Chemotherapy drug temozolomide adsorbed onto iron-oxide (Fe3O4) nanoparticles as nanocarrier: A simulation study

Abstract

The adsorption of different temozolomide concentrations onto 1 to 6.9 nm Fe3O4 nanoparticles (to be employed as nanocarriers) is investigated within a molecular dynamics study and Monte Carlo simulated annealing scheme. Bonding modes are investigated with reference to chemisorption, physisorption as well as hydrogen bonding in the context of bond strength (binding energy) as a function of both the temozolomide molecule's loading as well as a change in nanoparticle size from 1 nm up to 6.9 nm. Density functional theory (DFT) simulations are also performed to investigate the conditions for charge transfer from the temozolomide surfactant via the highest occupied molecular orbitals (HOMO), lowest unoccupied molecular orbitals (LUMO) as well as the electrostatic potentials. From this the preferential sites for both electrophilic and nucleophilic attacks were calculated. It is shown that the most reactive sites are the oxygen (O-17 and O-8) as well as nitrogen (N-12) atomic sites which was confirmed by the Monte Carlo molecular dynamics calculations to be reactive with the Fe2+ and Fe3+ ions of the NP surface. Interaction with the O-8 oxygen site was not as prominent as originally anticipated and this was shown by observing the positions of the HOMO and LUMO isosurfaces that were more prominently centred on the O-17 site.