Nanoscale Coordination Polymers for Synergistic NO and Chemodynamic Therapy of Liver Cancer

Nitric oxide (NO) induces a multitude of antitumor activities, encompassing the induction of apoptosis, sensitization to chemo-, radio-, or immune-therapy, and inhibition of metastasis, drug resistance, angiogenesis, and hypoxia, thus attracting much attention in the area of cancer intervention. To improve the precise targeting and treatment efficacy of NO, a glutathione (GSH)-sensitive NO donor (1,5-bis[(l-proline-1-yl)diazen-1-ium-1,2-diol- O²-yl]-2,4-dinitrobenzene, BPDB) coordinates with iron ions to form the nanoscale coordination polymer (NCP) via a simple precipitation and then partial ion exchange process. The obtained Fe(II)-BNCP shows desirable solubility, biocompatibility, and circulation stability. Quick NO release triggered by high concentrations of GSH in tumor cells improves the specificity of NO release in situ, thus avoiding side effects in other tissues. Meanwhile, under high concentrations of H₂O₂ in tumors, Fe²⁺ ions in BPDB-based NCP, named Fe(II)-BNCP, exert Fenton activity to generate hydroxyl radicals (·OH), which is the main contribution for chemodynamic therapy (CDT). In addition, ·O₂^- generated by the Haber-Weiss reaction of Fe²⁺ ions with H₂O₂ can quickly react with NO to produce peroxynitrite anion (ONOO^-) that is more cytotoxic than ·O₂^- or NO only. This synergistic NO-CDT effect has been proved to retard the tumor growth in Heps xenograft ICR mouse models. This work not only implements a synergistic effect of NO-CDT therapy but also offers a simple and efficient strategy to construct a coordination polymer nanomedicine via rationally designed prodrug molecules such as NO donors.