Poly(tannic acid) nanocoating based surface modification for construction of multifunctional composite CeONZs to enhance cell proliferation and antioxidative viability of preosteoblasts

Ceria (CeO 2 ) based materials possess many antioxidant enzyme-like activities and unique properties for bone repair, but their free radical scavenging function is still insufficient. In order to deal with the complex oxidative stress environment in bone repair, multifunctional composite CeO 2 nanozymes (CeO 2 NZs), featuring multiple antioxidative properties, were constructed via surface modification on CeO 2 NZs with nanoscale poly(tannic acid) (PTA) coatings. Moreover, we adjusted pH conditions (ranging from 4 to 9) to effectively control the formation and antioxidative properties of PTA coatings on CeO 2 NZ surfaces. Here, the physical properties of this novel inorganic and organic composite antioxidant, such as surface morphology, particle size, crystal structure, surface charge and element composition, were thoroughly characterized. The PTA/CeO 2 NZs showed obvious coating morphology under weak acid conditions (pH = 5-6), and the PTA layer at pH = 5 is about 1 nm in thickness. Compared with untreated CeO 2 NZs, the PTA/CeO 2 NZs showed stronger SOD-like activity and obviously higher free radical scavenging rate (for both ABTS + &z.rad; and DPPH&z.rad;).Notably, this composite antioxidative nanozyme not only exhibited favorable cell proliferation of preosteoblasts (MC3T3-E1) but also provided strong antioxidative property to maintain cell vitality against H 2 O 2 induced oxidative damage. In particular, this study provides new insights into the designing of surface polyphenolic coatings at the nanoscale, and these multiple antioxidative properties shown by PTA coated CeO 2 NZs make them suitable for protecting cells under the oxidative stress environment. To meet the requirements for anti-OS bone repair, multifunctional composite ceria nanozymes (CeO 2 NZs) were constructed by PTA coating modification on the CeO 2 NZ surface with pH regulation.