Fabrication of microwave-sensitized nanospheres of covalent organic framework with apatinib for tumor therapy

A new nanocomposite of hollow covalent organic framework (COF) conjugated with the apatinib (AP) and loading microwave-sensitizer (ionic liquid, IL) was prepared by layer by layer (LBL) method and hyaluronic acid (HA) coating, named as COF-AP-IL@HA. AP loading rate in COF hollow-spheres (∼30 nm shell thickness) was ∼40.3%, due to the interactions of hydrogen and π-π bonds between AP and COF shell, and acidic environment destroyed COF structure, promoting AP release. Microwave sensitization of loaded IL in COF hollow-spheres could enhance the microwave heat-effect, and combined AP therapeutic ability, leading to their higher inhibitation on tumor, due to targeting ability of HA and the local release of apatinib. 88.9% of inhibition rate of COF-AP-IL@HA under microwave on the in vivo tumor was significantly higher than those without microwave (12.3%) and COF-IL@HA with microwave (37.5%), indicating a synergism of sensitized microwave hyperthermia and AP therapy on the reduced expression of VEGF via the downregulation pathway of hypoxia inducible factor. These results indicated that COF-AP-IL@HA was potential to the application in the combination therapy of tumor of the sensitized microwave hyperthermia and apatinib.