Investigation of the quantum molecular descriptors in reactivity of Carmustine drug with boron nitride nanotube by DFT approach

In this study, a quantum mechanical study for the interaction of the Carmustine (BCNU) with the (6, 0) zigzag single-wall boron nitride nanotube (SWBNNT) is studied by means of density functional theory (DFT) calculations at the B3LYP/6-31G* level of theory. Carmustine is an effective drug for the treatment of brain tumors which is used in chemotherapeutic [1]. It is well known that boron nitride nanotubes are more appropriate nanotubes for biomedical applications [2]. The difference between EHOMO and ELUMO for drug molecule and nanotube is calculated and the value of |EHOMO (SWBNNT)-ELUMO (BCNU)| and |EHOMO (BCNU)-ELUMO (SWBNNT)| energies are obtained 4.270 eV and 5.497 eV, respectively. The obtained results reveal that the electron density transfer can be performed between the HOMO of nanotube and the LUMO of Carmustine. Also, the HOMO and LUMO orbitals for BCNU/SWBNNT complex are shown in Fig. 1. As can be seen from Fig. 1, the HOMO is mainly localized at nitrogen atoms of the nanotube (panel (a)) while the LUMO is on the BCNU (panel (b)) in BCNU/SWBNNT complex. Also, the values of Eg and  decrease in complex by the adsorption of drug molecule on the nanotube surface (Eg SWBNNT =4.88 ev Eg BCNU/SWBNNT =4.59 ev, BNNT = 2.44 ev and  BCNU/SWBNNT = 2.29 ev). The lowering of energy gap and global hardness indicates that the reactivity of the system is increased. Electronegativity (χ) and electronic chemical potential (χ = -) identify the direction of electron flow. When the BCNU molecule and SWBNNT are brought together, electrons will flow from that of higher  ( SWBNNT= -4.23 ev) to that of lower  (BCNU=-4.84 ev).