The absorption mechanism of 5-fluorouracil on MnO2-based nanostructures by DFT calculation and experimental analysis

It is of great significance to explore the mechanism of drug molecules hiking on nanomaterials for targeted delivery. In this study, we evaluated the interaction potential of three manganese dioxide (MnO2) nanostructures with 5-fluorouracil (5-FU) using a density function theory (DFT) framework and dispersion correction (D3BJ) and conducted experimental verification. All possible adsorption modes and locations are predicted by electrostatic surface potential (ESP) and van der Waals force calculations. The charge transfer between molecular groups was estimated by electron density difference (EDD). The energy-favorable model of 5-FU interaction with distinct MnO2 crystals is investigated by using partial density of states (PDOS). Further, the quantum theory of atoms in molecules (QTAIM) calculation and independent gradient model based on Hirshfeld partition (IGMH) analysis were applied to reveal the interaction details. Our results suggest that 5-FU can be absorbed at different positions on the surface of MnO2, in which the O-adsorption mode is mainly dominated by hydrogen bond, while the Mn-adsorption mode is dominated by coordination interaction. Besides, the dispersion-dominated interaction cannot be ignored. DFT calculations show that MnO2 nanostructures are promising drug carriers, and β-MnO2 exhibits better adsorption behavior than the other two crystals. Experimental study showed that the 5-FU drug loading of β-MnO2 (28.82%) was higher than that of α-MnO2 (16.72%) and δ-MnO2 (21.69%).