BONDING OF PHOSPHORAMIDES ONTO B-C59 NANOPARTICLE AS DRUG DELIVERY SYSTEMS

The structures of boron-doped fullerene B-C59 (1) as a drug delivery system, two phosphoramides (2 and 3) which are analogous to the cyclophosphamide anticancer prodrug as well as their covalently bonded structures to B-C59 (4 and 5) were optimized by DFT computations at B3LYP level of theory using 6-31G(d) basis set. Comparing compounds 4 and 5 reveals that the bromo derivative (-25.7425 kcal/mol) is more stable than its chloro analogue (-24.2709 kcal/mol). The dipole moments of isolated drugs have almost half values compared with those of their related covalently bonded compounds with B-C59 reflecting attachment of drugs to the B-C59 considerably enhances the polarity of the whole systems which is a desired property for drug delivery in biological media. The ΔGinteraction value is slightly more negative for compound 4 relative to that of 5 and the attachment of both drugs on the surface of B-fullerene is exergonic (ΔGinteraction < 0) that means formation of compounds 4 and 5 are spontaneous reactions. Similarly, the ΔHinteraction values are negative for both compounds 4 and 5 reflecting these interactions are exothermic (ΔHinteraction < 0). The density of states (DOS) spectra disclose that there are very strong hybridizations between the orbitals of B-C59 (1) and the drug molecules (2 and 3) so that they illustrate combinations of the spectra of the drugs and B-C59. Therefore, great interactions are happened quantitatively in terms of binding energies. The oxygen atoms of P=O and P–O bonds reveal χ values about 5.0 and 10.0 MHz, respectively that may be because of more positive oxygen atoms in P–O bonds that have a greater interaction with EFG tensor. Moreover, the phosphoryl O1 atoms of compounds 4 and 5 show greater NQCCs compared with those of isolated drugs confirming the O1 environment has become more asymmetric upon its attachment to the B atom of B-C59 particle. The 35Cl, 37Cl and 79Br, 81Br nuclei reveal NQCCs of about 70, 55 and 500, 420 MHz, respectively.

Keywords:

B-C59 nanoparticle , Phosphoramide , DFT computation , Drug delivery , NQR