Synthesis of metal–organic-frameworks on polydopamine modified cellulose nanofibril hydrogels: constructing versatile vehicles for hydrophobic drug delivery

Direct loading of hydrophobic drugs into hydrophilic nanocellulose based hydrogels remains challenging. Herein, polydopamine was first auto polymerized on the surface of cellulose nanofibril (CNF) hydrogel to obtain PCNF composite hydrogel. Then, zeolitic imidazolate frameworks-8 (ZIF-8) nanoparticles were in situ grown in the structure of PCNF composite hydrogel. Hydrophobic drug curcumin (Cur) was encapsulated into the hydrogel with loading ratio as high as 4.5 wt%. The mechanical strength of the ZIF-8@PCNF composite hydrogel was 2.75 times higher than that of the CNF hydrogel. Moreover, the composite hydrogel presented controlled drug delivery properties. The drug delivery time of ZIF-8@PCNF composite hydrogel was 3.57 times and 5.35 times longer compared to the PCNF composite hydrogel and CNF hydrogel, respectively. Anomalous transport was found to be the main drug release mechanism. In addition, (ZIF-8@PCNF)-Cur composite hydrogel exhibited anticancer effects toward HepG2 cells. Therefore, this novel ZIF-8@PCNF composite hydrogel is expected to be a very promising biomaterial for drug delivery applications.