The interaction between a boron-based Zn@B38 superatom and five drugs, including cisplatin (DDP), 5-fluorouracil (FU), mercaptopurine (MP), hydroxyurea (HU) and nitrogen mustard (CM) have been investigated. The adsorption of these anticancer drugs onto Zn@B38 reduces the energy gap of this superatom. Except for DDP, these drugs exhibit strong covalent interaction with the vertex of Zn@B38 because the lone pair of N/O atom of FU, MP, HU, and CM can fill into the empty atomic orbital of the electron-deficient boron atom of Zn@B38 to form polar covalent bonds, resulting in the charge transfer from drugs to Zn@B38. Hence, the adsorption energies of drug@[Zn@B38] (drug = FU, MP, HU, and CM) are −37.67 ∼ −57.21 kcal/mol, but can be significantly decreased to −8.63 ∼ 5.48 kcal/mol upon protonation, suggesting that these drugs can be efficiently adsorbed by the Zn@B38 carrier in neutral aqueous solution but are easily released in the acidic tumor microenvironment.
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