Comparison of loading and unloading of different small drugs on graphene and its oxide

Abstract Adsorption of drugs on graphene nanosheets can prevent enzymatic degradation. However, the mechanisms of graphene-drug complex permeating into the cell interior and the subsequent drug release remain unclear. In this work, we performed molecular dynamics simulations to investigate the drug delivery capability of pristine graphene (PG) and its oxide (graphene oxide, GO). Three drugs, namely, primidone (PRI), pregabalin (PRE) and bortezomib (BOR) were adopted as they have different molecular size and polarity. The results show that the adsorption intensity of GO is much stronger than that of PG, due to the electrostatic interactions or hydrogen bonding originated from the oxygen-containing groups on GO, which is confirmed by free energy calculations. And therefore, drug molecules are difficult to leave from GO surface after the complexes enter the membrane. Compared with PRE and BOR, PRI molecules are more suitable to be loaded and unloaded by both PG and GO. The results indicate that graphene and its oxide served as substrates to deliver particular drugs is theoretically feasible.