Using density functional theory, noncovalent interactions and two mechanisms of covalent functionalization of drug 2-methoxyestradiol with functionalized carbon nanotube (CNT) have been investigated. Quantum molecular descriptors of noncovalent configurations were studied. It was specified that binding of drug 2-methoxyestradiol with functionalized CNT is thermodynamically suitable. COOH functionalized CNT (NTCOOH) has more binding energy than COCl functionalized CNT (NTCOCl) and can act as a favorable system for 2-methoxyestradiol drug delivery within biological and chemical systems (noncovalent). NTCOOH and NTCOCl can bond to the OH group of 2-methoxyestradiol through OH (COOH mechanism) and Cl (COCl mechanism) groups, respectively. The activation energies of two pathways were calculated and compared with each other. The activation energy related to COOH mechanism is higher than that related to COCl mechanism and therefore COCl mechanism is suitable for covalent functionalization. These results could be generalized to other similar drugs.

Mohammad Arab, Ali Morsali, Mohammad M. Heravi, and S. Ali Beyramabadi