Tannic acid-based nanogel as an efficient anti-inflammatory agent

Biologically produced reactive oxygen species (ROS) are important signaling molecules in the human body. Despite their importance under normal conditions, abnormal overproduction of ROS under unbalanced or irregular homeostasis can cause severe inflammatory diseases. Various antioxidants have been developed in the biomedical field to resolve high levels of ROS; however, high doses of natural antioxidants such as polyphenol can induce side effects on health. Further, synthetic antioxidants are still controversial in regards to their safety and their complicated synthesis. Inspired from our previous work, a nitric oxide-scavenging nanogel designed for treating rheumatoid arthritis, we report herein a biocompatible tannic acid (TA)-based nanogel as an effective ROS scavenger. A polymeric phenylboronic acid-tannic acid nanogel (PTNG) was prepared by simply mixing through to the formation of phenylboronic ester bonds between polymeric phenylboronate and TA. We focused on the reaction of phenylboronic ester with H2O2, which readily consumes H2O2 molecules, and applied it as an antioxidant. In addition, TA is a well-known antioxidant, specifically a free radical scavenger; thus, we expected combinatory ROS scavenging effects for PTNG. Various ROS scavenging assays revealed the significant antioxidant effects of PTNG. Under an induced inflammation model in vitro, our PTNG showed high biocompatibility as well as strong anti-inflammatory effects. Furthermore, in the zymosan-induced peritonitis mouse model, a representative acute inflammation model in vivo, PTNG reduced significant neutrophil recruitment and pro-inflammatory cytokines, indicating successful alleviation of inflammation. On the basis of these results, we suggest that PTNG has great potential as an antioxidant and should find application in the treatment of further ROS-overproducing inflammatory diseases.