Flower-shaped covalent organic framework synthesis and its anticancer drug delivery application

Fabrication of covalent organic frameworks (COFs) at room temperature is necessary due to their easy preparation, practical scale-up, and low cost to overcome the limitations of solvothermal and high-temperature synthesis. Herein, we fabricated flower-shaped COFs (FSCOFs) that were synthesized in various ratios of orthoxylene and butanol mixture solvents. The FSCOFs exhibited excellent crystallinity with a pore size of approximately 10 nm, which was confirmed by PXRD and BET measurements. To utilize the FSCOFs as a drug carrier, doxorubicin (DOX) was loaded, followed by encapsulation of hyaluronic acid to increase the colloidal stability of FSCOFs in a physiological environment (FSCOFs-DOX-HA). The encapsulation efficiency and the drug loading capacity of FSCOFs-DOX-HA were 21.23 % and 29.82 %, respectively. Moreover, 92 % and 59 % of DOX is released in acidic environments and elevated GSH environments, proving the sensitivity of the FSCOFs as carriers. The excellent drug release mechanism of FSCOFs-HA-DOX is demonstrated by FSCOFs imine nitrogen protonation under acidic environment confirmed by its zeta potential changes under various physiological environments. The designed FSCOFs-DOX-HA was demonstrated to be a pH-sensitive drug carrier to deliver anticancer drugs into cancer cells. The MTT and drug internalization data demonstrated sustained DOX release from FSCOFs-DOX-HA. Finally, the real-time fluorescence demonstrates the effectiveness of the FSCOFs-DOX-HA upon cellular uptake and release of the anticancer drug. Thus, the FSCOFs system reported here opens a new path in COF research for drug carrier systems.