Noncovalent interaction assisted fullerene for the transportation of some brain anticancer drugs: A theoretical study.

The treatment of brain cancer like glioblastoma multiforme often uses chemotherapeutic drugs like temozolomide, procarbazine, carmustine, and lomustine. Fullerene loaded with these drugs help to cross the blood brain barriers. The adsorptions of the four drug molecules on the surface of the fullerene are studied mostly by using density functional theory (DFT) based method at the M06-2X/6-31G(d) level of calculations. In all four cases, the estimated interactions are noncovalent type and the average adsorption energy lies in between -5 and -11kcal/mol in the gas phase. In the aqueous and protein environment such interactions are weakened further. The binding affinity is further assessed by performing MP2 based calculations to provide interaction energies with a reasonable accuracy. Stabilities and reactivities of the drug adsorbed fullerene complexes are determined from chemical reactivity descriptors. The attached drug molecules increase the polarity of the pristine C60 thus facilitating the drug delivery within the biological systems. The semiconducting behavior of C60 is retained in the C60-drug composite systems. The computed DOS, IR, UV spectra, and molecular orbitals in the vicinity of Fermi level are analyzed to reveal the nature of the noncovalent interactions between C60 and drug molecules. The Wiberg bond order values are used to estimate the strength of the adsorption of the drug molecule on C60. In all four C60-drug interactions, the chemical characteristics of the drug molecule are least perturbed by the C60 moiety thereby suggesting it to be a good carrier for the delivery of these brain anticancer drug molecules to the target cells.