Applied Surface Science, Vol.473, 31-39, 2019
Functions achieved by the hyaluronic acid derivatives coating and hydroxide film on bio-absorbed Mg
Plasma electrolytic oxidation (PEO) treatment is a traditional method to improve low corrosion resistance of absorbable magnesium. However, the ceramic porous film by PEO causes local corrosion and is highly brittle, so it must be improved by additional layers to seal the pore. In the present study, a hydrophilic surface was obtained by PEO with a biosynthesized natural material as hyaluronic acid (HA) and Carboxymethylcellulose (CMC) to improve bonding function. The HA on Mg yielded dense particles in microns, and HA on the PEO formed nano-crystals. The result of the electrochemical corrosion test indicated that the initial corrosion resistance was significantly improved by the HA coating. Specifically, HA and CMC on PEO reacted with Ca in similar body fluids, and this enabled quick self-healing through the scratch test. These results ultimately aided in cell differentiation and proliferation. The thin layer of Mg-HA without PEO was peeled off at the implantation in rat femur and local and persistent corrosion occurred. Finally, the PEO + HA displays a bi-layer structure and self-healing ability, and thus, it contributed to delay the initial erosion of implantation and to the stable formation of the new bone by maintaining the screw shape to heal the defective part of the bone.