8-Hydroxyquinoline functionalized covalent organic framework as a pH sensitive carrier for drug delivery.

A porous 8-hydroxyquinoline functionalized organic covalent framework (named COF-HQ) was synthesized. The as-prepared COF-HQ showed stable crystal structure, suitable pore size, excellent dispersibility in physiological solution and pH sensitivity, which would be employed as a potential nanocarrier for drug transport and controlled release. The drug loading experiment with 5-Fluorouracil (5-FU) as the model molecule proved that the drug loading capacity of COF-HQ was significantly improved due to the introduction of quinoline groups. The drug release profiles of 5-FU from 5-FU loaded COF-HQ (termed 5-FU@COF-HQ) under different pH showed that its release was controlled by pH owing to the pH sensitivity of conjugated nitrogen atoms from quinoline groups and CN. The in vitro hemolysis and in vivo biocompatibility experiments further verified the good biocompatibility of COF-HQ. Importantly, 5-FU@COF-HQ-treated B16F10 cell-induced tumor models showed that 5-FU@COF-HQ displayed enhanced anti-tumor efficacy than other groups. These results suggested that the drug-loading COF-HQ delivery system showed the potential for effective cancer therapy with advantages of high drug loading, good biocompatibility and the pH-sensitive release of the tumor microenvironment. Overall, our research provided a new functionalized COF-HQ drug delivery system, which further expanded the application of COFs as carriers in the field of cancer treatment.