from surface were evaluated. Simulations were conducted using the LAMMPS software package.

The results showed when the functional groups exceeded the critical value (18%), the number of atoms with the same partial charge in GO-OH system were more than that of GO-O surface. Therefore with an increase in the repulsion forces, the molecule distance became longer due to compressive surface stresses induced in GO-OH system. Furthermore, deformation of surface will result in an increase in the distance of PTX-GO.

Our findings suggested that type of functional groups affecting adsorption of paclitaxel on GO surface was important in drug delivery system. Moreover, the critical value of functional groups can have useful medical applications as in drug delivery systems.