In this study, density functional theory calculations were conducted to investigate the interaction and electronic properties of two anti-cancer drugs, doxorubicin and melphalan, using pristine and Cr-doped nanodiamonds. The interaction energies of doxorubicin and melphalan onto pristine nanodiamond were calculated to be − 259.584 kJ/mol and − 251.286 kJ/mol, respectively, indicating an exothermic process. Doping the nanodiamond with Cr enhanced the interaction, with energies of − 297.786 kJ/mol for doxorubicin and − 286.694 kJ/mol for melphalan. Chemical hardness, highest occupied molecular orbital, and lowest unoccupied molecular orbital analysis showed that both doped complexes with Cr were relatively soft, with nanodiamond-doxorubicin being softer than nanodiamond-melphalan. The high dipole moment of doped nanodiamond-Cr-doxorubicin 9.979 Debye compared to nanodiamond-doxorubicin 3.989 Debye suggests that doped nanodiamond-doxorubicin is more interaction. Thermodynamic calculations revealed the spontaneity and stability of these complexes. Overall, the results demonstrate the enhanced drug loading capacity of Cr-doped nanodiamonds and their potential as drug delivery carriers for doxorubicin and melphalan.
