Co-loaded CNT having adjustable Co2+/Co3+ ratio endows PLLA bone scaffold with ROS-scavenging

Co-loaded CNT with high Co 2+ content of 61.07% exhibited enhanced nanozyme activity. • P2 possessed a safe Co-ion release content far below the threshold of 20 ppm. • P2 exhibited good well-rounded properties and excellent anti-inflammatory activity. Excessive reactive oxygen specie (ROS) is not conducive to bone repair, which is prone to generate during the initial hematoma inflammatory phase following poly( L -lactic acid) (PLLA) bone scaffold implantation and the potential inflammation caused by its acidic degradation products. This study proposed introducing cobalt (Co)-based nanozyme into the PLLA scaffold, and focused on improving the dispersion between nanozyme and the PLLA matrix as well as enhancing the activity of nanozyme itself for efficiently scavenging ROS. The Co was loaded on the surface of carbon nanotube (CNT) for achieving uniform dispersion, and then calcined under different atmospheres for enhancing nanozyme activity via regulating the Co 2+ /Co 3+ ratio and optimizing the electronic structure. It was found that the nanozyme that was calcined in an N 2 atmosphere followed by phosphorylation exhibited a superior ROS-scavenging ability, which was attributed to its high Co 2+ content of 61.07% that facilitating the redox cycling and the optimization of its electronic structure by P doping. As a result, the composite scaffold (P2) at a nanozyme loading of 2 wt% possessed superior intracellular ROS-scavenging ability and downregulation of key inflammatory cytokines compared to the pure PLLA scaffold. It also possessed good cytocompatibility for cell adhesion and proliferation, and exhibited upregulated expression of the pro-angiogenic VEGF factor. Download: Download high-res image (228KB) Download: Download full-size image Co-based nanozyme was engineered by promoting dispersion and optimizing the Co 2+ /Co 3+ ratio for highly efficient SOD and CAT, and was used to endow the PLLA bone scaffold with good ROS-scavenging and cytocompatibility.