Theorical investigation of adsorption mechanism of doxorubicin anticancer drug on the pristine and functionalized single-walled carbon nanotube surface as a drug delivery vehicle: A DFT study

In this work, interaction and bond properties of anticancer drug doxorubicin (DOX), armchair single-walled carbon nanotube (SWCNT), and hydroxyl- and carboxyl-functionalized SWCNT (ƒ-SWCNT) have been investigated based on DFT theory to design, improve and expand carbon nanotube (CNT) drug carriers which is applied in biomedical systems such as drug delivery systems. Geometrical, structural, electrical, bonding and thermodynamic properties as well as optimized geometry, adsorption energies, quantum molecular descriptors, topological parameters and frontier molecular orbitals of different drug arrangements on CNT at the highest equilibrium at WB97XD/6–31 + G (d, p) level of theory at aqueous and gas phases were explored. Our calculations showed that hydrogen bonds between active sites of DOX molecules and hydroxyl- and carboxyl-functionalized CNTs played a more important role than those with pristine CNTs in the adsorption and fixation of the studied complexes as well as their thermodynamic energy. Using quantum theory of atoms in molecules (QTAIMs) method, intermolecular interactions and corresponding parameters at critical bonding points in aqueous and gas phases were also investigated. Evaluation of the results obtained from the natural bond orbital (NBO) analysis showed that the direction of electron movement was generally from drug molecule to CNT.