The scrutinised DFT and MD studies on the adsorption of D-penicillamine drug on γ-Fe2O3 nanoparticle as a highly efficient carrier

We have theoretically explored the adsorption behaviour of D-penicillamine (PEN) on the surface of magnetic nanoparticle (NP) (γ-Fe2O3) with quantum mechanics calculation and molecular dynamics (MD) simulation. Possible molecular configurations between the PEN and γ-Fe2O3 NP were examined by density functional theory (DFT) using Fe6(OH)18(H2O)6 ring cluster. The stability of optimised complexes was determined on the basis of relative adsorption energy (ΔEads). The atoms in molecule (AIM) theory was employed to gain an in-depth understanding of the intermolecular interactions. From the DFT calculations, the adsorption of PEN on the magnetite NP surface was exothermic and thermodynamically stable. The AIM results indicated that drug was adsorbed molecularly via hydrogen bonds to the surface of the NP. The electronic structure analysis of PEN showed that the structure of the drug molecule did not change considerably during the adsorption process. Moreover, MD simulation was performed to study the dynamics and diffusion of the drug molecule. The obtained results of interaction energies and binding free energies indicated that the PEN/γ-Fe2O3 complex had good stability in the solution phase. The diffusion of drug molecule into the γ-Fe2O3 surface was slow, which is a crucial factor for the controlled drug releases.