A quantum chemical study on the magnetic nanocarrier-tirapazamine drug delivery system

Magnetic nanoparticles are among the most important carriers for the delivery of anticancer drugs. Four important noncovalent interactions between tirapazamine anticancer drug (TPZ) and magnetic nanoparticle Fe$_6$(OH)$_{18}$(H$_2$O)$_6$ (MNP) have been examined by using density functional theory (DFT). Important interactions are those where the drug approaches the magnetic nanocarrier via NH$_2$ (MNP/TPZ1), NO (MNP/TPZ2-3) and intraring N-atom (MNP/TP4) functional groups. The negative values of binding energies and quantum molecular descriptor showed that these interactions contribute to the stability of the system. By increasing the temperature, TPZ can bond to MNP through NH$_2$ (NH$_2$ mechanism), NO (NO mechanisms) and intraring N-atom (N mechanism) functional groups. The activation parameters of four mechanisms were evaluated using quadratic synchronous transit method. Relative energies indicate that the product of the NH$_2$ mechanism is more stable but is produced more slowly (thermodynamic product). In contrast, the products of the NO mechanisms are kinetic products.