Nitrogen-doped carbon-ZnO heterojunction derived from ZIF-8: a photocatalytic antibacterial strategy for scaffold

Antibacterial property is urgently needed in scaffold-induced bone regeneration. Zinc oxide (ZnO) as a photocatalyst enables to produce photoexcited electron-hole pairs to catalyze reactive oxygen species (ROS) generation, which triggers the peroxidation and consequently apoptosis of bacteria. However, the fast recombination of electron-hole pairs and the wide band gap of ZnO restrict the full play of its antibacterial property. Herein, a nitrogen-doped carbon-ZnO (NC-ZnO) heterojunction derived from metal organic frameworks was synthesized by direct carbonization. On one hand, the N-doped C in NC-ZnO acted as electron acceptors to trap photoexcited electrons in conduction band of ZnO, which improved the separation efficiency of electron-hole pairs. On the other hand, the N-doped C with high absorption coefficient enabled NC-ZnO to possess a relatively narrow band gap and wide light absorption range compared with ZnO. The obtained NC-ZnO heterojunction was then introduced into poly-l-lactic acid (PLLA) scaffold to construct a photodynamic antibacterial platform. The results showed that NC-ZnO endowed the scaffold with excellent photocatalytic activity and greatly stimulated the production of ROS. The antibacterial tests suggested that the PLLA/NC-ZnO scaffold possessed robust antibacterial activities with 99.9% antibacterial efficiency toward Escherichia coli, which was increased by 113.9% compared with PLLA/ZnO scaffold.